I. 'IHIlllir df o^.cf "mi, m ^

THE

RAY SOCIETY.

INSTITUTED MDCCCXLIV.

This volume is issued to the Subscribers to the Ray Society for the Year 1882.

LONDON

MDfiCCLXXXIII.

MONOGRAPH

OF THE

BEITISH APHIDES

VOL. IV.

GEORGE BOWDLER BUCKTON,

FELLOW OF THE ROYAL, LINNEAN, AND CHEMICAL SOCIETIES OF LONDON ;

CORRESPONDING MEMBER OF THE ACADEMY OF NATURAL

SCIENCES, PHILADELPHIA.

~ifvK\ai ixev /xixpal p.dKa juvpiai, avrap eKao-njv

S&KVei \fiv\\iSCuiv ixiKftOTtpoiv aye'Aij' >pv\\iS(iov yei'edi' eVep' av woKv /xeiova Sanvei

^uAAi'St"' oil Aijyei trpayp.' e's aneipov iov. —

MeAeaypov, wj Sd rives, 2Tp«i/uo6ou'

LONDON: PRINTED FOR THE RAY SOCIETY.

MDCCCLXXXIII.

m

0 war with falsehood to the knife, And not to lose the good of life. * # * *

As far as might be to carve out Free space for every human doubt, That the whole mind might orb about.

To search thro' all I felt or saw,

The springs of Life, the depths of awe,

And reach the law within the law.

Tennyson— The Two Voices.

PRINTFD BY J. E. ADLARD, BARTHOLOMEW CLOSE.

7U62UG9901

PEEFACE.

On introducing this concluding volume to the reader, I tender my sincere thanks to the Members of the Council of the Ray Society for undertaking the publication of my Monograph, and for the courtesy which they have shown me in fulfilling my wishes as to the form it should assume.

Prof. Helmholtz well remarks that " The materials of a monograph must be united by a logical process ; and the first step is to connect like with like, and to elaborate a general conception embracing them all." Again, elsewhere, "A digest or catalogue may be likened to a good lexicon ; with which almost a tyro of the present day can achieve results in the interpretation of the classics, which an Erasmus, with the erudition of a lifetime, could hardly attain."

Some may perchance think that this Monograph has attained proportions unnecessarily large. The general reader, on the one hand, may take exception to its detail. The competent biologist, with more truth perhaps, may complain of omissions as well as com- missions. The first may call to remembrance and apply the causticity of Montaigne when he says, " The trade of the rhetorician is to make things appear and

VI PKEFACE.

seem great, just as a shoemaker can make great shoes for little feet."

An attempt has been made so to blend the life-history of Aphides with their morphology, as to render the subject not wholly uninteresting to the general reader, and yet to furnish details necessary for the systematist : but the latter may reasonably ask that the facts shall not be put before him in a form unnecessarily dry.

The depths of Biology are as unfathomable as those of any other science. The long list of authors I furnish at the end of this volume, though far from exhaustive, will show how much attention has been already paid to this group of insects ; and yet I am sensible of many omissions, and that much has yet to be discovered with reference to my subject. It would almost seem that more may be written on this one single insect family than on the life-history of a family of the carnivorous Vertebrata ; — we may instance the Felida3. Indeed, several years' study is required to pro- duce a complete life-history of some insects, and they may require special treatises to exhaust the subject.

Through the kindness of M. J. Lichtenstein, I am enabled to give a short but compendious history of the grape-vine pest, Phylloxera vastatrix. His researches and familiarity with the whole tribe will make his observations acceptable to all.

Although not strictly within the province of a treatise on British Aphides, a chapter has been devoted to the question of the general existence of Aphides in early geological times. The author has freely consulted several important memoirs of Prof. Oswald Heer, and also his valuable treatise on the ' Primeval World of Switzerland.' .Much help lias likewise been obtained

PREFACE. Vll

from Mr. Samuel Scudder's numerous published papers on Fossil Insects; particularly from those sections bearing on the fossil Aphides found in the beds of the Florissant basin of Colorado. This gentleman has most liberally allowed me to draw from some of his plates which have not yet been published. Although these forms are American, they have characters almost identical with our recent European genera.

To these sections I have also added a short account of some of the Aphides which have been included in masses of amber.

The author trusts that the preliminary remarks of this and the preceding volumes will be a sufficient acknowledgment of the sources from which much of his information has been drawn.

Towards the close of this volume I have thrown together some of the principal known facts relating to the reproduction and embryology of Aphis ; and by way of introducing this subject, I have attempted a sketch bearing on the general growth of the ovum of insects. I wish here to acknowledge my indebtedness to the works of Dr. Allen Thomson, Professors Huxley, Forster, and Balfour, Ray Lankester, Ernst Haeckel, Dr. A. Brandt, E. Balbiani, and others. The late Prof. Balfour's recent treatise on ' Comparative Embryology ' is a mine of wealth to all biologists.

In my former volumes I expressed, as strongly as I was able, my obligations to many friends ; and I will not here repeat my thanks. One gratification in the study and illustration of natural phenomena is a con- tinual growth of genial correspondence with those of kindred thoughts and tastes.

I must here, specially offer my thanks to Prof.

Vlll PREFACE.

Huxley, who kindly made some valuable criticisms on reading my proofs on the ' Morphology and Reproduction of Aphis ; ' and also to Prof. Thomas Wiltshire and Prof. Rupert Jones, both of whom have suggestively helped me to get all my four volumes through the press.

The subscripture to the Greek verse on my title page is very obscure : and it will invite and test the ingenuity of many, as to whether the author be ancient or modern.

Recently I have received from an anonymous writer, who shrouds himself in euphonious but somewhat " stiff " Greek, a witty suggestion as to the vexed derivation of Linneus' word Aphis. It may be fairly inferred that both these effusions are the product of the same, or of kindred spirits.

'O boKifiuiraros rfjs (3a<TiXiKi)s eratpelas auvebpos Bu/crwi' ttoWci kcii /jivij/j^s a£(cz irepl twv acpiSwv eipr)K€v, a fxivroi irepl rov vvv/jaros oro^a^erat ov navTawafft niBavit, t))v 8k aXrjdi] ervfxoXoyiav iraph twv itaXaiwv riv\ earn' evpelv, os kv ro'ts drjpiaKols ovrw ypa(j)€i'

Y]prt£iv6r)$ OfiuXeKrpos avt)p rptsKaiBeiccnrrj^vs rrjTTirt'^ov irapeovTOS €(j)r)f.dadt] KaXos an(pvi' aXX'efik rov8e aej3ecr0e (pLXot woXv KaXXiov uirfvi', ?) yap iyoj \pvX\wv avrou-wopos eifAi rfpuiramros, irpdorap-^os 8e iretyvKa irpoavOpwiros TrporreXrjfos, TtapQevos t'jideos r', ov8ev ^aTewf ' Afpobirtjs, \pvXXi8i' <?k \pvXXu>v €k \pvXXi8iu)v re (ftVTevojp fivpia fivpiaKis tiktw, tu 8e r€Kv' eiririKTei [XvptaKis TroXXanXaaiov yevos, ibvirep eKncrrov dptTTTpa TOKevai <f>iXois Xa/uvpovs eviTt-qtfiv oburras v\piyoi'oy Trpoybtoiai, ra fieiora 8' 07rAdrep' aXlcijv fieiloai wpeo-fivrepois t<xa£era(, wot' es iineipov buKvov daKVopevov baKeiDV 8ukos ovirore Xt'/yet.

PEE PACE. IX

<pi>\ov b* w/i0j3i'|0ov Kai 7rafi<payov, ws 'F,pv<rl-%d(jjv, vv fiovov a.Xk))\<tiv <x\\' ai'dpo/ueov \poa bairrei alfiofiacbfi, tcnl Kapwbv airelpova y»7s epifiwXov* Toaoijt §' ctKafiarov Trporrarwp afia^oto yeredXrji ap'ov nacrt o-f/Saoros eyw yuciAa nayKaXoi cnrtyvs ; e£ kfiedev S' cupides Tropdi'iropes ovvo/i e^uvai vvv ert, 7T>7/i' aXiaorov oi^vpoiai f5poTO~i(riv.

The identity and unity of phenomena connecting the higher with the lower forms of living animals, is now too well acknowledged to want urging ; yet the words of Leon Dufour may be quoted in conclusion as apposite.

" Ce n'est pas seulement a rechercher et a con- naitre les productions naturelles qui par leur grandeur sont a la portee facile de ces sens, que l'homme avide d'instruction doit consacrer ses soins et ses loisirs ; il trouvera des sujets tout aussi dignes de son culte, dans les etres qui par leur petitesse occupent les derniers degres de Fechelle organique et semblent

d^fier son attention L'elephant massif,

l'orgueilleux Vir sapiens, n'ont pas plus couter au Createur, que l'impalpable byssus .... et la punaise."

Weycombe, Haslemere ; March 7th, 1883.

VOL. IV.

BRITISH APHIDES.

YOL. IV.

GENERAL SYNOPSIS.

Vol. I.

T Aphidin^;. . Upper wing with p^q a twice-forked M J cubitus ; under wing with two oblique veins. Antennse with 7 _ joints. a

l-M j

GENERA.		PAGE^
	,Absinthii Alliarige	. 151
	. 123
	Artemisiae	. 155
	Avellanae	149
	Carnosa	. 144
	Chelidonii	. 121
*	Cichorii	. 163
	Oircumflexa	. 130
	Convolvuli	. 148
	Cyparissiaa	. 113
	Dirhoda	. 132
	Fragariae	. 125
	Granai'ia	. 114
	Hieracii	. 126
	Jaceaa .	. 153
	Lactucse	. 139
	Longipennia	. 146
	Latea .	. 119
	Menthae	. 120
	Millefolii	. 127
I.	Muralis	. 157
HONOPHOBA. U	Olivata .	. 164
	Pelargonii .	. 136
	Pisi	. 134
	Polygoni	. 123
	R0S33	. 103
	„ var. gl	mca. 109
	Rosarum	. 150
	Rubi .	. 140
	„ var rufa	j, vol.
	iv, p. 105	,
	Scabiosae	. 112
	Scrophulariae	. 137
	Sisymbrii	. 160
	Solidaginis .	. 156
	Sonchi .	. 161
	Tanaceti	. 151
	Tanaceticola	. 159
	Tussilaginis	. 159
	,Ulmaria3 Urticaa .	. 134
	. 143;

VOL. IV.

BRITISH APHIDES.

Aphidin^e (continued).

GENERA.		PAGE,
f	Galeopsidis .	. 171]
Humuli	. Ififi
Phorodon. l j	„ var. Malabeb 168
c	Cerasi .	. 174
in. \	Gracilis	. 176
Myzus. « 1	Persicae	. 178
(	Ribis .	. 180
IV. f Drepanosiphum.- (.	Acerina	. 185
Platanoides .	. 183
Amphorophora. (.	Ampullata .	. 187
YI. C Megoura. i (.	Vicise .	. 188
	Vol. II.
	"Berberidis .	. 14
	Diantbi	. 15
YII.	Lactucae	. 10
Rhopalosiphum. A	Ligustri	. 13
	Nympbaese .	. 12
I	Ribis .	. 9	OQ
VIII. j Melanoxanthtjs. u{	Salicis .	. 21	o
(	' Caprese	. 27
IX. \	Foeniculi	. 26
SlPHOCORYNE. o .	Pastinaceae	. 24
(	^Xylostei	. 25
	rAbietina	. 43
	Acetosa3	. 80
	Amygdali	. 104
	Atriplicis	. 87
	Aucuparisa	. 76
	Bellis .	. 98
	Brassicao	. 33
	Cavdui .	. 92
	Crata)garia	. 37
X. Aphis. >	Cratasgi	. 35
Cucurbiti Edentula	. 56 . 39
V	Epilobii	. 71
	Euonymi	. 72
	Farfarea	. 68
	Hederse	. 75
	Hieracii	. 67
	Iustabilis	. 94
	Jacobffia)	. 79
	Labnrni	. 86
	^Lentiginis	. 59	)

GENERAL SYNOPSIS.

GENERA.

X.

Aphis

(continued).

Aphidin^;

(continued).

XL

Hyalopterus.

XII.

Chaitophorus.

XIII.

Pterocomma.

XIV. Cryptosiphum.

XY. Brachycoltts.

"Lychnidis Mali . MalvsB . Myosotidis Opima . Padi . Papaveris Pedicularis Penicillata Petasitidis Pruni . Pyraria Pyri . Rumicis Saliceti Sanibucaria Sambuci Scabiosse Sedi Sorbi

Subterranea Tanacetina Urticaria ^Viburni

f Aruudinis J Dilineatus J Eriophori | Melanocephalus

Pruni . LTrirhoda

C Aceris .

Betulse .

Capreaa •{ Leucomelas I Populeus | Populi . |J3alicivorus

< Pilosa .

j Artemisia

5 Stellaria?

Vol. III.

PAGE,

. 73

. 44

. 42

. 102

. 101

. 61

. 91

. 41

. 51

. 69

. 64

. 53

. 97

. 81

. 52

. 95

. 99

. 55

. 90

. 58

. 38

. 63

. 50

. 77

. Ill . 113 . 117 . 116 . 110 . 114

. 121 . 139 . 136 . 135 . 137 . 140 . 134

. 143

. 145

. 147

XYI.

Calliptertjs.

Betularius Betulicola Cai'pini Castanet j Ooryli . I Querceua l^Quercus

14 15 19 26 17 24 21'

BRITISH APHIDES.

V

9

a

LACHNINiE.

Upper wing with twice-forked cu- bitus ; under wing with two oblique veins.

Antennae with 6 joints.

SCHIZONEUEIN^. [

Cubitus once |

forked. Lower •{ wings with two I oblique veins.

r

PeMPHIGINjE.

Cubitus not

forked ; lower wings with one | or two oblique | veins. -\

Cubitus once

forked ; lower wine: with one

oblique vein.

GENERA.

XVII.

Ptekocallis.

fAlni .

< Juglandicola

(.Tilise .

Fagi

XVIII. Phtllaphis.

XIX. C juglandis

Pttchodes. (. &

XX.

Lachntjs.

XXI.

Stomaphis.

XXII.

Paracletus.

XXIII.

Trama.

XXIV.

Dryobius.

XXV.

SCHIZONETJRA.

XXV bis. Cerataphis.

XXVI.

Pemphigus.

XXVII.

Tetraneura. (Aploneura.)* (Toxoptera.)

XXVIII.

TlIELAXES.

XXIX. Glyphina.

f Agilis .

Cupressi

Juniperi

Longipes -{ Macrocephalus

Picege .

Pini .

Pinicolus ^Viminalis

< Quercus

< Cimiciformis

\ Troglodytes .

f Croaticus (_ Roboris

fCorni .

j Fodiens J Fuliginosa "j Lanigera

j Lanuginosa

^Ulini .

< Latania3

fBursarius

Filaginis J Fuscifrons j Lactucarius

Pallidus l^Spirothecae

[ Ulmi .

Vol. IV. Dryophila

f Betulaa . \ Pilosa .

PAGE^

. 31

. 32

. 34

. 37

. 40

. 47

. 46

. 44

. 59

. 48

. 58

. 50

. 52

. 53

. 62

. 67

. 68

74 m

71 l!

107

94

96

89 104

97

197

117

128 113 124 127 122

131

* Vide vol. iii, pp. 135, 136.

GENERAL SYNOPSIS.

r

CHERMESINiE.

Upper wing with j only three veins ; j lower wing with | one oblique vein.

I

Rhizobiin^. Winged forms un- \ known.

GENERA.

XXX.

Chermes.

f Abietis Atratus «j Corticalis j Laricis . l^Pini .

C Punctata

< Quercus Phylloxera. , |^astatrix

XXXI.

XXXII.

Forda.

XXXIII.

Tychea.

XXXIV.

Endies.

XXXV.

Rhizobius.

PAGE

. 24

. 39

. 23

. 33

. 40

. 45

. 49

52,57

( Forinicaria . . 83

(_Viridana . . 85

fEragrostidis . 89

| Phaseoli . . 90

•{ Setaria3 . . 88

| Setulosa . . 87

[_Trivialis . . 86

C Carnosa . . 92

< Formicina . .91

CPellucida . . 91

\ Graminis (Poee) . 93

Genus XXVIII.— THEL AXES, Westwood*

Plattlaus.

Rostrum long, reaching to the third coxse. Second joint very long and thin, third joint thickened, the last pointed. >

Antennae rather short, five-articulate, if the nail-like terminal process be not counted. The third joint equal to the two following, taken together. Cornicles wart-like and very short. Wings carried horizontally, and folded one over the other when at rest. Upper wing with a single furcated cubital vein, the other veins as in Pemphigus. Lower wing has only one single oblique vein, springing from the cubitus.

The eyes in the apterous forms are rudimentary. Kaltenbach points out that they are very small, and that they want the tubercle.

Von Heyden's genus Vacuna has been so generally received by Continental authors that some may feel regret that any change should be made in the name. However, it now seems granted, as a general rule, and in fairness, that priority in descriptions of genera shall decide between rival names.

Prof. Westwood by some years has precedence over Von Heyden, and therefore I adopt his nomenclature as above.

* From 3>jXa£uv, to bear mammae, alluding to the papilliform nec- taries.

O BRITISH APHIDES.

Thelaxes dryophila, West. Plate CXV, figs. 1 — 7.

Vacuna dryophila, Heyd., Kalt., Koch, Pass., Licht.

Aphis dryophila, Ratz., Schr.

Vacuda, Amyot.

Cinara quercus, Sir 0. Moseley.

Apterous viviparous female. Queen Aphis.

Inch. Millimetres.

Size of body O'OOO X 0'055 2-28 X 1*39

Length of antennae 0*035 0*88

Cornicles 0*005 0*12

Oval, flat ; olive-brown, greenish, or chestnut-brown. Rings of the body well marked ; a pale yellowish streak, commencing at the head with diminishing distinctness, passes down the dorsum to the apex ; five dark pore- marks, each surrounded by a pale ring, occur on both sides. Nectaries wart-like, pale, and inconspicuous. Legs and antennaB brown. Eyes very small, and divested of the usual tubercle ; the optical facets, which number only five or six, are set far back on the head. AntennaB about one- third the length of the body ; five-jointed, the third joint much the largest. Body slightly pilose. Rostrum rather short, but this organ is longer in the }^ounger forms.

The queen Aphis or fundatrix is, as usual, much larger than her offspring.

I'h pa.

Inch. Millimetre.

Size 0-060x0-030 1-52x0-76

Small, green or yellowish, with a pinkish hue to- wards the head ; slightly mealy, with two pale streaks

THELAXES DRY0FH1LA. 9

down the sides; sometimes these streaks are broad and dark.

Wing-cases, antennae, and legs pale. Eyes distinct.

Winged viviparous female.

Inch. Millimetres.

Expanse of wings 0*150 3'80

Size of body 0*055 X 0*020 1*39 X 0*50

Antennas 0*025 0*63

Nectaries 0*005 0-12

Head and thorax pitchy brown or shining black. Prothorax paler. Abdomen oval, shining green, more or less mottled. Cornicles brown and very small. Legs green, and of moderate length. "Wings moderate, and folded horizontally ; bronzed and highly iridescent. Their apices rounded. Eyes and ocelli reddish and fully developed.

The colours of this insect are very inconstant. Koch describes and figures two marked varieties, one brown, with yellowish legs, the other with a vermilion- red prothorax and abdomen. The rostrum is long and reaches beyond the first body-ring.

The sexes of this species are minute. They occur late in the year, and are most plentiful during Novem- ber and December. The male is apterous, and about two-thirds the size of the female. Doubtless from its smallness it was long overlooked or disregarded.

Both sexes are distinctly rostrated at their early stages, but possibly they lose these organs at a subse- quent moult, since the Continental specimens are described as mouthless. All the males under my observation have been apterous, like the oviparous females.

Male.

Inch. Millimetre.

Size of body 0-020 X 0*010 0*50 X 0*25 Antennas 0*015 0*38

Oval. Colour lemon-yellow. Antennas sooty grey.

10 BRITISH APHIDES.

Abdomen greenish, with a double row of dorsal spots. Antennae and legs rather long.

Taken in copula with the following.

Ociparous female.

Oval, wholly dingy green, with brownish stains and streaks passing behind the eyes and over the thorax. Abdomen with four rows of brown spots, and seven smaller dots on each side, marking the sites of certain pores other than the stomata, which last are placed on the inferior surface of the body. Legs and antenna short. The abdominal cavity of the specimen described was almost entirely occupied by two large yellow eggs, the safe delivery of which is a mechanical marvel.

Inch.	Millimetre.
Length of body O035 X 0'020	0-88x0-50.
Antennas 0-020	0-50
Cornicles None.

The prevalence of Thelaxes in England is variable both as to quantity and locality. Some years it is very abundant, whilst in other years it is difficult to find. In the late spring of 1871 many twigs and young shoots of Qucrcus sessilij!<>r<i growing round Haslemere were infested by many thousands of larvse crowded round the queen-mother. For several years afterwards I failed to discover any trace of the species on these oaks. In June, 1881, Mr. Foran kindly furnished me with examples taken on Quercus robur near Eastbourne. They were sparsely scattered over the flowers of this oak. The winged form, he told me, was infrequent, but the large queen-Aphides continued throughout July adding to the population of their respective colo- nics. The species is not uncommon in Epping Forest, and at Southgate.

The wings of the parthenogenetio females are often of a rich violet, with a metallic sheen.

The venation is subject to remarkable variations,

THBLAXES PRYOPHILA. 11

the nervures increasing in number and complication so as almost to suggest a dimorphic character. Repre- sentation of these anomalous forms may be seen in Plate CXVII bis, figs. 7, 8.

At Montpellier, Thelaxes would seem to show migra- tory habits, like Phylloxera. In summer the partkeno- genetic forms give rise to the agamous generations on Quercus ilex ; and in December these winged individuals give birth to the sexed insects on Quercus pubescens. In the month of November M. Lichtenstein sent me living examples of the oviparous female; each was burdened with a large egg ready for laying. In no case amongst these could I find that the female had more than one egg, yet there appeared to be no difference between the French and English insects.

In my description of the Genus Callipterus,* notice was taken of Prof. Huxley's memoir on the ' Repro- duction of Aphis. 'f In the former an opinion was stated that the anatomical details ascribed, in that memoir, to Vacima dryophila should be applied to Callipterus quercus. In so expressing myself, it seems to be in- cumbent on me to give reasons, and here I offer the following in substantiation of my views.

As the true males and females of Siplwnopliora pelargonii, the kind previously used for dissection, could not be detected at that time feeding on the ivy-leaved geranium, Prof. Huxley selected a different species of Aphis for his study, and he found an oak in the Zoological Gardens " infested with multitudes of females, full of ova, and also similar ova adhering to the plant in the axils of the leaves, and more particularly between the outer bracts of the buds." In a note Prof. Huxley says that he does not think that his Aphis is identical with that described by Reaumur as feeding on the oak, or that of Bonnet. " None of the specimens attained the size of theirs, neither do they mention the peculiar dorsal marking

* ( Mod. Brit. Aphides,' Ray Society, vol. iii, p. 23, 1881. | 'Trans. Lirm. Soc.,' sxii, 1858.

12 BRITISH APHIDES.

of the newer insects. Also the proboscis of both Reaumur's and Bonnet's Aphides was very long, whilst the others (those under examination) had very short rostra."

Probably Reaumur's insect here alluded to is either Stomaphis quercus or Lachnus longipes ; but their great size, &c, compared with "•£§ of an inch," would exclude them altogether from identity.

The reader is referred to Prof. Huxley's memoir* for a full description, but the same abstracted appears thus :

Size jt£ of inch. Pale green, with four rows of blackish rounded spots ; the spots in the medial line larger than the rest, each spot raised above the integu- ment, and furnished with tufts of long, knobbed, glan- dular hairs. Eyes red, with small tubercles. Antennas about equal to the body, annulated, and seven-jointed ; the proximal half setose. Promuscisf [proboscis] short, extending only to the prothoracic sternum. Abdomen terminated by two rounded anal valves.

The small size, the four rows of rounded spots tufted with capitate setae, the eyes (not " small ") fur- nished with tubercles, the short rostrum, the long seven-jointed antennas, the anal valves, and the numerous true ova, leave no doubt on my mind that these descriptive details belong to Callipterus rather than to Vacuna.

If the winged female had been described in the Memoir, no doubt could have arisen as to the genus and species under dissection. It may be also noted that the minute size of the oviparous female of The- laxes is not so convenient for examination of the internal organs as the larger female of Callipterut quercHs. I believe that, if Gallipterus quercHs be substituted for Vacuna dryophila in the Memoir referred to, the

* Prof, Huxley. "The Agamic Reproduction of Aphis," ' Linn. Trans., L8S8, pi. in. p. 202 ei eeq. '

f Unless this word is derived from the unlikely word promo, it would appear to bayearisenfrom a printer's error for proboscis. As"promuscis" has been eopied by others, I make no alteration, but only a suggestion.

THELAXES DRYOPHILA. 13

value of the observations will remain intact ; and this substitution I would suggest to the author of the paper.

Kaltenbach, in describing the genus Vacuna, states that the winged females seldom make their appearance, and then only late in summer, and that these lay eggs : further he remarks that in this respect Vacuna resembles the genus Phylloxera.*

Again, he says the winged forms appear at the end of August in insignificant numbers, and that then they may be found sitting under the leaves, surrounded by eggs in concentric circles. This is true of Phylloxera quercus, but the fact may be doubted as to Thelaxes (Vacuna) ; at least no winged female Aphis has yet been shown to be truly oviparous.

The galls on the leaves of the oak are occasionally tenanted, not only by Cynipidse, but also by the larvaa of Thelaxes dryophila. These Aphides take no part in forming such " oak-apples "; but they seek shelter and hide in their recesses, chiefly for the large quantity of sap collected in the masses. In Italy Passerinif has noticed the same habit. " Occurrit in quadam galla turbinato-calyciformi quercus," &c.

Aphides have also been observed to nest within certain galls on the evergreen oak, Quercus ilex, near Florence.

Some of the Hemerobiidaa prey on the larvas, and the eggs are greedily devoured by a species of Scymnus. Mr. J. Walker counted upwards of one thousand larvas of Thelaxes under one oak-leaf in the Isle of Man. This large number was reduced to ten individuals within the space of two days through the voracity of one single Scymnus caterpillar.

I here add a few remarks on the general anatomy of Thelaxes dryophila. The alimentary canal is short and

* " In der Forfcpflanzungsweise sckeinen sie der Gattung Phylloxera nake zu steken, mit der sie auck die eigentkumlicke Fliigellage gemein kaken." Kalt., ' Mon. der Pflanzenlause,' p. 177.

f Pass., ' Apkid. Italicae,' p. 83.

14 BRITISH ArHIDES.

but little convoluted in the apterous larva, but in the winged female it is bent into a loop at the lower part of the abdominal cavity before it descends into the rectum.

The viviparous females develop twenty or more embryos, which, at the breeding time, differ greatly in size, according to their maturity. These embryos show red eyes, each compounded of three or four simple lenses. These foetal eyes are quite as large as those borne by the full-grown insects ; thus showing that an arrest of growth as to the eyes occurs during the larval states. It is only after the insect has assumed wings that the complex eye with its ocellus and the stemmata are fully developed.

Behind the three lenses of the apterous female I have more than once discovered a mass of red rods and cones radiating from a centre. These bodies con- stitute the sensitive terminations of the fibres in com- munication with the optic nerve.

The nectaries of the winged female, although very short, have large expanded mouths and long internal tubes, which decrease in diameter, and finally end in transparent ducts. These apparently do not anas- tomose with any viscus, but seem lost in the general fluids of the body. The ducts are directed towards the anal ring ; but whether they have any function analogous to ureters it is not easy at all to decide. Similar ducts may be noted in other genera as well as in Thelaxes.

The reproductive organs of the oviparous female are well suited for dissection. They will be described in the anatomical chapters at the conclusion of this volume.

GLYPH1NA. 15

Genus XXIX.— GLYPHINA, Koch* Kerblaus.

Rostrum shorter than in Thelaxes.

Antennae liv^-jointed, nail-like process somewhat long. Cornicles wart-like. Legs moderate, but very short in the larvaa.

Wings longer, narrower, and more pointed than in Thelaxes. Upper wing with an unforked cubital vein, which does not anastomose with the cubitus. Hind wing with an oblique vein. Stigma long and knife- shaped, f

N.B. — The wing-veining, as in Thelaxes, is liable to variation. In some specimens a very faint tendency to show a forked cubitus may be traced. Koch describes but one species, viz. G. betulce, which, though like the following insect, cannot be identical with it. His figure of Glyphina shows, as above, three simple oblique veins, without any furcation; but Passerini regards this character as abnormal, and not generic.

" Alata prsebit cubitum haud furcatum, quod inter- dum exceptione observatur."| I would suggest that the " exception " is rather the rule. Such a character of venation will also better accord with all other Chermesinas. Under this tribe he places Vacuna, which he considers identical with Thelaxes.

Mr. Monell's new American genus Colopha has much in common with Koch's Glyphina, but neverthe- less the insects must be distinct. The cubital vein only once forked, allies the insect (which some have thought to be identical with Schizoneura compressa of Koch) to Thelaxes ; but the strongly-ringed antennas,

* From y\v<pavov, a surgeon's knife, a scalpel.

t " Messer-formig," Koch, p. 259.

X Passerini, ' Aphididae Italica?,' p. 83.

16 BRITISH APHIDES.

the form of the wings, and the clouded inner margin of the stigmata, show some accord with Grlyphina.

Glyphina pilosa, Buckton. Plate CXVI, figs. 1 — 4. Apterous female.

Inch. Millimetre.

Size of body 0-070 X 0'040 177 X l'Ol.

Length of antennae 0*040 l'Ol.

Body oval, globose. Dark olive-green or blackish, pilose, and flecked with white down, which is most plentiful on the apical rings. Eyes dark brown. Cornicles black, and inconspicuous. Legs stout, pale olive-green, tarsi long, rostrum rather short. The down on this insect is pale greenish.

Numerous during some seasons at Haslemere, on the Scotch fir, throughout the months of July and September. Mr. Walker sent me specimens feeding on Pinus sylvestris at Southgate, all of which in the alate forms showed the non-furcated cubitus. He supposed the insect to be Lachnus pineti, Kalt., which, however, has distinctly a double furcation in the upper wing.

Winged viviparous female.

	Inch.	Millimetres.
Expanse of wings	0-229	5-74.
Size of body	0-070x0-035	1-77x0-81
Length of antennas	0-030	0-76.

Body rather linear. Head and thorax dark brown and shining. Abdomen smooth, carinated, oval, greyish drab. Hind legs long. Wings long and narrow, fuscous, and somewhat wrinkled, dull. Insertions, cubitus, and stigma pale greenish. The other veins are pale ochreous and usually very indis- tinct. The third or cubital vein unforked, and often it does not anastomose to the cubitus. Stigmatic vein

GLYPHINA BETUL^. 17

straight, and leaves the stigma at about an angle of 45°. Stigma long and pointed.

Koch has described an insect under a new genus, Mindaurus or Mindarus, which has some characters in common with Glypliina pilosa, but this last Aphis, nevertheless, does not agree with his Mindarus abietinus, notwithstanding their similar habitats.

Glyphina betul-s:, Heyd. Plate CXVII, figs. 1 — 5.

Vacuna betulce Heyd., Kalt., Ratz.

,, alni, Pass. (?) Tlielaoces betulce, Walk. Glypliina betulce, Koch. Tremulinax, Amyot.

Apterous viviparous female.

Inch. Millimetres.

Size of body 0*090 X 0*040 2*28 X 1*01

Length of antennae 0*015 0*38

Oval, flat, dark green, with a pale dorsal streak, and a row of disjointed white spots down the sides. Antennae very short and partially developed. Rostrum and legs short.

Pupa smaller than larva, with rounded head, large eyes, and longer legs.

Winged viviparous female.

Inch. Millimetres.

Expanse of wings 0*240 6-09

Size of body 0*090 X 0*030 2*28 X 0*76

Length of antennas 0030 0*76

Body long-oval ; head round ; antennae short, third joint the longest. The fourth, fifth, and sixth joints about equal. All joints are deeply ringed. Thorax brownish. Abdomen olive-green. Legs moderately

vol. iv. 2

18 BRITISH APHIDES.

long, yellow-green. Wings long, very hyaline, with pale-yellow veins and greenish stigmata. These have darker inner margins. Cubital vein without any fork. It does not anastomose with the cubitus, but is cut short as in Schizoneura. Third and fourth veins proceed almost from the same point of the cubitus. Lower wing with a single faint oblique vein.

The ringed antenna! joints are not noted by Koch, but Kaltenbach describes Vacuna as always annu- lated in these organs, " alle zart geringelt," and gives a rough figure in accordance with this character.

Passerini considers Vacuna betulce to be identical with V. alni, which, in Italy, infests the ends of the branches of Alnus incanus.

Thelaxes betulce is noted by "Walker in his * Cat. of Hemipt.,' vol. iv, p. 1052. Elsewhere he says, " it is sometimes common in the Isle of Man."

IV. CHEEMESIN^B, Pass.

UPPER WING WITH THREE OBLIQUE NON-FURCATED

• VEINS. UNDER WING WITH A SINGLE OBLIQUE YEIN.

CHERMESINjE.

This tribe is limited as to species, but it contains several insects of interest. The simple character of their wings separates them from the foregoing Aphides, and brings them nearer to the Coccidas, to which also the larvse approximate in form, and somewhat also in habit.

Some kinds are bark-feeders, some are gall-makers, some inhabit tufts of woolly matter spun from their bodies for concealment, and others, like Phylloxera, have aerial and subterranean habits combined in the same individual.

Genus XXX.— CHERMES, Linn.*

Tannenlaus.

Rostrum very short and stout. The setae prolonged sometimes twice or thrice the length of the whole insect.

Antennae short, stout, five-jointed, and terminated by a minute button usually furnished with bristles. The third, fourth, and fifth joints nearly equal. The first and second shorter.

Cornicles wanting.

Head and prothorax disproportionately developed. Fore wings broad. Costa rounded. Cubitus stout and terminated by a broad stigma, which by encroach- ment on the cubital cell shows some approximation to the semi-coriacous texture of the Hemiptera Hete- roptera. The fore wing has one stigmatic and two simple non-furcated oblique veins. The hind wings have a single oblique vein. The oblique veins of the upper wing sometimes do not anastomose with the cubitus, but spring from a continuation of the stig- matic vein, which runs for a certain distance parallel to and below the cubitus.

This characteristic led Koch to divide Chermes, and to describe the insects having this last peculiarity under a new genus Anisophleba ; but I have hesitated thus to split up the genus, for I am not clear that this con- formation is constant in any species.

The males of Chermes have been slightly noted by Kaltenbach, Ratzeburg, and Koch, and described as

* Chermes or Kermes, probably from the Arabic or Hebrew Tp"]j?.

22 BRITISH APHIDES.

winged ; but anatomical evidence that the insects in question were of this sex is desirable.

The apterous male I have discovered in Chermes abietis, and this sex I have clearly proved by dissec- tion.

Passerini's* remarks on the propriety of retaining the genus Chermes amongst the Aphididas appear to be judicious. It is true that the tribe as now restricted does not fully accord with the characters originally set forth by Linnaeus, nevertheless some confusion would now arise by a transfer of the name to Coccus, as has been proposed by Geoffrey, and afterwards carried out by Vallot in his genus Adelges. As regard should be paid to priority, I follow Kaltenbach, Koch, and many other authors in retaining the name of Chermes amongst the Aphididae.

The ancient Persians seem first to have given this name, Kermes, to the red dye obtained from the insect, called afterwards by Linnaeus Kermes ilicis (now Coccus ilicis). The red produced from Kermes is not of such a vivid scarlet as that yielded by Coccus cacti, the cochineal scale-bug.

The name, Kermes mineral, given by the old chemists to one of the ores of antimony, a substance used in the East to dye the eyelids, probably has the same etymo- logical source. The Moors have left a similar word, Kermez, in Spanish, for a dye.

Though the galls commonly found on the English oaks are not the work of an Aphis, we may conceive that this insect was called upon to act a part in the adjuration so playfully set forth by Mr. Tennyson in tho soliloquy of the talking oak of Sumner Chase : —

" I swear ! and else may insects prick Each leaf into a gall."

* Passerini, ' Flora degli Afidao Italiani,' p. 3.

OHERMES CORTICALIS. 23

Cheemes cortioalis, Kalt. Plates CXVII, figs. 6 — 10;

CXVII, bis, figs. 1—3.

Chermes strobi, Hartig (?). ,, piceo3 (?), Ratz.

Apterous female.

Inch. Millimetre.

Size of body 0-035x0-025 0-88x0-62

Length, of antennas 0*005 0*12

Small, ovate, ochreous brown. Head dark umber- brown. Abdomen covered with minute tubercles, from whicli is extruded a quantity of flocculent silky fibre, within which, mixed with mealy matter, the Chermes conceals itself. When denuded of this cover- ing the insect shows numerous dots of deep brown, disposed in rows down the dorsum. Legs very short. Eyes exceedingly small. Antennas brown, and mostly hidden. The rostrum short, witli long flexible setas.

Pupa.

Oblong. Head and prothorax rich brown, as also are the wing-cases, antennas, and legs. The abdomen is transversely barred with brown.

Winged viviparous female.

Inch. Millimetres.

Expanse of wings 0-150 3*80

Size of body 0-040 X 0*025 1-01 X 0*63

Lengtli of antennas 0'013 0*33

Larger than the larva. Black ; head broad ; eyes conspicuous ; antennas black and five-jointed, each articulation furnished with a strong bristle. Thorax capacious, black and shining. Abdomen ringed and furnished with flocks of white silky thread. Legs black. Tarsi furnished with sucking discs as well as claws. Wings fuscous, punctured, dull, and

24 BRITISH APHIDES.

parchment-like. Veins brown and coarse. Stigma broad. Rostrum short. In my figure, the veining of one fore-wing is drawn as abnormal ; a circumstance not infrequently seen amongst these low types.

Sometimes this Chermes is very numerous on the twigs of the Scotch fir, Pinus sylvestris. In early June they form numerous tufts of white cotton round about the bases of the green needle-like leaves. If these tufts are searched, the apterous mother may be seen surrounded by thirty or more yellow eggs, which become browner as they attain maturity. The ova are much preyed upon by larva? of Scymnus diseoideus, Anthocoris fusca (Kalt.), Agromyza ehermi- vora (Kalt.), and other ravenous insects.

Kaltenbach originally took this insect plentifully on the Weymouth pine (Weikmuthskiefer), Finns strobus. He gives a figure of the wing showing the peculiarity of veining which belongs to Koch's genus Anisophleba.

Chermes abietis, Linn. Plates CXVI, fig. 5 ; Plates

CXVIII and CXIX, figs. 1—2.

Chermes abietis, Linn., Fab., Schr., Kirby and

Spence, Kalt., Koch, Pass., Eatz., Leuckart.

Adelges gallarum abietis, Haliday. ,, ah i ctis, Walk.

Aphis gallarum abietis, De Geer, Burm.

Sacchiphantes abietis, " Ruricola."

Elatiptus, Amyot.

Apterous viviparous female. Queen-Aphis ?

Inch. Millimetre.

Size of body 0'035 X 0*022 0-88 X 0*55

Length of antenna) 0'009 0'22

Very small. Blind. Ochreous yellow. Mealy. Oval ; mite-like in form ; dorsal portion domed.

CHEEMES ABIETIS. 25

Legs short and greenish. Rostrum short, but fur- nished with long setae.

Early in April ; as soon, indeed, as the shoots of the spruce begin to push forth, the foundress commences her operations at the axils of the young leaves. A small swelling here makes its appearaDce, within which she encircles herself. This swelling occasionally attains the size of a hazel-nut ; and sometimes it grows very much larger.

In the month of May she may be found surrounded with numerous larvae, larger than herself, all of which develop rudiments of wing-cases. It would appear that, with the exception of the above queen- Aphis, all individuals become alate.

The cautious and indefatigable naturalist De Geer was the first to give a full history of Chermes abietis. Observers who came after him have only amplified and very generally confirmed his discoveries. " In early summer the shoots of the spruce-fir may often be seen covered with excrescences, which are so similar to true fir-cones that they readily deceive the casual observer as to their true nature." De Geer proved that these are produced by the punctures of an insect, exactly as we have seen the galls produced by Tetra- neura and the like.

The queen Chermes or Altmiitter certainly hyber- nates ; and it is clear that she only wakes upon the return of spring, just as the sap begins to rise into the buds. By absorption she soon passes out of her shrivelled dry condition into plumpness, and then she lays one or more heaps of eggs in the neighbourhood of a bud, which she selects at the axils of two or more succulent branches.

The punctures she continues to make at the base of this bud cause an arrest of its usual growth, and by a diversion of the sap a thickening and swelling at the bases of the needle-like leaves are produced, which eventually take the form of numerous cells, the aper- tures of which gradually approximate to each other.

26 BRITISH APHIDES.

It is not yet quite clear if the queen-mother dies outside of the developing gall ; leaving thus the young which hatch from her eggs to enter these chambers alone ; or whether she accompanies them into their retreat. De Geer says that while the formation of the gall proceeds, the old pine-louse dies (he does not say where) of her infirmity, " die alte Tannenlaus aus Entkriiftung stirbt."

On the other hand, I have commonly found a wing- less Chermes surrounded with young pupa?, and quite enclosed by the walls of the chambered cone.

This insect I consider to be the original queen- Aphis; and if she be such, the encystment would be in perfect accordance with the nidification of the females of Pemphigus, Tetraneura, and the like. On the other hand, this hatching outside the gall is in accordance with Miss Ormerod's observations,* who remarks, in her useful Manual, " with regard to the larva? that were hatched outside presently becoming tenants of the inside of the gall there is no doubt, . . . but I believe that a minute slit opens along the upper part of the sutures that mark the division of the swollen leaves, and that through these openings the larva? creep into the chambers within."

By the irritation of the larva? the cells increase in size, and finally become large enough to contain from twenty to fifty insects in each chamber; their rostra being plunged into the substance of the cell, and all their heads being turned outwards and towards the opening ; that is, the larva? all radiate from the centre of the cone. As before noted, the queen Chermes may be found within, surrounded by her progeny, which, niter undergoing several moultings of skin, develop their wing-cases. Eventually all, without exception, become pupa?.

A quantity of mealy matter lines these chambers ;

* E. A. Ormerod, 'Manual of Injurious Insects,' p. 242. I tliink fm-tber observation is desirable as to tbis question of encystment. — G. B. B.

CHERMES ABIETIS. 27

and numerous pellucid globules may be found inter- spersed, which I regard as fascal matter.*

Although these insects are too closely packed together to allow of any locomotion, they walk readily after removal from their nidus. Fine black bristles protrude from the points of their rostra, by which they hold firmly to the inside of the chamber.

As a cone may have fifty or more inhabitants in each separate chamber, a single structure, even at a moderate computation, may contain two thousand inhabitants. A section of one of these pseudo-galls often shows the spruce shoot as an axis around which the various cells are symmetrically placed.

Shortly after the middle of June the scales contract and open, so as to form clear exits for the pupas. These on a sunny day will emerge by hundreds and mount on the spines to dry their expanding wings. A gleam of bright sunshine will call them forth in clouds ; each insect taking wing with a whirling motion, and a " buzz " very loud for a body so small. After the escape of the Chermes the cones dry up and form hard masses of open cells, which remain long afterwards on the trees.

I have in vain searched for winged males amongst the thousand forms I have bred under bell-glasses during different seasons. Leuckart, indeed, some years ago denied the existence of any male ; but after the recent interesting discoveries on the dissimilar genera of Neuroterus and Spathegaster by Dr. Adler, and the remarks by M. Lichtenstein upon the Cynipidce, it will be hazardous now to commit oneself to such an opinion.

Ratzeburg believed that he had discovered the

* This mealy matter is insoluble in alcohol, but it dissolves in benzole. It is composed of an abundance of broken and flattened threads, which polarise light. Doubtless these are minute portions of the corkscrew- like, silky masses, which are secreted by certain glands, and which are pressed through certain apertures to be seen on the body-rings, by em- ploying a microscope with a suitable amplifying power. This mealy matter, and the corresponding secreting glands, are figured in Plate C, vol. i, figs. 6, 7, 8, and 9.

28 BRITISH APHIDES.

winged male, and he figures this insect in his ' Forst- Ins.,' iii, 200. He says that he repeatedly saw the male organs, which can be made to protrude by a gentle pressure of the fingers. I doubt much as to the fact of this insect being a male ; and the more so, as a similar pressure will cause the protrusion of a short and blunt ovipositor from the winged females produced from the pseudo-galls. The same may be stated with reference to the winged female of Chermes laricis, the allied species, the male of which is at present quite unknown.

The winged females, after finding suitable localities, permanently attach themselves to the spruce leaves, lay their eggs, and die ; their dead bodies becoming protective covers for their young broods, which hatch under them and emerge in early autumn. These young spread themselves over the twigs, but have not been observed to make fresh cones. Apparently they hide themselves under the stipules of the leaves in a manner similar to that of the larch Chermes. Do they there hybernate ? or, if not, what is their economy ? and what is the part they play in the cycle of life during the remainder of the autumn ? These questions yet call for an answer ; but at present conjecture only can be advanced.

Inch. Millimetres.

This measures 0"090 x 0*050 2'28 X 126.

Colour warm reddish-brown, with a delicate bloom upon it. Head broad, eyes brown ; thorax and pro- thorax remarkably broad and massive. Abdomen deeply ringed. Apical ring furnished with a small cauda and two minute spines. Legs very short. Wing- cases and thoracic lobes greenish. The whole under- side of the pupa has a rich ferruginous, but dull and milky tint. Some specimens are more slaty-grey than others.

CHERMES ABIETIS. 29

The pseudovarian sacs are very numerous in the pupge of Ch. abietis. The small anterior chambers of the pseudovaria are filled with a green granular matter; whilst the larger posterior chambers show well-marked indications of the ova, which nevertheless cannot get their full development until the imago has emerged from the pupa. The exuviae of the pupa are quite white, and perfect as an investing shell, just as we see in Aphis proper.

The cavities of the bodies of these Chermesinse are filled with minute, green, nutritive granules, which pass into their hollow legs, and these globules show their freedom by their change of position at each moment that a contraction is made by the insect. The pulsa- tion of the dorsal vessel also may be readily seen, if the winged insect be immersed alive in weak glycerine, under which solution it will survive with a diminished activity for some hours.

Winged female.

Inch. Millimetres.

Expanse of wings 0*270 6*85.

Size of body 0090x0-045 2-28xM3.

Antennas 0*020 0'507.

Cornicles None.

Vertex flat. Head broad; eyes brown. Antennas short, 5-jointed; last three joints imbricated. Pro- thorax dilated to the full width of the body and marked, by a somewhat triangular lobe. Mesothorax with two large and two smaller lobes. Post-thorax long and narrow. Abdomen oval, very shining, and sparsely clothed with waxy filaments. Cauda not visible ; but two prehensile hooks and a short ovipositor can be extended at the will of the insect. The whole insect is of a fine golden-brown colour, which deepens by age. Legs green and very short.

"Wings broad and somewhat pointed; when first

30 BRITISH APHIDES.

disclosed they are of a milky white, but they speedily become hyaline, with a delicate greenish glance. Cubitus green and stout, the apex expanding into a large green stigma. The three oblique veins usually stop short of the cubitus. Lower wings with a single vein proceeding at right angles from the post-cubital. The membranes are finely punctured. The wings are folded horizontally ; that is to say, not pentwise.

This insect is numerous in many English counties. It also has a wide Continental distribution, reaching as far south as Parma, in Italy.

The winged Chermes begins plentifully to issue from the cones in early June, and if the season be late, they continue their flight even to August.

They may be found, later in the year, sitting at the apices of the leaves in the process of oviposition ; the eggs being afterwards covered by flocks of woolly matter. Still later in the year the young may be discovered creeping from the dead body of the mother ; her body having answered, for the time, for their temporary concealment.

The later-born winged females are only half the size of the ordinary insect, they are browner or greener than those of the early summer, and their abdomens are less developed. These probably are the supposed winged males, described by Koch. It is more possible that they develop the real sexes; and the mothers thus would be styled pupiferce by Lichtenstein. I think this the more likely, since their abdomens are largely charged by green germinal matter, and when they are crushed a multitude of minute spore-like bodies are liberated, which simulate spermatozoa.

In the family of Aphides the organs destined for reproduction commence their growth at a very early stage. The rudiments may be sometimes traced in the young of Chermes abietis soon after their exclusion from the egg. It is well known that the sexual appa- ratus is in formation some time before the construction of the principal external parts of the Aphis. The

CHERMES ABIETIS. 31

occurrence of germinal matter in these imagos, there- fore, need cause no particular surprise.

Here it may be mentioned that a splendid magenta- coloured dye is produced by the action of dilute potash. The reaction is marked under the microscope. An excess of potash injures the colour. The ovoid masses in the abdomen become, under the same reagent, differently tinted ; one half changes to a deep purple, whilst the other half remains yellow or green.

Circumstances unfortunately prevented a minute examination as to the sexes of the insects bred from under the bodies of these winged females. As before hinted, they might have proved to be males and true females ; but, assuming this, their birth would seem to occur both externally and internally, as to the pseudo-cones. But there is yet another supposition, founded on analogy with Ghermes laricis, in which the commencers of the next year's colonies undoubtedly hybernate. Here, under the idea that the progeny of the winged Chermes is non-sexual, the male influence would be deferred until the end of the cycle, and the true ova might not be produced at every autumn.

I have depicted at fig. 6, Plate CXVTII, one of these small winged insects, with her progeny.

I cannot certainly say that they always and exclu- sively breed outside of the cones. I am in the greater doubt, since my discovery, within the cones, of the wingless male, as if it had been bred there.

Apterous Male.

Through the kindness of Miss Ormerod, late in July I had the opportunity of searching the contents of a number of pseudo-cones, and, after a long trial, I detected, just under a scale, a single minute apterous insect, which proved to be the sex long missing. This specimen measured only 0'030x 0*015 of a millimetre.

Exceedingly minute, yellow, blind, apterous. An-

32 BRITISH APHIDES.

tennce rudimentary and composed of three joints only. Rostrum very short. Head broad, and joined to the body without the intervention of any well-marked thorax. Abdomen large and deeply ringed. The posterior end is occupied by a remarkably developed male apparatus, which by compression under weak glycerine gives rise to a plentiful stream of sperma- tozoa. The alimentary canal is very short, and the nutritive organs are very simple. The cavity of the abdomen is taken up almost entirely by the sperm- capsules; but I am unable to satisfy myself as to the correct number of these last united into a single duct.

Several other small, wingless Chermes were dispersed within the cells of the pseudo-galls, but I could not be sure of their sex. Inasmuch as they contained no visible ova, they might have been immature males. It is likely that one male visits many cells in succes- sion, and thus the smaller sexed females, if bred within the cones, would be fitted for their subsequent ovipo- sitorial duties.

The above description affords yet another example of the apparent rule that a recurrence to a fecundated ovum is the ultimate step taken before the pheno- menon of a true fresh birth. Thus, as the males have at last been found in Coccus and in Cynips, so now Chermes offers no exception. The degraded characters and minuteness of this sex have been the chief causes of their being overlooked hitherto.

It will be noted that in all the true Aphides hitherto described the oviparous females are wingless, and pro- bably will always be found to be such.

There is, however, a departure in Chermes from Aphis proper. The queen Aphis in Pemphigus, Schizo- neura, Tetraneura, &c, is the constructor of the gall she inhabits. She surrounds herself with vegetable growth, and in the cavity which she produces she stores her young, and their pricking increases the size of the gall already formed.

In Chermes ahietis we see, according to the observers

CHERMES LARICIS. 33

above quoted, that the excrescence develops itself solely by the punctation or boring into the swelling bud by the mother Aphis, long before the eggs she lays are hatched. After this has taken place the mother louse "dies of infirmity," but in the meantime the little insects slip out of the eggs, and immediately betake themselves to the juicy galls which have been caused by the mother. They crawl into the corners of the closely compressed and scale-formed needles, and try to penetrate between them.*

Miss Ormerod, in her useful ' Manual of Injurious Insects,' gives much the same account, and would seem to have witnessed the entry of these young Chermes into the chambers from without. She says the larvae spread themselves along the lines which divide the galls, " apparently . . . disappearing into the chambers within." f

Through the kindness of friends I have received pseudo-cones from Norwich, Bishopstoke, Isleworth, Bramshot, Arlesford, and other places.

I believe that Chermes viridis, Ratz., is only a variety of C. abietis.

Chermes laricis, Hartig. Plate CXIX, figs. 3 — 9 ; Plate CXX, figs. 1—4.

Eriosoma laricis, Sir Oswald Mosley. Chermes laricis, Kalt., Ratz., Koch.

„ geniculatus, Ratz. Anisophleba hamadryas, Koch (?). Adelges laricis, Vallot.

Queen Aphis.

Inch. Millimetres.

Size of body 0-070 xO'045 l'77xl'14

Length of antennae 0-015 0*38

* Kaltenbach, ' Monographic der Pflanzenlau.se,' p. 202. t E. A. Ormerod, ' Manual,' p. 242. VOL. IV. 3

34 mUTISTT APITTDES.

Body broad and scutiform. Head, thorax, and abdomen obscurely divided. Colour blackish-brown. Six rows of tubercles disposed down the back and carina. Dusted with mealy or flocculent matter, which is most abundant towards the tail. Antenna very small and partly hidden, composed of three to four joints. Legs very short, hardly protruded beyond the circumference of the body. Tarsi with two claws. Tail furnished with two hooks. Rostrum rises between the first pair of coxae.

Habit very inactive ; the insect probably never leaving the spot at which oviposition has commenced.

This insect is plentiful on the larch (Pin us la fix), and sometimes occurs in sufficient numbers to materially injure the trees. In the year 1871, from May to October, the woods in some parts of Surrey were so covered with the myriads of white tufts spun from these insects that they appeared as if starch had been dusted over them. Many boughs died back, and in the autumn the trees looked as if they had been scorched.

For a long time I was unable to satisfy myself as to wh ether it were a fact that the queen Aphis hyber- natcd, or was born from eggs surviving the winter. In 1872 I watched continually for the first appear- ance of this Chermes. It was not till the 27th of February, when a slight increase commenced in the tree buds, that I was able to detect, under a high magnifying power, several batches of from eight to ten individuals secreted under the leaf-scales, which were commencing to rise. These insects were so shrivelled and dry that no one would suppose them capable of waking into activity. They were very small, and entirely of the colour of the larch bark. As the sun warmed the air and the sap rose, the Aphides began to swell from inhibition of moisture, and then threw off their skins by a peculiar vermicular motion, the rejected Blough" passing slowly towards the tail.

For several days the fresh moulted Chermes retains this skin, which is attached by three long, spirally-

CHERMES LARECIS. 35

coiled liairs, which, may be traced from the tip of the rostrum of the living insect to the tip of the inverted and discarded sheath. These, in fact, are the three setae found in the oral sheaths of all Aphides.

The growth of these setae, which uncoiled may be three times the length of the insect itself, is not at all obvious. It is well known that the legs and antennae of Aphides are extricated from their old coverings, even to the last joints, without fracture of the " casts," but in the above case the skin of the rostrum must be turned inside out like the horn of a snail to permit of the continued attachment of the insect to its exuviae.

The extreme tenuity of these setae would make it seem almost impossible that there could be an eversion ; but Prof. Allman has shown that the still finer urti- cating filaments of some Hydroids are similarly ex- serted, and so rapidly, that the eye quite fails to follow the action.

I look upon these curious coiled hairs as spring cables to secure the insect from being dislocated from the branches by the rough winds of March. The slough fixed in the bark-crevice acts thus as an anchor. The insects can hardly be removed by friction with a hair pencil.

By the 4th of March, the queen Aphides, having considerably grown, again shed their skins ; and then they appear of a silvery white spotted with pale brown tubercles. They soon change to a green colour. Two days after another moult is effected, and then I saw six eggs laid whilst under the micro- scope. By the 9th of March twenty-four eggs were laid, the mother not having moved from her first position on a young twig.

At the moment of oviposition a short and cleft ovipositor is exserted, but I failed in discovering how the eggs are attached to their long pedicles. But the process very likely is similar to that performed by Hemerobius.

3G BRITISH APHIDES.

These egg-tufts contain from thirty to sixty ova, and are of all shades of colour, according to their ages ; from yellow to dark brown, ferruginous, and black. Subsequently the ova are covered by a peculiar silky substance, the packing and disposal of which are effected by means of the cleft ovipositor before noted.

The Altmutter, or queen, broods upon these eggs, which hatch about the end of May, about which time the green tufts of larch become dotted with small black grains like gunpowder. These are the produce of the queen Aphis's eggs.

The larvas measure about 0*020 XO'010 of an inch, or 0'50x0'25 millimetre. They are green, slaty-grey, or black ; and are very unlike their parent. They are longer, with head and thorax more separated from the abdomen. The body-rings are more marked, and the six rows of tubercles are more apparent.

A resinous-looking fluid is secreted, which exudes like small yellow drops from their tail ends. This juice is an object of interest to ants and to wasps. The latter insects, in June and July, keep up a continual hum during their visits to the larch trees. The young Chermes soon double their size, and puncture the needle-like leaves so as to produce a sort of weeping of turpentine, and to cause the leaves to bend at a sharp angle where the injury has taken place.

The Chermes also shroud themselves in the silky matter which, from the odour it gives when burnt, seems to be of a nitrogenous nature; and appears to be capable of flattening by pressure, and even unravelling into smaller fibres or filamentous threads. It is in- soluble in alcohol, and it does not seem to be of a waxy nature.

The tarsi of the insect are furnished with two stiff hairs, ending with discs, which probably act like pul villi. Those black tuberculated larvaD, after under- going certain moults, develop their wing-cases, become pupa3, and finally emerge as imagos.

CflERMES LARICIS. 37

Pupa.

Dark-grey or slate-colour. Body covered with warty tubercles, which form orifices from which the silky matter is spun. Head and thorax much produced forward. Wing-cases placed far down in the meso- thorax. Antennae relatively rather long.

The pupae are pretty plentiful at the end of May, and the imagos appear in early June up to August. I have never, however, observed the winged Chermes in anything like the abundance of the pupae ; but this may be easily accounted for by their easy destruction through rain, and also by the power of the wind to remove them far from their birthplaces. Aphides have no power to breast a strong wind ; their wings act only as organs of suspension, and thus they have but little directive force.

Winged female.

Inch. Millimetres.

Expanse of wings 0*180 4"57

Size of body 0'055 X 0'020 1*39 X 0'50

Antennse 0*010 0'25

Head and thorax dark-brown ; eyes red and large. Antennae about equal to the width of the head, the third, fourth, and fifth joints irregularly ringed and imbricated ; terminal button bristly. Prothorax very large and unweildy; meso- and post-thorax support- ing the wings, less developed. Abdomen orange or brown, much ringed, and plentifully furnished with wavy silk fibres. Legs brown, and moderate in length. Wings large, broad, greenish, and finely punctured. Cubitus and stigma pale olive-green, tipper wings with three simple unforked veins, the last of which usually is the only one which springs from the cubitus.

It may be a question whether the apparently parallel course of the stigmatic vein below the cubitus is due to more than the abnormal expansion of the cubitus

38 MUTISH APHIDES.

itself. As before noted, however, Koch thought this a character sufficiently marked to justify his genus Ani- sophleba. The under wings have but one oblique vein.

A gentle pressure on the abdomen causes the insect to exsert the prehensile hooks, which I believe Ratze- burg mistook for a penis, and thus he looked on certain slightly different alate insects as the males of Chcrmes la/ricis.

These winged females, after finding a suitable spot for oviposition, exclude their eggs in considerable numbers, clothe them with the down from their bodies, and then die. Their dry skins, with the wings at- tached, form, as in the last species, a certain protec- tion over the eg^gs. Throughout all the summer apterous and winged females may be seen ovipositing side by side until the succulency of the sap is too much reduced to give nourishment.

The males and true females of CJtennes Jar ids are yet to be discovered, and inquiry is yet desirable as to the fact whether the last be apterous or winged ; but I believe that the true egg is laid by an apterous insect and hatched in autumn. Without such a habit we cannot explaiu the hybernation of the queen mother.

I hesitate to adopt Koch's observation that the smaller winged insects which appear simultaneously with the apterous are real males and females. The former, under his view, might have been males ; but it has not yet been demonstrated that any real females among the Aphidina3 are otherwise than apterous.*

The hybernation of Chermes is a fact. I have dis- covered the insect secreted in the bark-fissures, near the incipient leaf-buds, as late as December 12th and as early as February 27th. At the former date I could find no evidence of enclosed eggs, or rather they were limited to mere rudiments.

The alimentary canal was easily traced, and there were several blind sacs visible within the posterior rings, which in all probability were the colleterial glands.

* Koch, ' Die Pllauzculiiuse,' p. 317.

CHERMES ATRATUS. 39

Kaltenbach infers that the eo*gs are laid in the autumn, and protected by the silky matter.* I have made unavailing search for such eggs in February. But few traces of cotton-like tufts can then be found, and I have uniformly found them empty.

Ratzeburg at one time thought that two species of Chermes infested the larch ; one of which he named Chermes geniculate, from the stoutness of the knee- joints. Subsequently he believed this to be only a variety, and he discarded the supposed species accord- ingly.

Passerini has not included C. laricis amongst the Aphides of Italy. The insect is confined to Plnus lariv, and probably it is only to be met with where that tree is indigenous, or where it has been introduced artificially.

Chermes atratus, Buckton. Plate OXX, figs. 5, 6. Winged female.

Inch. Millimetres.

Expanse 0*180 4*57

Size of body 0*045 X 0*025 1*14x0*63

Length of antennas 0*010 0*25

Whole body sooty grey. Head broad ; eyes black and prominent ; prothorax largely developed, with broad lateral swellings ; mesothorax large, with pro- minent lobes, from which the voluminous, greyish, and finely punctured wings spring ; post-thorax moderate in size. Abdomen blunt, fusiform, marked with three or more dark crescentic bands. The head and thorax occupy more than half the length of the whole body. Abdomen sparsely clothed with long white filaments. "Wings grey and dull. Cubitus and insertions dull yellow. Stigma long and dark sooty grey. Antennas with two large basal joints, followed by three other joints, all much imbricated, and

* Kalt., ' Monogr.,' p. 195.

40 BRITISH APHIDES.

dilated at their inner aspects into three drum-like tubercles (auditory?). Legs short and black.

This somewhat singular-looking insect was taken on an oak at Haslemere early in June. I could find no apterous females in the vicinity; and therefore very probably the fly was not bred on that tree, but had strayed from its birthplace.

As it answers to no published description of a Chermes, and yet has some marked characters, I add it to the list of British insects, with the anticipa- tion that the immature forms and the life-history will at no long time hence come under notice.

The following short list comprises, I believe, all the species of Chermes as yet described from European localities :

Chermes abietis, Linn.; Ch. laricis, Hartig; Ch. corticalis, Kalt. ; Ch. strobilobius, Kalt. ; Ch. pini, Koch ; Ch. coccineus, Ratz. ; Ch. atratus, Buckton ; Anisophleba hamadrias, Koch.

It is to be noted that the larval forms of Chermes seem to approach nearer to those of Coccus ; and that in their alate forms the costaa of the wings and the dilation of their stigmata (coupled with the tendency shown by some to deposit chitine in the ordinary substance of the membrane) suggest some possible passage out of the Homoptera into the lower members of the Heteroptera.

Chermes pini, Koch (?). Plate CXVII bis, figs. 4— G. Anisophleba pini, Koch.

Apterous oviparous female.

Inch. Millimetres.

Size of body O035 X 0*022 0*88 X 0'55

Length of antenna 0'005 0*12

CHEUMES PlNt. 41

Coccus-like in form. Dark - brown, plentifully furnished with long silky filaments, which take a corkscrew form as they issue from the body-pores. When denuded, the insect shows the body deeply ringed, and marked with spots of varying size down the back and the sides. The antennaB are very small, and they are usually inconspicuously folded under the head. They are very rudimentary in form, and only contain from three to four joints. The queen Aphis occurs in May, and about June is surrounded with her pedunculated eggs, which are yellow or brown, and well covered from the weather by cottony flocks.

In 1874 they were taken plentifully at Haslemere on Pinus sylvestris, and in December of the same year, when the thermometer marked 21° Fakr., the apterous mothers were found congregated in knots of from ten to fifteen at the bases of the leaf-tufts of Pinus insignis. They were then very inactive, and usually attended by the grub of a Scymnus, which daily devoured some of them, leaving comparatively few to pass the winter. Like other Ohermes, they were anchored to the buds by long rostral setae, more than twice the length of the insects themselves.

Koch found, at the Botanical Gardens at Erlangen, a Chermes which, from the character of the wing- veining, he put into a new genus. He called this insect Anisophleba pini. They were first noticed in the greenhouses on a variety of the Scotch fir called Pinus siberica, but the insects spread beyond the greenhouses to other species of Pinus, amongst which he names Pinus uliginosa.

In a general manner his description agrees with that above given; but his specimens seem to have been brighter in colour, and the legs were ringed with yellow near the femoral joints.

I have not been able to secure the winged form of Chermes pini ; but Koch says that his pupae had large and smooth thoracic lobes, with olive-brown wing cases.

42 BRITISH APHIDES.

The winged females are, he remarks, very similar to those of Anisojphleba hamadyas (Chermes laricis ?), but they want the tubercles which stud the body. Again he remarks that this insect has a close affinity to Chermes corticalis of Kaltenbach, which insect is not, however, included in the list given by Koch.

It is to be regretted that the illustrations of Chermes in Koch's ' Pflanzenlause ' are far from satis- factory. They give but little help in identifying the species he describes.

Kaltenbach adds to his list of Chermes Gh. strobi- lobius, which has not yet been noticed in England. It forms a yellow pegtop-shaped gall (Zapfenartigen) swelling towards the ends of the twigs of Pinus abies.

Genus XXXI.— PHYLLOXERA,* Boyer de Fonsc,

KoLBENLAUS.

Rostrum moderately long in the winged insects, but entirely wanting in the perfect sexes.

Antenna) three-jointed, the first and second short,and nearly equal. The third joint much the longest, roughly imbricated, with a circular tubercle near its base, and a longer, somewhat inconspicuous, tubercle towards its apex.

Eyes small and almost rudimentary in the apterous females.

Legs very short ; tarsi single-jointed, each furnished with two claws, two capitate bristles, and a cushion- like pad or pul villus.

Wing-membranes delicate; upper wing with a well- marked cubitus, from which spring three faint, oblique veins without any furcation. Lower wing with a vein- less cubitus.

Body globular in the queens, fusiform or ovate * From <p{i\\ov, a leaf, and Zvpov, withered, or from Knpalvaj.

PHYLLOXEEA. 43

in the later generations. In the larvaa the head is united to the body without any apparent constriction to form a proper thorax. Cornicles none.

M. Lichtenstein uses the tubercles of the antennas as specific characters in the genus.

This genus is, in a qualified sense, exclusively oviparous, for the true ovum applies only in strictness to the produce of the perfect sexes. Prof. Passerini has included all the known forms of Phylloxera under the tribe Chermesinas; but more recently M. Lichten- stein, who perhaps has studied this small group of insects as completely as any one, sees sufficient differ- ences in their habits and general characters to separate them not only from the ChermesinaB, but from the Aphidinaa altogether. Prof. Targioni Tozzeti also contemplates a similar dissociation, and has proposed that the group should be capitalised under the name Phylloxerites.*

I feel indisposed to assert how far Phylloxera has or has not a natural classification under the family of Aphides. Hard and fast lines of^demarcation are almost impossible to be defined for nearly allied forms, and much Avill depend on the relative values and importance given by systematists to any particular deviation from the type. For the present, therefore, I prefer to leave Phylloxera (which contains perhaps only a single known genus) to the family assigned to it by Passerini and other writers. Without such a grouping, indeed, the insects now to be described could have no place in this Monograph.

General remarks on the genus Phylloxera.

It may be well said that of all pestiferous Aphidian genera Phylloxera is the most destructive. Fortu- nately in this country we have felt no great injury from the only known indigenous species. From the

* 'Bull, de la Soc. Ent, Ital.,' 1875, f. 281.

4i BRITISH APHIDES.

circumstance that viticulture in the open country is but little attended to in England, no very serious evils have yet arisen from the far more destructive insect Phylloxera vastatrix, whose attacks are con- fined to the grape vine. It may be also said that no insect, large or small, has been honoured by such a voluminous literature as this destructive pest.

The appearance of some minute insects on the leaves of a vine growing in a greenhouse at Hammer- smith caused the Rev. M. J. Berkeley to bring the subject to Prof. Westwood's notice, and an article was written by that author on the same insect in the ■ Gardeners' Chronicle ' for 1863, p. 584. Prof. West- wood gave this insect the name of Perytimbia vitisana.

This small beginning has developed into the investi- gations of the commissions connected with the Govern- ments of France, America, Italy, the Cape of Good Hope, and elsewhere ; all of which inquiries have been conducted at the public expense. Their reports have been supplemented by valuable memoirs written by Lichtenstein, Planchon, Riley, Cornu, Signoret, Bal- biani, and a host of others. A large proportion of these memoirs are to be found scattered in the 'Comptes Rendus,' and the Transactions of the Natural History Societies of Europe and America.

Here we have another illustration of the natural fact that to the world at large the interest and the import- ance of a subject is often measured by the effect it may have on our social economy. The loss of many millions of francs or dollars to a country, leading to the decay of an important industry, forces numerous biological and scientific questions on the public notice, which, apart from such a stimulus, would be regarded with an utter apathy, and suggest thoughts that time spent in such a subject would be lost in puerilities.

The painful industry of the man of science who at his life-hazard studies the minute Bacillus, and traces its connection with tuberculosis or the fatal splenic fever — or again, investigates the sequence of such-like micro-

PHYLLOXERA PUNCTATA. 45

scopic organisms with cholera, has his high reward in the knowledge that he benefits his kind, and reduces the world's misery. The observation that the dry scientific fact of to-day may form part of the public riches to-morrow, is somewhat trite.

The genus Phylloxera was constructed by Boyer de Fonscolombe in 1834,* to receive the then unique Aphis Phylloxera quercus. The members of the group are now somewhat numerous, but only two species can, with certainty, be regarded as British. That on the oak is plentiful in our southern counties during some seasons.

Phylloxera punctata, Licht. Plates CXXI, CXXII, figs. i_6 ; and Plate CXXXI.

Phylloxera quercus, Walk. „ coccinea, Kalt. (?)

M. Lichtenstein, in 1877, gave a short diagnosis of an oak Phylloxera which he first found at Biarritz, and to which he gave the name Phylloxera punctata.

I append the substance of his remarks, as follows : — " I found the foundress in May at Biarritz on Quercus fastigiata. Her colour was white, irregularly spotted with red globules, which appeared to consist of internal granulations. She may be recognised by her long antennae. She surrounds herself with her eggs dis- posed in two concentric circles. I have not been able closely to study this species; but it ought to be common in the North, for I have seen it at Genthod, up in the mountains at Geneva, and at Bagneres-de-Bigorre; and Dr. V. Signoret showed it to me at Paris as being the type of Phyl. coccinea, of Balbiani, Hayden, &c.

" It is the palest in colour of all the Phylloxeras, in all their forms, and its pupa? appear to me relatively the largest. The sexated insects are whitish."

I have repeatedly taken this Phylloxera on the oaks

* ' Boy. de Fonsc, Ann. Soc. Ent. Fr.,' torn, iii, 223.

46 BRITISH APHIDES.

in my fields at Haslemere, but until lately I always regarded it as Ph. querent. I also some years ago received specimens of this same insect from the late Mr. F. Walker, who saw them surrounded by thousands of eggs in concentric circles, on some oaks near Shank- lin in the Isle of Wight. Like myself, he regarded this insect as Ph. quercus of Fonsc, and as such it appears in his ' Catalogue of Homoptera.'

A few months ago, M. Lichtenstein was good enough to inspect my drawings ; and he at once came to the conclusion that they do not represent the French and Italian Ph. quercus. The same gentleman kindly for- warded to me living specimens of the last, and 1 quite concur as to the identity of the British and Montpellier insects.

I believe the following account and diagnosis is the most complete that has yet been published.

Queen mother.

Inch. Millimetre.

Size of body 0'030 X 0-012 0*76 X 0*30

Length of antennae 0*010 0'25

Very small, flask-shaped, amber-yellow, occasionally spotted with red. Body smooth and not tuberculate. Head very broad ; eyes very small, black, and composed of three or four facets. Thorax hardly separable from the abdomen, which is globose, and terminated by apical rings. The apex furnished with an obtuse ovipositor, which is employed in ranging the eggs (which number one hundred or more) in two or three concentric circles on the oak leaves.

Antennae rather setaceous and tri-articulate. Eos- trum short, as also are the legs ; tarsi stout, each garnished with double claws and two capitate bristles.

The apterous larvae differ much both as to size and outline. This is partly dependent on the amount of eggs stored within them. The number of eggs capable of deposition by these apterous larvae is very

PHYLLOXERA PUNCTATA. 47

large, but the number mucli diminishes in the following generations. The eggs are at first quite smooth and shining, but very shortly afterwards show a corrugated appearance, which is caused by the extraordinarily rapid development of their contents. In the course of a few hours indeed the young Phi/lloxerce are disengaged from their membranes, and then they are comparatively active and stray away in search of nourishment.

Phylloxera punctata infests the under sides of the leaves of both varieties of the English oak. Some years at Haslemere, at Wanstead, and at Southgate, they are very numerous, but at other times I have found much difficulty in securing even a few specimens. The masses of pseudo-eggs appear as minute spots like honey ; and it often happens that the larvae of a small Scymnus or a minute Myina is employed in greedily devouring them.

Pupa.

Long, oval, ferruginous yellow, which becomes darker by age. Wing-cases brown; rostrum short. The pupae change into the winged insects about early June. The larvae undergo four moults before becom- ing pupae (Licht.).

Winged female. " Emigrante"

Inch. Millimetres.

Expanse of wings 0*170 4*31

Size of body 0*070x0*030 177x076

Length of antennas 0*010 0*25

Head and thorax broad. Abdomen tapered to a point, furnished with a blunt ovipositor.

Thorax disproportionately large, brownish. Abdo- men green, variegated with lighter spots, which show the pseudova within.

Antennae with three joints, the last imbricated and the longest, furnished with a long, tubercular indenta- tion covered by a membrane.

48 bbitish aphides.

Legs very short. Wings rounded at the apex; cubitus and stigma brownish ; membranes with three oblique veins, the first and second oblique closely approximate at their tips. Lower wings with a costal vein only. The insect figured in my Plate contained eight " eggs " of nearly the same size. Taken in September.

Late in the autumn much smaller pupae and alate individuals may often be traced in company with the normally-developed winged insects. These diminutive forms are a puzzle ; for they occur not unfrequently in other genera of Aphis. They have been in other species often, yet incorrectly, regarded as males ; but Balbiani has shown that they are partially developed females, which have somewhat an analogy with the neuter workers of bees and ants. These pupa? of Phylloxera punctata sometimes do not equal one quarter the size of the usual kind.

M. Lichtenstein has discovered the fact that, unlike most, if not all, other Aphides, the parent of the winged sexes is apterous instead of being furnished with wings to transport the perfect sexes to suitable situa- tions for oviposition. The same peculiarity obtains in another species foreign to England, viz. Phylloxera acanthocliermesi Kollar ; and if Phylloxera vastatrix fails to produce alate forms in any country, the sexes must here also develop from apterous insects.

The male and female. PI. CXXXI, figs. 1, 2, 3.

The insect which produces the perfect sexes of Phylloxera punctata is (unlike that of other Aphides) apterous. For this reason, amongst others, M. Lich- tenstein, who has studied this insect during this pre- sent summer of 1882, is inclined to remove the species from Phylloxera, and to place it in another genus, Aca/nthochermes, the " pupifer " of which he states to have always this peculiarity.

The sexes of P. punctata are very like those of P. tjunriis and P. caatatrix. They are without rostra,

PHYLLOXERA QUERCUS. 49

and therefore they can neither feed nor grow. The female contains one single impregnated eggt of large size.

Through the liberality of M. Lichtenstein I am able to add the following remarks which are the results in series of his observation on this insect.

1. The fundatrix or produce of the true egg.

2. She gives rise to the winged form (Emigrante), which lays her unfecundated eggs under the leaves of Quercus pedunculata.

3. These produce apterous insects (Gemmans), each of which surrounds herself with concentric circles of eggs.

4. These bodies develop apterous females (Pupiferce), which carry four or five ovoid envelopes of different sizes, one of which gives birth to the male, and the other to the female sex.

5. The apterous non-rostrated males and females produce

6. The fecundated egg ready to commence the new cycle.

M. Lichtenstein calls my attention to two small lateral tubercles on each side of the females. I omitted to notice these organs when I made my drawing. They are characters to be noted, but they occur also in Aphis papaveris, A. vibumi, A. Jacobosoe, &c, though in these last insects the papillaa are more numerous. Their economical significance is unknown.

Phylloxera quercus, Boyer de Fonsc. PI. CXXIII. figs. 1 — 10, Hartig, Lichtenstein, Riley.

Apterous pseudo-female.

	Inch.	Millimetre.
ize of body	0-030x0-015	0-76x0-38
, antennas	0-007	0-17

This insect hatches in early spring from the egg laid in Autumn. The egg is usually deposited in the VOL. iv. 4

50 BRITISH APHIDES.

crevices of the bark of the chermes oak, Quercus coed/era.

After several moults the insect assumes a flattish, flasked-shaped body, and becomes distended with pseudo-eggs, which are deposited, without any regular order, in small patches under the leaves. Wherever these insects congregate, a yellow or orange-coloured spot forms on the leaf, which penetrates through the substance and causes the upper surface also to appear brightly speckled.

The young hatched from these eggs are much more slender in shape, and become darker and redder at each skin-shedding, which occurs four times.

In about a fortnight they become pupge, and the first winged females appear late in May or in early •June.

At this stage all the winged insects are stated to migrate to the hairy oak, Quercus pubescens, and there they drop their pseud-ova. The resulting apterous females apparently do not give rise to winged forms until August. " Alors ces insects ailes, qui cette fois-ci ne sont plus porteurs d'eeufs, mais bien pupiferes retournent au chime kermes et deposent sur les feuilles lews pupes sexuees de dimensions differentes."* The largest of these are the true oviparous sexed females, the smaller are the males. After coupling, the result is a single fecundated egg much larger than any of the pseud-ova previously developed.

This ovum is the commencement of the new cycle, and discloses the queen-mother in the spring following.

According to Lichtenstein coupling in Phylloxera ijiirrr/fs is effected soon after birth of the sexes. The male is very ardent and visits many females. As they are born from the second winged individuals, which occur in September or later, doubtless the egg is lodged in some crevice in the oak-bark and remains there till the early spring.

* Vide M. Liclitenstein's notes at the end of this section of my Monograph, p. U3.

PHYLLOXERA QUEECUS. 51

No fewer than sixteen species of Phylloxera were named in America in 1875.* M. Lichtenstein thinks it safe to decide that only five well-defined species inhabit France, viz. P. coccinea, Heyd.; P. cortical is, P. quercus, P. punctata, and P. vastatrix.

I have not yet been able with certainty to identify more than the two last-named species as British denizens, and of these the vine Phylloxera must be regarded as a late introduction into these Islands.

Although the pseud-ova of Aphides take their origin from internal organs which morphologically cannot be separated from the true ovaria, the former should not be confounded with the true egg, which is always compounded of a true yolk and a germinal vesicle. Probably this egg would be wholly sterile without the influence of the male Aphis.

A slight examination of the abdominal contents of any viviparous female of Aphis will show that all stages of completeness obtain, from the minute nucleated point in the ovary to the well-developed young ready for birtb. These embryos are all included in an ovoid chamber, a kind of follicle ; and in many species the insects are excluded, still enshrouded in glistening membranes which appear very like eggs.

In early days it was often a subject for discussion whether the product of an Aphis was not always an egg, and there are several species of true Aphis which deliver their young so much in the form of ova, that they well might deceive the incautious observer.

Examples of such are to be found figured in this Monograph. Thus with Aphis petasiticlis, Schizoneura ulmi, and Pemphigus bursarius, the young do not extri- cate their limbs from their investments till some minutes after birth. The curious growth of these young from the pseudova which is sometimes seen, and which is very rapid, is caused by the inspiration of air

* Interesting information on the American Phylloxeras is to be found in Prof. Riley's Seventh Report on Noxious Insects in Missouri, p. 97, et seq.

52 BRITISH APHIDES.

into the tracheae of the live insects within ; I believe this expansion is never to be noticed with reference to the true ova. M. Lichtenstein has well distinguished between these separate ovoid bodies, so like each other, and yet so different in their destinations.

Notwithstanding that objections have been taken to the names proposed by Huxley for these two bodies, I think the terms of ova and pseudova (false ova), ovaria and pseudovaria, are very convenient ; and quite as intelligible as buds and gemmae.

But, after all, the phenomenon of viviparism may be looked at as a process in which the completed foetal development is effected within the parent, whilst in oviparism that same process is deferred for some con- siderable time, and in part is conducted externally to the parent.

From this point of view we might regard the whole family Aphidida) (Ohermes and Phylloxera included) as to their pseudova viviparous, but as to their real eggs oviparous ; the difference only being that in the genera of low grade the viviparous broods do not throw off their membranes until after their birth.* These mem- branes of the pseudova probably have no analogy to the chorion of the true eggt but may be regarded as mere sacs which enclose the embryos.

Phylloxera vastatrix, Planchon.

So much has been written on the vine Aphis, that it will be well to offer here only a short summary of the subject. For greater detail the reader is referred to numerous memoirs found in the 'Comptes Rendus,' 1 Annals Soc. Ent. de France,' and other sources, the chief of which are indicated in the bibliographical list at the end of this present volume.

Phylloxera vastatrix offers a good example of the

* Vide vol. ii, p. 70, PI. lviii ; also vol. iii, pp. 98, 118, PI. cviii, and PI. cxi, of this Monograph.

PHYLLOXERA VASTATBIX. 53

rapid spread of one animal, effected almost entirely through man's unwilling agency.

Thirty years ago the insect was unknown, although its existence in North America must date many thousand years back. Now it has crossed the Atlantic, spread over the greater part of Southern Europe, touched at Cape Colony in Africa, and brought its baneful influence to bear on the vineyards of Aus- tralia.

The earliest notice that I have found of the grape Aphis occurs in 1856, at page 158 of the First and Second Eeport on the Noxious Insects of the State of New York, by Dr. Asa Fitch. He there speaks of the " grape-leaf louse," which he names Pemphigus viti- folii. He describes the galls made by this insect as small and globular, about the size of peas, raised on the margins of the vine leaves in early June. These galls at that time contained only wingless females. He gives no printed diagnosis of the insects, but he refers to certain MS. notes which do not appear to have been published.

The Aphis mils viniferce of Scopoli and of Fabricius, appears to be quite a different insect.*

Although Phylloxera vastatrix was known in England in 1863, it does not appear to have reached California, in Western America, till 1871. Prof. E. W. Hilgard remarks on the modifying influence of climate as to the development of the aerial form, which condition may be thought to favour its rapid extension. Yet doubtless the introduction of the egg through the vine root has done infinitely more injury than any possible flight of the insect ; which must be confined to districts where the vine flourishes, and cannot extend itself over barren plains and oceans.

The vine Phylloxera is not indigenous to Great Britain ; but it has certainly been imported into our graperies and hothouses, where the even temperature seems favorable to its growth if permitted. The

* Scopoli, 'Ent. Cam.,' 398 ; Fabr., ' But. Syst.,' iv, 220.

54 JililTISH APHIDES.

comparatively rare winged forms, as well as the sub- terranean, have been repeatedly bred in England.

The occurrence of this pest at Hampstead has been before noted. Prof. Westwood,* who was only ac- quainted with the root-living state, named it in 1863 Peritymbia viUsami.

Mr. McLachlan has had more recently under his notice some vine leaves from Scotland, on one of which (only one inch and a half across) he counted thirty- five well-marked Phylloxera galls. If this vine had been left to itself, doubtless it would in due time have given forth those apterous forms which descend into the earth to feed on the roots.

Shortly after its appearance in England the insect invaded France, showing itself first at Tarascon in Le Gard, and then spreading through the Departments of Vaucluse, du Yar, de l'Herault, and the valley of the Rhone, and thence to Girond, Cognac, &c. Its march since then has been continuous.

Thus in 1880 the Phylloxera had spread over a large portion of the wine-districts of France. The pest has in great measure followed the course of the large rivers, whose banks have been terraced for vines. All the valley of the Rhone, from its debouch into the Medi- terranean up to Dijon in the Cote d'Or, is infected. A wide tract now spreads from Monaco and Nice, beyond Montpellier, even to the Pyrenees ; and a broad band of devastation extends in a line from Toulon to La Rochelle in the north-west. In 1877 only twenty- eight Departments had been visited, but in 18S0 these had increased to thirty-nine.

Messrs. W. and A. Gilbcy stated, in September, 1882, that in some of the brandy-producing districts of les Charentes the vineyards were giving way to cornfields. Herault, which furnishes about one-fifth of all the wine produced in France, is at this present time seriously affected; and the same maybe said of the Gironde, which has annually supplied Great Britain with six and * J. W. Westwood, ' Gard. Cliron.,' p. 584, 1863—1868.

PHYLLOXEKA VASTATEIX. 55

a half millions of gallons of wine out of the nine millions imported into the country.

As one twenty-fifth part of the area of France is now under wine-cultivation, it will not excite surprise that the authorities still offer a prize of 300,000 francs for a real remedy and abatement of an evil, which, in 1881, is said to have inflicted on this French industry a loss of three milliards of money.

From the foregoing it will appear that notwith- standing we possess the complete life-history of the insect, no sure, certain, and unexceptionable remedy has yet been advanced. Doubtless the ravages have in some districts been checked; and in others the Phylloxera has even been stamped out. Flooding the vines in winter has been found very efficacious, but this cannot be effectual on high levels. Arseniate of copper, carbon disulphide, phenic acid, and other chemical agents as insecticides, have been applied with greater or less success ; but such compounds, apart from their cost, are highly dangerous to human life.

As an insecticide, the substance known as sulpho- carbonate of potassium has been the most efficacious. M. Dumas happily suggested that the poisonous effect of carbon disulphide might be modified, by combining, the liquid with potassium sulphide. The resulting solid compound is far less volatile than the liquid, and it seems also to have the advantage of acting on the vine-stocks as a manure.

From the fact that the Australian vines are less liable, and are perhaps in some sorts even indifferent to the attacks of Phylloxera vastatrix, it has been argued that from a too select cultivation and grafting "in and in," the French stocks are not sufficiently robust to repel this insect, and hopes accordingly are still entertained that a large gain will accrue by bud- ding on new strains. The idea that the vine Aphis and other Aphides also, select the weaker plants, was strougly urged by the late Mr. Alfred Smee in his

56 BRITISH APHIDES.

papers on Aphis vastator in connection with the potato- blight.

On the other hand, it is averred that the healthiest vines, as being those possessing the most nutritious sap, are those chiefly selected, and most open to attack. Although soil seems to have but little to do with the evil, the wettest and the most sandy loams are generally the most free from Aphis infection.

The three chief diseases of the vine arise from the growth of the cryptogamic Oldcum Tuckeri, the injuries caused by the small pyralian moth GEhojphthira pell&riana, and this Phylloxera. Besides these, in hothouses we have the grievances caused by mildew and scale. Sulphur, hot water, or tobacco, are cures for these last; but the myriads of Phylloxera vastatrix in great measure have survived all attempts at exter- mination on the large scale.

M. Lichtenstein states that cavities are sometimes found in the bark of the French vines stuffed full of small black Aphides. These insects do not puncture the vine for its sap, but they have been transported thither, and form the stores of such predatory and minute wasps as Psen, Pemphredon, Cernonus, and the like.

Prof. Florel, of Lausanne, says that the Phylloxera was introduced into his district through the impor- tation of English vines into the graperies of Baron Rothschild in 18G9.

It was once thought that this pest could not pass the tropics alive, as the insect cannot bear dessociation from its food for a single week. Its appearance, how- ever, at the Cape of Good Hope, and in also Australia, shows that the eggs will bear considerable dessiccation without injury to their vitality.

Before giving a diagnosis of Phylloxera vastatrix I would make the remark that every moult which an insect undergoes has its significance, and corresponds to internal changes progressing within the body. It will thus appear how elaborate the history of any

PHYLLOXERA VASTATRIX. 57

insect would become, if every phase in its metamor- phosis should be fully studied and described.

In illustrating the development of the vine Aphis only a few forms can be here figured. This necessary restriction has been, indeed, applied to all the species I have attempted to set forth in this Monograph ; but, as a rule, I have chosen types of most marked phases. With reference to Ph. vastatrix the reader can consult the engraved plate issued by M. Lichtenstein in 1876, in which twenty-one forms of the insect are repre- sented. Some present lacunae may be supplied from thence. Any one attempting to draw twenty indivi- duals of the same species under the camera will remark the diversity of proportion of their organs at different times of their development.

Phylloxera vastatrix may be conveniently grouped for description into the aerial and the subterranean forms, which answer to the terms Grallascola and Radi- cicola of Professor Riley.

Aerial apterous female.

Fundatrix.

Phylloxera vastatrix, Planchon. PI. CXXII, figs. 7, 8, and PI. OXXIV, CXXV.

Pemphigus vitifolii, Asa Fitch. Peritymbia vitisana, Westwood. P)actylosiphozra vitifolii, Shinier. Phylloxera vastatrix, Lichtenstein, Riley, Signoret, Cornu, Balbiani.

Inch. Millimetres.

Size of the body 0-070x0-050 177 X 1'26

Length of antenna? 0-009 0*22.

Body nearly circular, flask-shaped, drawn out at the tail, which ends in a short and truncated ovipositor. Colour amber-yellow, fuscous, or ferruginous ; spotted

58 BRITISH" APHIDES.

from the numerous eggs which fill the body-cavity. Head- and tail-ends slightly browner. Eyes black and very small. Antennas short and very fine, three- jointed, the last being much the longest. Legs very small, scarcely protruding beyond the body. Rostrum about one-fourth the length of the body.

This insect is the immediate produce of the true ovum, which was laid in the autumn by the sexed female. Her history, after exclusion from the egg, is probably somewhat different according to the climate, and, perhaps, the character of the vine on which it occurs.

The aerial forms are rare in the colder countries, but they increase in frequency as we go southwards or cross into America. Where the aerial forms occur, the foundress punctures the leaves in such a manner that the swelling masses close over and finally entomb her. The leaves become studded over the surface (and particularly near the edges) with gall-like masses, many of which are pedunculate. Each foundress appears to form a single gall, within which she lays hundreds, or even thousands, of yellow egg-like bodies. This oviposition continues through the summer, after which operation she dies.

These galls are round, fleshy, and corrugated. They often number a hundred or more upon a single leaf. A vine which is much infected soon becomes sickly. The leaves show distortion, turn yellow or brown, and during their decay yield a faint and unpleasant odour. The stocks become stunted, and if the roots be uncovered they will be found (especially as regards the fibrils) swelled into small blebs and tubercles. These are the result of the attacks of the young Phylloxeras, which, after their development on the leaf and escape from the gall, have descended into the ground and commenced their subterranean exist- ence. These creatures are so numerous that the roots wlicn turned up often appear dusted with yellow grains. In this condition they produce the greatest

PHYLLOXERA VASTATRIX. S9

destruction to the European vines. In America the aerial form appears to produce the greatest evil.

Subterranean apterous female.

These apterous larvse are smaller than the f undatrix, and measure 0*026 X 0*01 6 of an inch. They are amber- yellow, with an olive stain towards the head and vent. In later generations the forms are more flask-like and colour ferruginous. During their life underground they oviposit. One specimen, however, on dissection contained only eight eggs, but this number is not con- stant. The egg-like bodies are of a pale yellow colour and shining. When the larger roots are attacked the cortex is loosened ; it rots and scales off under the irritation of the insects, as seen in PL CXXIV, fig. 5. When the small fibres are affected, swellings and nodules mark the injury done, as seen in PL CXXV, fig. 10.

Professor Riley states that this root modification of Phylloxera passes through five or six generations, which fact will account for the various forms and sizes seen simultaneously crowding the roots of the plant. The American forms appear to be more tuberculate than those I have been able to examine through M. Lichtenstein's courtesy.

About the month of July many of these underground forms pass into nymphs and come to the surface, where they develop wings, and then they fly to distant vine- yards to carry on the invasion. In America during August they swarm in thousands. A quart pot of earth containing infested roots will for three weeks yield a dozen of these alate forms daily, each of which contains one, two, up to eight egg-like bodies of dif- ferent sizes, which are deposited sometimes under the leaf, and sometimes in the fissures of the bark. This winged insect is the " Pupifer " of Lichtenstein, and furnishes through the above pseudova the true males and females.

60 BRITISH APHIDES.

Winged (pspudo-) female.

Inch. Millimetres.

Expanse of wings 0-120 3*04

Size of the body 0-045x0-015 1-14x0-38

Length of antenna? 0-015 0"38

Body greenish-yellow, fusiform. Abdomen tapering towards the apex. Head broad. Eyes large and red. Antennae rather short, third joint much the longest, strongly ringed, and apparently without any marked tubercle. Wings carried pentwise, membrane hyaline and very delicate. Cubitus broad and yellow. Stigma very faint. The three nervures pale yellow.

The only specimen I have examined contained one single large eggt measuring 0'015 of an inch. The identity of species of these aerial and subterranean insects is now too well-known to require comment ; beyond the fact that Professors Riley, Balbiani, and Cornu have all proved that the two kinds may be compelled by artifice to change their habitats. The apterous larva) taken from the roots, however, show much disinclination to feed on the leaves, and probably they never would raise the galls.

Prof. Balbiani has shown that the appearance of the winged insect is not necessary to complete the cycle of life. In this case, when a recurrence to the male becomes necessary, an apterous form must yield the eggs which give rise to the sexes, just as it occurs in the case of Phylloxera pimctata.

The American Phylloxera appears to have as many as six different periods for egg-laying ; but the Euro- pean insect, from Lichtenstein's observation, would appear to have fewer. The root-feeding larva) undergo a hybernation, during which time they shrivel up without losing vitality. In April they wake up, be- come supple and inflated from the imbibition of sap, ;m<l then it is that the chemical insecticides have the greatest activity upon them. Extreme cold does not much affect the ova of insects. M. Girard points out

PHYLLOXERA VASTATRIX. 61

tliat the egg of the silkworm will bear a cold of 25° C. in their passage over the mountains of Japan, and that the caterpillars may be frozen, " so as to ring like metal on a marble slab," and yet after a slow thawing they will come to life and feed like others. The fond hopes that cold would destroy the hybernating egg of Phylloxera cannot therefore be realised.

Balbiani states that the winged females deposit their pseudova amidst the down on the underside of the leaf ; and Riley says that this is the common habit of the American species. The insect, however, will drop them on the bark, or stem, or indeed almost any- where.

The produce of these last egg-like bodies, which differ in size, is the true female from the larger, and the male from the smaller variety. The sexes are both mouthless, and live only for reproduction. The male is comparatively active and visits many females, from which it would appear that the last sex is in excess.

The male and female. PL OXXII, figs. 7, 8.

These perfect sexes I believe were first discovered by M. Lichtenstein, and afterwards by Prof. Riley in America. They are exceedingly small, and have no true mouth parts. A small eminence is the sole representative of the buccal organs.

The apterous male.

This minute insect is pale ferruginous yellow, cycloid, flat, testudinate, with a very broad head furnished with small black eyes. Thorax proper there is none. The abdomen is coarsely ringed and corru- gated. Legs short, with obtuse tarsi and very minute claws. The male is so small that it may be easily overlooked.

The sexed female

is much of the colour of the male but is larger. The

02 BRITISH AMIDES.

abdominal cavity contains a single egg which is the true ovum. The female delivers herself of it about the fourth day after she is hatched, and this without any real necessity of concourse with the male. Whether such eggs are barren it does not appear (see Riley, Eighth Report, p. 159). The true ovum is larger than all the preceding pseudova. It is yellow at first, but soon afterwards it becomes olive in colour with a rough exterior. Its survival through the winter in the crevices of the bark has been substantiated by Dr. Balbiani and M. Lichtensteiu, and there is no doubt that the fundatrix is the produce of the same, just as with all other Aphides.

It has been stated that the Phylloxera keeps below the soil in dry weather, but ascends the stocks in the wet season (Villedieu).

M. Lichtenstein lays much importance on the fact that the males and females remain for several days after they have been deposited by the winged insect in certain delicate membranes, which at one time he regarded as cocoons. ' The reason why he now con- siders these egg-like bodies as pupaa (nom donne par Latreille aux chrysalides qui sont formee par la peau de la larve se durcissant autour de 1'animal) will be found in the general summary of the genus Phylloxera, with which he has obliged me.

I gather from his remarks that, when two winged generations appear in Phylloxera, the first produces a rostrated progeny, and the last a non-rostrated. If the vine Phylloxera shows but one alate generation, it furnishes the non-rostrated sexes, in the autumn. He warns all investigators against the confusion likely to arise by confounding an alate insect with its later winged successor.

If there be no aerial forms in a cycle, the foundress descends at once to the roots and no galls appear on the leaves.

In concluding my diagnosis of such Phylloxeridaa as have come to my notice, I introduce to the reader the

PHFLL0XERID2B. 63

following valuable summary. M. Lichtenstein is accomplished both as a biologist and a linguist, and the reader will note not only his concentration of the sub- ject within a small space, but also will appreciate the clear English he employs, of which language he has made himself a proficient. I here heartily thank him for the material help he has given me in the preparation of this Monograph.

Summary on the Genus Phylloxera. A Letter ad- dressed to the Author by M. Jules Lichtenstein

La Lironde, Montpellier ;

September 10th, 1882.

My dear Sir,

You ask me to give you a note on the genus Phylloxera, which I have now had under particular observation ever since 1868. I am sorry to say I am not able wholly to explain in a satisfactory way the very curious metamorphoses of these Proteus- like insects, which seem to defy the endeavours of naturalists to group them by sharp and rigid characters.

As you have already mentioned in your work on ' British Aphides ' my ideas about the biological evolu- tion of plant-lice in general, and gall-lice in particular, I can spare your readers a good deal of explanation ; and begin with a short affirmation of a theory, which is now about ten years old, and which all my sub- sequent observations lead me to confirm.

With reference to the hypothetical frame I have fancied of Aphis evolution, I will shortly indicate what I know surely to be true, and what I suppose to be so, but cannot as yet bring to rigid proof. First of all I am of opinion that the evolution of plant-lice is entirely different from the common metamorphosis of other insects ; and, as Baron von Gleichen, De Geer, and Gotze said before me, I think the only way of

64 BRITISH APHIDES.

understanding the various life-stages of a plant-louse is to compare it with the growth of a plant.

The egg, which is often single in the females of Aphides, is not destiued, as in other insects, to pro- duce a sexuated male or female ; it furnishes only an a //anions form, which by a sort of budding process (bourgeonement or gemmation in French, Keimung in German) reproduces a great number of individuals able to continue this budding reproduction for a more or loss prolonged period, until there arrives a period in which the produce of these gemmations consist no more of agamic individuals all equal, but sexuated insects, male and female, which last lays the fecundated egg, and gives origin to a new series of beings.

As I said before, this kind of evolution calls to mind that of a vegetable, from the seed of which arises the trunk, branches, leaves, and flowers by gemmation, giving at last, once more, the fecundated seed, through a kind of copulation. I suggested for the agamous forms — thus able to reproduce by budding, the name of Pseudogynae ; and, considering them to be only transitory or larval forms, I gave the four life- stages preceding the appearance of the sexuated insects the following names :

1. Pseudogyna fundatrix.

2. — migrans.

3. — gemmans.

4. — 2)UlJtfGra'

I retained, of course, the names of male and female for the sexuated forms, which show the genital organs and are able to copulate. I called the first form issuing from the fecundated egg the fundatrix (as a translation of the German word Stammiitter), thus indicating the first foundress of a colony. This is the insect which generally forms the galls in those species where galls are produced. Nevertheless, in some species the power of forming gall-like swellings is not

PHYLLOXEUIDiE, 65

limited to the Pseudogyna fundatrixy e.g. Phylloxera vastatrix.

The name of Pseudogyna migrans was suggested by the fact that in the greatest part of plant-lice the second form is winged and flies away from the place where it was born. Yet here, as in the preceding case, there may be exceptions, and some kinds do not leave their birthplaces. Still, I regard emigration as the rule.

I gave the name of gemmans to the form succeeding the emigrant, because it is the curious period in which the budding reproduction gets to such a height, that Bonnet was able to obtain without access of the male nineteen generations from Aphis sambuci. Kyber, of Eisenach, and later Schrader, of Bordeaux, noted four years' reproduction from Siphonophora rosaz and Phylloxera vastatrix. As to this last one, I am my- self well convinced that the power of reproduc- tion of the underground Pseudogyna gemmans of the root form, has occurred in a piece of vineyard of my own property ever since 1875, and the pro- cess is probably everlasting. Of course this will happen only as long as food and temperature allow it, because the two conditions of heat and nourish- ment have the greatest influence on the repro- ductive power of the agamous-gemmans form in all Aphides. Here also, as in the two preceding states, numerous exceptions to the rule find place ; for if it is possible and even easy, by maintaining Aphides on fresh leaves or fresh roots in warm rooms, to obtain constant reproduction, it will occur more frequently that the want of food in the cold season will kill the gemmans-phase, or oblige it to undergo the last metamorphosis, and then become what I call the Pseudogyna pupifera.

This last name has been criticised more than once. I would indicate by it the form which produces the sexuated insects. I wished to establish by the word pupifer that it is not an eggt but a true pupa or

VOL. iv. 5

66 BRITISH APHIDES.

chrysalis of two different sizes, giving birth to males and females. These last are laid by the Pseudogynce of the fourth stage.

I must acknowledge that the word pupifer is not perfect ; as in many species the males and females are born alive, because the fine skin by which they are surrounded bursts at the moment of laying.

However, I gave all names after a full consideration of the biology of Phylloxera querc&s ; and as in this species the sexuated insects remained some days in their egg-shaped pupa3, I inadvertently selected a name which is not equally well adapted to all Aphides.

Of the sexuated forms, male and female, I have little to say. The females seem always to be apterous, the males occur both with or without wings in the same genus, and even in the same species.

I now hasten to describe my classification of the genus Phylloxera — or I would rather say of the family Phylloxeridse, for I think it is not possible to retain under the same genus the numerous species already known.

Phylloxerire.

These are easy to distinguish from all Aphides by their three-jointed antennas, shown in all their life- stages. This is a good plastic character, and separates the Phylloxerians from all other insects of their class. It is a fact that each of the four life- stages of the above-mentioned family is separated from the following one by an egg-like quiescent state; so that the Pseudogyna1, which seem to be viviparous in other Aphides, here appear to be oviparous. With the Phylloxerians these may be looked upon as pseudova.*

* I have had no opportunity to study the Chcrinesians, which are, ]n ili.i).-. also oviparous ; but the genua Vacuna, which is mentioned by Borne authors as oviparous, I can testify is certainly viviparous.

N.B. — J\Iy own observations on Thelcutee dryophua | Vacu/nai) also pul la. i beyond doubi However, Vaouua has boon confused with Phylloxera by Borne authors. — G.B. B.

PHYLLOXERIDJE. 67

The European representatives of the genus Phyl- loxera were limited about fifty years ago to one single species, named by Boyer de Fonscolombe Phylloxera quercus. This author mentioned the insect as feeding on Quercus pubescens and Q. cocci/era. His observa- tions on the insect were correct, and I can establish the evolution of the species as follows :

1. Egg deposited in the bark crevices of Quercus coccifera.

2. Foundress, or Pseudogyna fundatrix, feeds on the same tree.

3. Pseudogyna migrans, as larva and nymph, feeds on the same tree, but after getting wings emigrates to Quercus pubescens.

4. Pseudogyna gem/mans feeds under the leaves of Quercus pubescens.

5. Pseudogyna pupifera feeds, as larva and nymph, on the same tree ; but after getting wings flies back to Quercus coccifera to deposit on the leaves the pupae out of which the males and females issue.

6. These last, after union, deposit their single egg in the bark crevices, where it passes the winter.

When I first published the above observations many able entomologists doubted their correctness ; but shortly after me Prof. Targioni Tozzetti, of Florence, found that the same cycle of life occurred in another species of Phylloxera, that is to say, Phylloxera florentina, Targioni. This insect is born on Quercus ilex, the evergreen oak, and passes the summer on Quercus sessilijlora.

Thus, two species of Phylloxera have been proved to migrate from the deciduous to the evergreen oak ; but, as the ilex group is a southern species, it is probable that neither Phylloxera quercus nor P. florentina occurs in Great Britain.

The following four species appear to undergo their whole biological evolution on Quercus robur or its varieties :

68 BEITISH APHIDES.

Phylloxera coccinea, Heyden.

— corticalis, Kaltenbach.

— punctata, Lichtenstein.

— acantho-chermes, Kollar (sub. Acantho-

chermes quercus).

The yellow, black-spined Phylloxera corticalis feeds only on the trunk and twigs of Quercus pubescens, and was found by Kaltenbach at Aix in 1862. Its habitat does not allow one to confound it with any other species. I believe its economy is similar to that of Phylloxera (j uc re us, but without its migration. I know the Pseudogyna migrans, gemmans, and yupifera. I have not yet obtained the sexuated forms.*

Phylloxera coccinea, P. punctata, and P. acantho- chermes all feed under the leaves of Quercus robur. P. coccinea forms a gall-like folding of the leaf-edges, under which it lays the pseudova from which the emigrants issue.

I am not sure if these become winged ; for about the time in which that metamorphosis ought to take place, clouds of emigrants of Phylloxera quercus arrive on the same trees, and I have not been able satis- factorily to isolate one species from the other. The foundresses {Pseudogyiuv fundat rices) of each species are very different. In Ph. quercus she is active, large, and tuberculated ; whilst in Ph. coccinea she is quite smooth, and lies in a gall. This last insect is found also at Paris, and was discovered at Frankfort by von Heyden. I received winged pupifera) from M. Signorot, which furnished me here with pupce, from which I obtained males and females.

I consider Phylloxera punctata to be an inhabitant of the mountains, having seen it only in Switzerland and in the Pyrenees. Here we meet with the unusual circumstanco that, while in all the preceding species tho pupiferous form is winged, it is apterous in Phyl- loxera punctata. Thus the pupa3 of two different

* Since tliis was written I obtained in my breedings the very small Kcxuat< (1 forma of that species on the first of October.

PHYLLOXERIDJ!. 69

sizes, enclosing males and females, are laid by an apterous individual.

The last of these species feeding on the oaks is Phylloxera acanthochermes : and it partakes also of the above anomaly of showing the pupiferous form wing- less. I can say very little more of this curious Aphis than what Kollar has told us. It is surrounded in its gemmans period with star-shaped appendages, which, remind one of the coccido us mealy-bugs (Dactyl opius). I have had only one opportunity of examining it at Bordeaux, and then I chanced to obtain the apterous Pseudogynoe pupiferce, which produced pupge, out of which I obtained males and females. The first life- stages of this insect are unknown.

There yet remains for description the dreadful nuisance of our vineyards, Phylloxera vastatrix. It is, however, so well known that I can hardly add any new facts to the very complete information given by my excellent friend Riley in his interesting Reports from 1869 up to this day.

Introduced into Europe about twenty years ago, it has in its struggle for life destroyed the best vineyards of the Continent. Professor West wood, the " actual prince of Entomology" (as we used to call Latreille), has described the gall-making form (fundatrix) under the name of Peritymbia vitisana, a name well adapted to the habits of the foundress whilst surrounding her- self with the gall in which she must die. If, for the scientific world, sub-genera are to be created for the grape-louse, this species should be called Peritymbia vastatrix.

As I limit myself here to a biological sketch of the different species of Phylloxera, I will not enter on an examination of the plastic characters which distin- guish the grape- from the oak-lice. The form of the impression on the third joint of the antennas, which is elongated and oval in the oak-species, and circular in the grape-louse ; is perhaps the most easy character to seize.

70 BRITISH APHIDES.

In its biology and evolution Phylloxera vastatrix — half aerial and half subterranean, is different from all the other species. According to my views ; the cycle of life is, I believe, as follows. There is but one generation in the year, thus :

1. The egg, deposited under the bark of the vine in the winter.

2. The Pseudogyna fundairie, forming galls on the leaves in May and June.

3. The Pseudogyna migrans, issuing from the galls and descending to the roots. July.

4. The Pseudogyna gemmans, feeding on the large roots. August.

5. The Pseudogyna pupifera, feeding on the small roots, where they form tear-shaped swellings. These insects issue from the soil as nymphs, and obtain their wings in September. They fly to the vineyards to deposit their pupae under the leaves, out of which the sexuated forms appear. After union, the female goes under the bark, where she lays her single egg and dies. October.

But I fancy this simple cycle may be modified in the American insect. It may change under the influence of a climate and food entirely different. Two or three centuries hence may perhaps show the transformation of this species; but even now we witness some altera- tion of habits. In the northern parts of France wherever I have observed the grape- Aphis its evolu- tion is a slow one. It conforms to the above general description with this difference ; that the foundress goes at once to the roots because the leaves of the European vine do not seem adapted to produce galls. Evolution becomes always more rapid as we proceed southwards. Thus, whilst in Germany and Switzer- land the winged form is very rare, and appears in September, I found it at Aix in Savoy in August. At Lyons it appears in July, at Montpellier in June, and Malaga in May. Again, I had roots experimented upon in the hot-houses of the Botanical Gardens of

PHYLLOXERID^E. 71

Montpellier, and I obtained the winged Pseudogynre in March ; so it is easy to conceive that, according to the climate — and perhaps also to the difference of food and other circumstances, insects usually elsewhere having one brood in the year may have two or more.

If we consider that we have to deal with the family of insects where, besides the sexual, there is an agamic reproduction, extending perhaps to an infinite series, there is no wonder that in southern climates we find thousands of acres of vineyards destroyed in the course of a year or two. Although we see these insects so alike in form that it is not easy to find plastic cha- racters sufficient to distinguish one from the other ; yet in their biological evolution a tolerable classification may be made as follows :

On oaks. — Emigrant species.

From Quercus coccifera to Quercus pubescens. Phyl- loxera quercus, Boyer.

From Quercus ilex to Quercus sessiliflora. Ph. florentina, Targioni.

Non-emigrant species.

Feeding on the bark. Pupifer winged. Ph. cor- ticalis, Kalt.

Feeding on the leaves. Foundress in a gall. Pupi- fer winged. Ph. coccinea, Heyden.

Foundress (?). Pupifer wingless. Ph. punctata, Licht.

First stage unknown. Pseudogyna gemmans in a Swelling of the leaf. Pupifer wingless. Ph. acantho- chermes, Kollar.

On vines. — Evolution partly aerial and partly sub- terranean.

First stages all apterous. Pupifer winged. Ph. vastatrix, Planchon.

M. Lichtenstein closes these interesting remarks on the Phylloxeridse with a warning that much confusion may arise by mistaking the winged emigrants for the second winged generation or pupifer. This last form alone produces the mouthless males and females.

72 BRITISH ArHIDES.

Before dismissing this portion of my subject, I wish to make the following short comment to prevent misapprehension :

Whilst fully sensible of the value of much that M. Lichtenstein has written on the Peruphiginaa and Phylloxerina3, I would guard myself from a committal to some of the theories he has put forward, such as the periodic migration of Aphides from one food-plant to another; and particularly as to his observations, that certain species feed on the leaves of the oak, and subsequently descend to the roots of grasses for hybernation. I find it the more necessary to make this reservation, since M. Lichtenstein in the ' Comptes rendus ' for December 4th, 1882, uses my name, together with others, as an authority for these points in the economy of these insects. The utmost that I can say is, that though all analogy in other insects is against such migrations, the results of experiments, if rigidly correct, must really control preconceived notions.

M. Lichtenstein distinctly states that he and his friend M. F. Eichter have bred the winged Tetranewra ulmi from certain larvaa feeding on the roots of Tritirum repens (chien-dent). Of course if this be so, and no mistake has been made in identifying this species, other biologists will soon corroborate observa- tions of such curious habits. I would say for myself, that I have not noted such an economy in the English Tetrancura, Pemphigus, and Phylloxera. I prefer, therefore, for the present, to hold my judgment in suspension.

Again, where I have used the words " emigrante " and " pupifere," I have done so, to distinguish the first alate brood, which wanders from one tree to another of the same kind ; from the second alate brood, which generally produces the true sexes. I think the word " pupifere " is not a happy one, for it is likely to mislead. Still, as may be seen in a few pages back, M. Lichtenstein has given his matured reasons for

PHYLLOXERID/K. 73

retaining the term. The reader is referred to the above paper in the ' Comptes rendus,' p. 1171, for various details connected with the habits of this and other species observed by M. J. Lichtenstein.

"With reference to the word pupifera as employed byM. Lichtenstein, Dr. Balbiani makes remarks to me, which accord with my own opinion on the matter.

He says : " Si Ton doit appeler des ceufs de corps qui sont constitues essentiellement comme les ceufs des autres insectes, qui se segmentent, et dans les- quelles, les parties de Pembryon se forment successive- ment et peu a peu ; ces corps sont des ceuf et non des pupes comme je l'ai toujours soutenu."

I may mention also the coinciding opinion of Prof. C. Riley on this subject, who speaks of the u insufficient and misleading nature of the theory regarding the evolution of the Aphididae ; whilst calling the winged females larvce and their eggs pupce" &c.

Vide ' American Naturalist,' xvi, May, 1882, p. 409.

I have obtained M. Balbiani's kind permission to translate and publish a portion of a letter addressed to me, which is of considerable interest ; since it con- verts into a clear proof that which previously had only been a conjecture. The discovery here noted accounts for the total disappearance, for many months above ground, of such Aphides as feed exclusively on the leaves of annual plants. As M. Balbiani's obser- vations have not been published they will be the more acceptable. In an economical point of view they will have interest to the hop-grower, since they will direct attention to the probable winter nidus of the egg of the Aphis which so often suddenly ruins his expecta- tions of a fine crop of blossoms : expectations which he had a right to calculate upon from the previous healthy condition of the vines.

This letter also has some bearing on the mooted question of migration, and I quite agree with the writer that there seems to be no necessity for any theory of migration from one plant to another of a different

74 BRITISH APHIDES.

kind in those species of Aphides which, like Pemphigus, Tetraneura, and Phylloxera, get their nourishment from ligneous trees and plants ; for on the same vegetables they not only feed but secure safe harbour for their eggs during the winter. It is chiefly with reference to those Aphides which live on annual plants ; the stems of which die down every year, that it would be interesting to know what becomes of them during the many months in which no food appears to be provided for them.

Dr. G. Balbiani informs me in his letter, dated January of this year, that " In the Bois de Meudon, near Paris, Siphonophora millefolii was exceedingly common in 1866. Colonies were very abundant upon almost all the tufts of Achillia millefolium, which plants were almost covered by them. In autumn the males and females appeared, and I many times witnessed the coupling of the red-winged males with the apterous females, which last were green like the agamic individuals. During nearly a whole month during which I observed them, I never saw one egg fixed to :i leaf or to a stem of Achillia."

" I then examined the turf below, and to my surprise I found a large quantity of eggs which were nearly black and sticking to the leaves of several grasses and plants as Gyperaceat Trifolium prateme, &c.

" I took home with me several handfuls of these sedge plants and grasses, and at the end of February, L867, they were covered with a number of active little ' puccrons ' of Siphonophora millefolii."

We may conclude, therefore, from this observation ; which has a bearing on the history of other Aphides living on anniml plants, that when the females have coupled fchey quit the branches and lay their eggs in the soil on grass or on any vegetable <lr/>n'i< which will remain throughout the winter. Thus these progenitors shelter their eggs even more securely than the progeni- tors of those which oviposit on plants. M. Balbiani further tells me that he has also made observations on

phylloxeridj:. 75

Siphonophora solidaginis, but the results are less com- plete than those of 8. mittefolii.

In September the males and females were often seen coupled together under the flower heads of Solidago, but singularly, as in the other mentioned case, the egg was never detected on the food-plant. The gravid females descended the stalks, and might be found at all heights, more than two or three inches from the ground.

M. Balbiani thinks that these Aphides abandon the plants of Solidago vergaurice, which, in summer, harbour the viviparous broods, in order to lay their eggs on some of the low plants in the immediate neighbourhood; exactly as has been seen to be the habit of Siphonophora millefolii.

V. BHIZOBIINuE, PASS:

WINGED FORMS UNKNOWN.

KHIZOBIIN^]. 79

INTRODUCTION.

Classification is based on certain observed affinities and agreements with types, or divergencies therefrom. In proportion as a grouping of animals accords with their biology, morphology, and the like, will any given arrangement assume a scientific value. It is, however, obvious that all classifiers do not attach equal value to the same characters. A consensus of opinion, however, will render any schemes they may raise more likely to be in accordance with natural laws.

Genera, however, may be temporally adopted for mere convenience and a means of study, until such time as a better acquaintance with embryology and a true phyllogeny will permit a more perfect grouping. These remarks will more particularly apply to the tribe immediately following.

Perhaps of all divisions of the family Aphidiuse no group presents so great difficulties in classifi- cation as that which Passerini has marked under the sectional name of RhizobiinEe. The fossorial habit shown by all the known species, and their attachment to the young roots of various plants, is by no means confined to Aphides of this tribe. We have noted subterranean habits in Sipho- nophera, Aphis, Pemphigus, Schizoneura, Paracletus, and Trama, therefore the meaniug of the term is not exclusive, as a generic term should be. Linnseus's well-known words, " Nomina si nescis, perit et cognitio rerum," may go too far; but a name is a first step towards an exact knowledge of a thing. It may be a question whether the names of genera should ever express or involve an hypothesis.

Burmeister described a species which burrowed at

80 BRITISH APHIDES.

the roots of Hioracium, to which he gave the name Bhizobiu8 subterraneus. Signor Passerini, for conve- nience, has adapted its characters for a sectional group, and I here follow the lead of so good a naturalist.

No winged forms have yet been discovered in this group. Thus we lose the valuable help which would have been afforded by a study of the wing-veining and other characters attending a metamorphosis into the imago. Again, the simplicity of the tarsal joints, and the little light thrown on the matter by any reliable variation in the mouth parts, and the want of all fixed banding of pigment or colour on the bodies, render it very difficult authoritatively to decide what should be the points of a diagnosis.

As an illustration of the variability of a genus I cannot do better than quote Passerini's words, which, though they apply particularly to the description of a single insect, Bhizobius menthce, yet equally well suit all the English species of this tribe.

With reference to the antennal joints, he says, 11 Secundum astatem antennarum articuli numero vari- ant. In junioribus articuli tres tantum extant, quorum extremus caateris valde longior. Orescente state hie apico dividitur, unde antennas quadri-articulatae fiunt; et deinde articulus tertius, omnium sua vice longior, apicem versus bis dividitur donee antennae sexarti- culataa evadunt, articulis subaequalibus."

Notwithstanding these undefined characters, consi- derable interest attaches to the group on account of the peculiar economy shown by its members. When the insects are regarded as a whole, they certainly show to the eye a peculiar aspect, which separates them from all the genera previously described.

One of the notable life-peculiarities concerns their relations to ants. With few exceptions, all the species are denizens of ant-hills ; and it is singular how insects of such diverse habits and conformation can live and thrive together.

Many isolated observations have been made with

RHIZOBIIN^]. 81

reference to this very curious subject of what may be called Paracletism. More correctly, perhaps, its dis- cussion belongs to the historian of Formica than to that of Aphis, since the Ant, with its superior intelli- gence (?), chooses the company of Aphis, and makes it more or less to conform to its own economy.

But the question arises, and has not been yet satis- factorily answered, what part in the economy of Formica, &c, does Aphis really take ? From the days of Huber the older, and the younger, we have been aware that Ants draw occasional food from these creatures, and this Monograph has already noted that many species of Aphis voluntarily yield honey-dew from their nectaries at the call of the Ants ; but what is to be said of those insects which possess no nectaries, as is the case with the Bhizobiina3 ?

True, they have certain dorsal pores apart from the stomata ; and in some cases the aerial drops of liquid may be seen to exude from such orifices.

In these root-feeding Aphides, however, the func- tion of the pores is to exude waxy or silk-like fila- ments, which are employed to cover and protect the insect from the water of the soil and to make a nidus for its eggs. I am far from denying that these pores are capable of giving food to the Ants, but clear obser- vation to substantiate the fact is yet desirable.*

Perhaps this question may be relevant to the matter : What is the significance of the presence of the blind Claviger, of Julus,of Oniscus, and Scolopendrum, which equally share the shelter of the Ants' nest ?

It cannot here be argued that they are kept by the Ants for food. The whole question is an interesting one, and is sufficiently puzzling ; for these curious fostering habits obtain also in other Hymenoptera. Thus, the handsome Apathus barbatellus is the petted,

* Kaltenbach is distinctly of this opinion. He says of Forda, " Dieses Thierchen gibt durch die Afterwarze zuweilen an Tropfchen Fliissigkeit von sich, welche von den Ameisen begierig aufgeleckt wird."— Kalt., « Mon. der Pilau.,' p. 210.

VOL. IV. 6

82 BRITISH APHIDES.

but apparently idle, tenant of the nest of the common humble-bee, Bombus terrestris, and numerous similar examples may be cited.

As regards the association of ants and Aphides it may be remarked that the light, sandy, and warm locality chosen by Ants for their nests arc just those which the subterranean Aphides would choose. Mr. James Hardy, the active naturalist, of Cockburns-path, Northumberland, who has paid attention to the root Aphides not uncommonly found on the moors around writes to me, " "When Fordaformicaria prevailed in the nests of Formica fuliginosa I noticed that the ants paid no attention to them when the hillocks were disturbed. The Aphides slowly re-covered themselves with earth, and those which failed to do so were left quite unnoticed by the numerous ants running about them." In other cases, and notably in that of Formica umbrata, shortly after a similar disturbance, the Aphides were carried off by the Ants, " and they and I had a contest about a particular example."

The Ants are in the habit of keeping open runs to carry their offspring nearer to the light and heat, and these runs afford convenient and free spaces also for entrance of the Aphides.* In many cases the Ants doubtless choose for their nest such tufts of grass on a dry hillock as are already infested by Aphides. This is a more simple operation than a marauding expedition, attended by a forcible transplantation of Aphides from the leaves of plants to subterranean cavities, as noted by Huber. Such a change of life seems to be very improbable, and involves so many difficulties which it would be well to have removed.

Goedartf was I think the first to observe the

friendly relations between Ants and Aphides. He

went so far as to imagine conversations between the

two insects relating to the attacks of their enemies

and the like.

* Kale. • Hon.,' p. 210, " Veini Zutritt dcr kiihlern Luft von den meiscn in eleven Gauge gesohleppt." •f- Goedart, ' Do Inscrtiw.' London, los.y

FORDA FORMIOARIA. 83

Genus XXXII.— FORDA,* Heyden. Ant-Aphis. Ameisenlaus.

Antennas 5 -jointed, the last articulation furnished with a small tubercle or nail. The third joint much the longest. Eyes very small. Abdomen convex. Cornicles none. Tarsus provided with two claws. Winged forms unknown.

The species of this genus occurs in small scattered companies. They feed on the fine fibres of the roots of various grasses. They very commonly affect the nests of Formica flava.

Both Kaltenbach and Passerini consider the above- noted tubercle to be a true antennal joint. As it is very small, and is not articulated to the fifth joint, I do not count it such.

Koch remarks that the young have much resem- blance to Trama. They, however, may be distinguished from such by their more simple antennas and minute eyes.

The eyes of Trama are rather large than otherwise.

Forda formioaria, Heyd. Plate CXXVI.

Bhkoterus vacca, Hartig.

Forda formicaria, Heyd., Kalt., Koch, Pass.

Viviparous female*

Very variable as to size and colour. Large specimens measure —

Inch. Millimetres.

Length of body O'lOOxO'060 2-53 X 1*52. Antennse 0-040 1*01.

* Probably from/ero, which ordinarily makes latus, but irrregularly fordus, pregnant, or prolific ; thus forda vacca, &c. However, this genus is far less productive than most other kinds of Aphides

84 BRITISH APHIDES.

White, greenish, dull yellow, or dark green. Rather glossy. Long oval. Head blunt, smooth. Eyes black, prominent, but very small. Body ringed. Adult specimens often have a dark green stripe half way down the dorsum. Legs moderately long, pale brown. Antenna3 5-jointed, the last of which has a nail, which Kaltenbach counts as a joint. Rostrum stout, and reaches beyond the mid-body. Cornicles none.

Young examples are slimmer, and have longer antennse. Their rostra project beyond their tails.

Found in light sandy soils, and usually in ants' nests under the root-stocks of various grasses. The speci- mens figured were nesting in close proximity to a colony of Formica flava. In this instance I could trace no connection between the two nests, but there is abundant proof that Forda is a common companion of Ants. One difficulty of separating a particular species from another in such structures consists in the very mixed company that forms these assemblies. Thus in the same nest may be taken individuals belong- ing to the Aphis genera, Paracletus, Trama, Forda, and Endeis, and these insects are sometimes supplemented by representatives of Julus, Millepes, Oniscus, and a number of blind beetles.

When the full-fed individuals of Forda are gently pressed drops of a clear liquid exude from the dorsal pores, and this liquid probably is acceptable to these ants. This action, under the imaginative fancy of Hartig and of Kirby and Spence, is expanded into the likeness of milch kine, stabled underground for the winter use of the Ants.

Mr. J. Hardy kindly sent to me specimens of this insect from Berwickshire. They were smaller than the Haslemere specimens described above. They were found during the summer inhabiting the nests of Myrmica at the roots of JIolcus mollis.

Sir John Lubbock also forwarded to me specimens taken in February from similar situations at Becken- ham.

FORDA VIRIDANA. 85

Mr. "Walker obtained Forda from the roots of the sow-thistle, Sonchus oleraceus.

The habits of Forda formicaria are not apparently in all cases subterranean. I have taken them in April at Haslemere on the green leaves of Triticum repens just above the surface of the ground. I have represented such a modified habit in the plate above alluded to.

Koch figures and describes another species of this genus under the name Forda marginata. It is yellowish-white, and possibly may be the same insect as I figure, but the diagnosis agrees only in part.

Forda viridana, Bucldon. Plate CXXVII, figs. 1, 2.

Viviparous female.

Inch. Millimetres.

Size of the body 0*080 X 0*050 2*03x1*26.

Length of the antennas 0*035 0'88.

Oval, dull, pilose, and velvety. Colours variable, from rich chocolate-brown and mouse-brown to an emerald-green ; legs and antennae ginger-brown. Vertex setose. Eyes very small and inconspicuous. Thorax and abdomen much corrugated and domed ; nectaries none. Rostrum long, about three-fourths the length of the body. Tail blunt and carried slightly erect. Claws double, but often seen folded as if they were single.

Taken in small companies in Ants' nests covered by tufts of various grasses. It differs from the preceding species in several particulars, and chiefly in beiug smaller, more pilose, and deficient in the green dorsal stripe.

It occurs throughout May and June in the dry moors, near Wooler, in Northumberland.

Mr. James Hardy informs me the " malachite-green variety " may often be taken in quantity, nesting with Formica fidiginosa. This Aphis is particularly plentiful

86 BRITISH APHIDES.

under Aim flexuosa, at the end of May, in the above locality.

The brown insect is so commonly mixed with the green, and it agrees so well with it, except in colour, that I assume that the insects are identical. It is not uncommon under the tufts of Carex, on the moors round Alnwick, in Northumberland.

I have not met with it under the sand heaps in Surrey.

' Genus XXXIII.— TYCHEA,* Passerlni,

Antennas composed of five almost equal joints. Abdomen marginate. Eyes none. Legs short, with two small claws. Cornicles and tail none. Rostrum variable in length according to age. Winged forms unknown. Habitat very similar to the preceding species ; mostly being found at grass roots. Several species also are denizens of Ants' nests.

Passerini describes five species as inhabiting Italy, all of which, I believe, are inhabitants of Great Britain.

Tychea teivialis, Pass. Plate CXXYII, figs. 3, 4. Viviparous female.

	Inch.	Millimetres.
Size of body	0-050 X O040	1-27X1-01.
Length of antenna}	0-015	0-38.

Globose or ovate, rather flat, yellow or ochreous, smooth. Eyes none. Antenna) very short. The joints vary much in the different moults. In the full- grown insects the third joint is much the largest. In the fundatrix the antennas and rostrum are both

* If from Ivxiw, nanciscor, or asscquor, the allusion is not obvious.

TYCHEA SETUL0SA. 87

very sliort, the joints being much more equal in length.

Taken in Ants' nests, at Beckenham, under tufts of Poa, in November.

Passerini gives for food the roots of Triticum vidgare, Cynodon dactylon, Poa trivialis, Festuca duriuscula, fyc. He thinks that possibly Coccus Zece-maidis, of Leon Dufour, may be referred to this species ; and notes that the presumed single claw may probably be due to a mistaken diagnosis.*

Tychea setulosa, Pass. Plate CXXVII, figs. 5 — 8. Viviparous female.

Inch. Millimetres.

Size of body 0'075x 0-060 l-89xl'52.

Length of antennas 0'020 0*50.

Large, pearly white. Some are circular and domed. Vertex flat, head broad. Antennae 5- jointed, with a rounded button or nail. Third joint much the longest, but there is a tendency to a constriction, which might suggest an additional joint, and make Passerini' s phrase " articulis subasquilongis " more apposite. The whole insect is hirsute and tufted with setas, particu- larly as to the head and antennas. Eyes are merely red specks, and very minute. Legs short, the hinder pairs hardly protrude beyond the body. Tarsi with two claws which fold together so as often to appear but siugle. Rostrum very variable in length. The tip blackish. Cauda rounded. The younger or less developed forms greatly differ in proportion, and show only four antennal joints, with largely extended rostra. Some specimens are fuscous on the head and tail, and all are rather "mealy."

The larger insects contained from five to seven embryos. It is remarkable that the eyes and antennas * Vide ' Aphididce Italics,' p. 82.

88 BRITISH APHIDES.

of these yet unborn insects are quite as much developed as those of their mothers. It is to be noted also that in these insects the antenna? are disengaged or freed from the body before the other limbs (fig. 8).

Taken by Sir John Lubbock in ant-hills near Beck- enham, in April.

I kept several individuals alive in moist earth, together with three or four specimens of Formica fla vat for six weeks, without noticing any tendency to become pupae or to greatly vary in their general appearance. These insects partially change their colour and become darker by exposure to light.

In Italy the insects nestle at the roots of Oryza mon- tana.

Tychea setari^;, Pass. Plate CXXVIII, figs. 1 — 4. Viviparous female.

Inch. Millimetres.

Size of body 0-060x0-045 1-52x1*18

Length of antennas 0*030 076

Fundatrix short, oval, flat. Colour and texture like white kid leather, some with a faint tinge of green. Antennae very short, about one fourth the length of the body, 4-jointed, with a rounded wart. The third joint much the longest, and often showing a tendency to a constriction in the middle. Eyes very minute. Dorsum has ten or more dusky transverse bands, each terminating with a pore. Antennae, legs, and tail dusky brown. Rostrum short, reaching to the third coxae. Legs hardly project beyond the disc of the body. Cauda conical, sometimes with two or more crescentic marks above it.

After several moults the legs and antennae become much longer, the insect becomes rounder, and at the last moult an additional joint may be counted to the antennae. In all stages the body is finely pilose.

TYOHEA ERAGROSTIDIS. 89

The tarsi have two claws, but very commonly they are, like the preceding, so folded as to appear but one.

Taken in ant-hills at Beckenham.

The plate shows an insect just before moulting, when the old skin has separated from the new, yet it still envelops the insect itself.

The fundatrix attended by a few young may be taken as early as February.

Tychea erageostidis. Plate CXXYIII, figs. 5, 6.

Viviparous female.

Inch. Millimetres.

Size of body 0*050 X 0*040 1*26 X 1*01

Length of antennse 0*040 1*01

Ovoid or nearly circular, glabrous, whitish. Head broad, vertex flat and smooth. Antennal joints five, and almost equal. The fourth as small as the first, the fifth the longest, and furnished with a nail. Eyes and nectaries none. Abdomen domed and ringed. Legs stout and moderately long, claws double, but often folded together. Cauda obtuse. Rostrum about two -thirds the length of the body, but in the young it projects beyond the tail.

The queen Aphis or fundatrix is quite different in form, being shuttle-shaped. The antennas, rostrum, and legs are much less developed. Isolated points of red pigment mark the seat of the foetal eyes, which are only partially developed.

Taken in ant-hills at Beckenham, and also at the Cheviot, on the roots of Poa annua.

This insect feeds also on Panicum glaucum ; and apparently also is viviparous, on the lower exposed leaves of sweet vernal grass, Antlioxanthum odoratum.

90 BKITISU APHIDES.

Tyciiea phaseoli, Pass. Plate CXXVIII, figs. 7, 8. Vii'i parous female.

Inch. Millimetres.

Size of body 0*0G0 X 0*040 1*52 X l'Ol

Length of antennas 0*025 0*63

Large, globose or semi-globose. Opaque white. Slightly pubescent. Head flat and broad. Legs mode- rately long in the second brood, but short in the queen Aphis. The above measurement represents the size of the queen Aphis, which is blind. The brood proceeding from her are of different sizes according to their different conditions of development. The adults have 5-jointed antennas, the fifth joint being rather the longest, and the fourth the shortest. Minute pigmentary spots represent the eyes in the full grown insects.

Sometimes this species is numerous at the roots of the scarlet-runner, Phaseolus coccineus, from which the above specimens were taken at Walthamstow. It occurs also upon the French-bean, Phaseolus vulgaris, and also upon the roots of Brassica, Euphorbia, and Amaranthus.

Genus XXXIV.— ENDEIS, Koch*

MlNENLAUS.

Rostrum moderately long. Antennas 5-jointed. The first two and the fourth nearly equal ; the third the longest; the fifth ends with a nail. Eyes very small, but prominent. Body cycloid or else pear- shaped. Cauda obtuse and bristly. Legs very short; tarsi and claws as in Tychea.

Koch remarks thai, as far as his knowledge went, his two species, Endeis h, lla and B. rosea, lived in small companies about the roots of wheat in September.

* From IvSu'ic, deficient.

ENDEIS PELLUCIDA. 91

The proportions of the antennal joints as given above are slightly different from those given by Koch ; but I prefer to group the following three new species under Endeis rather than form another genus out of the somewhat obscure characters furnished by the materials at hand.

Endeis formioina, Bucldon. Plate CXXIX,figs. 1 and 3. Viviparous female.

Inch. Millimetres.

Size of body 0-045x0-040 M4xl'01

Length of antennas 0*01 5 0*38.

Opaque white, globose, smooth, somewhat mealy; narrow towards the head. Abdomen ringed. Head with two brown patches on the occiput. Eyes brown and very minute. Antennas with five nearly equal joints. Legs and antennas brown. Rostrum short and stout. Tarsi with two claws.

Taken by Mr. James Hardy under the dry stones formed from the porphyritic rocks on the Cheviot. In May they were numerous in the ant-hills under roots of Garex dioica. They mostly affected those nests of Formica umbrina which were located on the dry slopes.

Endeis pellucida, Bucldon. Plate OXXIX, figs. 2 and 4. Viviparous female.

	Inch.	Millimetres.
Size of body	0-035x0-030	0-88x0-76
Length of antennas	0-015	0-38

Body very broad behind, narrowing to the head ; pale greenish or opaque white ; much ringed, pilose. Head stained reddish. Eyes none. Tail obtuse and

92 BRITISH APHIDES.

rounded. Antennas with five nearly equal joints. Legs pale and short. Rostrum stout and short.

Taken under tufts of grass, such as Poa annua, covering the nests of ants, and exactly in the same situations as noted in the preceding species. They were found at Beckenham during February.

Endeis carnosa, Bucldon. Plate CXXIX, figs. 5 — 8.

Endeis bella9 Koch ?

Viviparous female.

	Inch.	Millimetres.
Size of body	0-030x0-025	0-76x0-63
Length of antennas	0-010	0-25

Body circular, much domed. Uniformly whitish- yellow, flesh-coloured, or pink. Brown at the tail. Antennas short, with five nearly equal joints and the usual tubercle. With age the third joint lengthens. Head very broad, with a brown dot on the vertex. Eyes very small and brown. Legs exceedingly short, hardly produced beyond the circumference of the body. Cornicles none. Cauda, viewed from under- neath, cylindrical and truncated. Tarsi with two minute claws. The whole insect is finely pilose. On the vertex the hairs are discoid and capitate.

Captured in February in an Ant's nest with several other Aphides, including Trama and Paracletus. They had many young wood-lice (Oniscus) in their company. Taken at Beckenham.

Genus XXXV.— RHIZOBIUS,* Burm.

Rostrum very short, rises between the first coxas. Antennas very short, five-jointed, the first four joints

* From /J«£iW, a rootlet; /3u5w, I live.

EHIZOBIUS P02E. 98

nearly equal in length. Eyes inconspicuous. Body more or less furnished with woolly flocks. No necta- ries nor tail. Legs short, tarsi terminated by a single claw. Winged forms unknown. Neither males, females, nor true ova have been yet described.

Passerini describes Rkizobius menthce and B. sonchi. The latter insect is found at the roots of various plants, as Achillea, Sonchus, Stachys, Galeopsis, and Cichorium. I have not been able to identify these species in England. Passerini makes the antennas six-jointed. The characters, however, are very incon- stant.

Rhizobius poj;, Buchton. Plate OXXIX, figs. 9 — 14. Viviparous female.

	Inch.	Millimetres,
Size of body	0-075x0-035	1-89 X 0-8!
Length of antennas	0-010	0-25

Long oval (in the spring individual fusiform). Colour dull ochreous yellow. Eyes, antennas, legs, and two occipital longitudinal bands, brown. Antennas very short, varying according to age ; from three to five joints and a nail. Abdomen deeply ringed with numerous dark spots, ranged in transverse rows across the dorsum, from which woolly matter sparsely proceeds. A pale line passes from the vertex down the whole back. Eyes very minute. Legs very short ; the coxas being placed well forward on the sternum. The tarsus is armed by a single claw ; but, as this has two bristles, a high magnifying power is necessary to show its single character. Rostrum very short, but this increases in length by age to the third coxas.

Yery numerous at the roots of Boa annua on the Northumberland moors. On moving the soil the white tufts of cotton-like fibre, spun from the dorsal pores, betray the presence of these insects. Sometimes

94 BEITISH APHIDES.

the Aphides are solitary, at other times small com- panies of eight or nine may be found herding to- gether. They occur from May to October, and then probably they burrow deeper and evade observation.

Occasionally the antennal joints differ in number on the two sides, thus development would seem to go on at uneven rates.

APHIDES IN THEIR ECONOMICAL RELATIONS TO ANTS.

The subject of favouritism amongst insects affords one of the most curious phases of their economy. At the same time the matter is one of the most obscure. It has exercised the imagination and ingenuity of Entomologists for more than two hundred years, and at present hypothesis, more or less probable, is put forward as to how far mere utility or intelligence, or even a quasi-civilisation, has produced such peculiar conditions of life.

These habits, which may be styled Sycophancy* or Paracletism,f differ from parasitism ; for one insect does not prey on the other, but is nursed and cherished as a pet. The habit comes out most markedly amongst what may be considered the most intelligent insect- orders, like the Hymenoptera.

The wars, raids, slave-driving, huntings, stratagems, and singular architecture of this order has been de- scribed by many, but Sycophancy or, better perhaps, Paracletism would suggest a peculiar refinement beyond mere utility.

The handsome apathetic humble-bees are destitute of corbiculas or pollen-baskets, usually developed on the thighs of the Apidje. These large Bombidae apparently neither work or gather honey. Have they become degraded, and have they lost at the same time, by disuse, the natural apparatus conducive to

* From o-vKo<pdvTt)s, a parasite, perhaps one who informed against persons plundering sacred fig-trees, from gvkov and <paivu. t From irapa<\t)Tog, a patron or comforter.

96 BRITISH APHIDES.

work, whilst being fed and caressed by their indus- trious but less showy hosts ?

Mr. Frederick Smith has shown how some of our active industrious bees (Andrenidee) tolerate the presence, and, indeed, seem to have friendly relations with the maurauding and destructive bee-wasps (Nomada), which are permitted to enter their sand burrows, and steal the food stored for the use of the young Andrena.*

Prof. Westwood some years ago showed how For- mica flava stores certain blind beetles, as Clavager Duvallii, in their nests ; and solely, it would appear to him, for the sake of feeding on a gummy secretion which exudes from the bristles at the termination of their elytra. f

More recently Markel counted no less than fifty separate species of Coleoptera in the Ants' nests of Switzerland, many of which were quite blind, their eyes becoming obsolete and useless in the darkness of their subterranean dwellings.

M. Lespes regards these beetles as real domestic animals, and he has recorded several curious observa- tions with reference to their economy, and that of the ants with which they consort. J

It is remarkable that hitherto Clavager Duvallii has only been discovered in the nests of Latins niger. But nests of this ant do not always contain such beetles; and if the last are forcibly introduced they usually are immediately killed and eaten by the inhabitants. The suggestion has been accordingly made, that some communities of Lasius are not so far advanced in civilisation as others, and that they have not yet developed the hospitable virtues. They are still, in short, barbarians.

# Vide Introduction to the British Apidsc, ' Cat. Brit. Hymenop. Brit. Museum.' by F. Smith, pt. 1, p. 210.

f Westwood's ' Int. to Modern Class, of Insects,' i, p. 176, and ii, p. 234.

X Vide Denny and Lespes, ' Annals and Ma£. Nat. History, ' vol. i, 2nd ser.. ]'. 240 ; also 'Ann. des Scien. Natur.,' 18G3.

APHIDES AND ANTS. 97

Sir Joseph Hooker and Prof. Tyndall have each urged the injury done to discovery by the divorce of imagination from science. " Observation, enthusiasm, and imagination — these three are the prime factors to which is due all excellence in science and art." Doubtless a vivid and educated perception will greatly help a successful generalisation, and often present a working platform for subsequent experiment ; but, on the other hand, the most correct idea may suffer by an expansion under the exuberant fancy of those who love marvels.

The fact that Aphides are most friendly to such dissimilar insects as Ants has been long known. Goedart, in Reamuer's time, allowed his fancy to run into imaginary conversations between them, relating to such subjects as warning each other against their foes and the like.

From a similar fancy it is, that the term " vaccse," playfully given by Linneus to those Aphides which yielded their sweet secretions to the solicitation of ants, became " milch cows ; " and the " thrumming " of the ant's antennae on the sides of the abdomen has been since likened to the action of the fingers in ordinary milking !

Even Morren saw certain curious analogies between Aphides and Mammifers, and considered that the young Aphides were nourished by the quasi-milk furnished by the nectaries of its mother.

From Pierre Huber (the son of the historian of bees) we learn that certain continental Ants enclose portions of leaves, largely tenanted by Aphides, in a kind of wall constructed of mud. This enclosure soon afterwards became, in imagination, a paddock for the above milch cows. Again, the cavities below the roots of grasses near ant-hills, in which sub- terranean Aphides feed, are likened to stables or cattle-lairs.

Huber the younger was aware of the incredulity of his contemporaries ; and that by them his discoveries

VOL. iv. 7

98 BRITISH AMIDES.

were looked on as more or less romantic tales. Accordingly, in the commencement of his history of the indigenous ants of Geneva he affirms that he has neither been led aside by a fertile imagination, nor by a love of the marvellous.*

In this history Huber shows the way in which certain ants construct covered passages of earth or other materials through which they can, in all weathers, visit their Aphides, which live on the plants growing on the surface above, at short distances from their nests. I cannot myself prove that any of our British ants form such curious corridors ; but Huber found in the neighbourhood of Geneva that a red ant constructed spherical lodgments over such thistle heads as were loaded with Aphides. In these chambers, which were formed of mud, the ants securely drew their sustenance from the plant-lice. On one occasion he discovered an earthern cylinder, 2 J inches by 1^ inch in size, which had been built near the root of a thistle, and the cylinder contained many Aphides and their attendant ants. But these tunnels, it appears, are not confined to the surface of the ground ; for Huber found one five feet above the level of the soil, which enclosed a small branch of a poplar tree. The ants travelled through the decayed and hollow stem and emerged at a junction of this branch, immediately close to which an opening appeared. This was the entrance to a •' blackish tunnel," within which they could feed without disturbance. Numerous such instances are related by Huber; and he adds that some covered ways were fabricated out of decayed wood instead of clay.

Huber' s words are remarkable and worthy of quota- tion ; since they state as facts that which is very diffi- cult to realise without personal proof. f

rim,' iIuUt (the younger), 'Recherches but lea moaurs des fourmis indigenes,' Paris: also a translation of the Bame, by Johnson, ' Natural History of Ants,' London, 1" f Pierre Huber, 1. c, ' Traml./ Johnson, pp. 228—231.

APHIDES AND ANTS. 99

He says, " Four or five species of ants keep pucerons in their abode ; but less constantly, and in much smaller numbers than the yellow ant ; as they obtain a portion of their subsistence from those (Aphides ?) inhabiting trees. There are some who reach the branches loaded with these insects, under a covered way of earth lead- ing directly from their nest. Here the ants are as well furnished with food as if they kept the pucerons in their own dwellings. As often as they wish to bring these insects to their nests, they can accomplish it without the knowledge of other ants, and without incurring any risk. . . ." "The turf ant . which from its small size (being only half a line in length) may be called the microscopic ant, finds pucerons proportional to its own size. They are of a white colour, and but a little larger than the ant itself. Pucerons are thus the domestic animals of the ants."

Again in another place Huber says that the Ants transport the Aphides to their nests, rather than the Aphides come to the nests of their own accord. In- deed, he thinks that the Ants make systematic searches for Aphides amongst their galleries, which sometimes extend to perhaps thirty or forty feet under the soil. Subsequently the captives are brought into the imme- diate vicinity of the nests of their captors, and located under the domes of the same. Huber says, " I have seldom discovered Aphides under the ground, without their being surrounded by yellow ants, who arrive at their haunts by the subterranean passages, and who probably convey the Aphides to their nests in the autumn."

Even here wonders do not cease, for he discovered that ants collect the ova of Aphides, and store them with every precaution to preserve their vitality ; and that on the return of spring they place them in suitable conditions for hatching the young.

It is not easy to see how the Aphis eggs can im- prove in condition by all the treatment they are said

100 BRTTISH APHIDES.

to undergo when cared for by the ants. They are repeatedly licked over, and lubricated with a glutinous fluid, and treated as if they were eggs of their own species.

Huber discovered that disputes often occur amongst ants, as to the quiet possession of their pucerons. He says that when the ants of one nest succeed in entering the habitations of their neighbours, they purloin the insects, which again are sometimes triumphantly recovered by their original proprietors.

Sir John Lubbock has also made some interesting remarks on this subject of storing Aphis eggs, which bear out in great measure the observations of Huber. He finds that the English Lasius flavus collect their eggs and store them for perhaps six months of winter. In the spring these eggs hatch, and he noticed that whilst some of the Aphides issued of themselves from the ground and searched for their food ; the others were taken by the ants and placed on suitable plants whereon they throve.

I have been unable to examine these Aphides, or learn their species. They are described as differing from the more common subterranean forms ; and that generally they affect the axils of the common daisy, Bellis per&rmis. " The ants build up a wall of earth round and over them ; " presumably for the same purposes as stated by Huber, viz. for ant- runs.

It is by no means easy to assign good reasons for this storage of eggs. Inclemency of winter would seem to have little to do with it ; for the eggs, it is well known, will stand extreme cold ; and they are covered by a natural varnish which is impervious to rain.

This opinion as to their hardihood does not however accord with Sir John Lubbock's explanation, for he Bays, "The eggs do not remain where they are laid, where they would be exposed to the severity of the weather.

APHIDES AND ANTS. 101

Gould in early days noted these black eggs and mistook them for the female eggs of the ants.

It was not till March, 1880, that the hatching of these eggs was witnessed by Sir J. Lubbock who saw the process ; and the produce of these eggs differed entirely from the subterranean species often found in such situations.

" Near one of my nests of Lasius flavus, in which I had placed some of the eggs in question, was a glass containing living specimens of several species of plants commonly found on or around ants' nests. To these some of the young Aphides were brought by the ants. Shortly afterwards I observed on a plant of daisy, in the axils of the leaves, some small Aphides very much resembling those from my nest, though we had not actually traced them continuously. They seemed thriving and remained stationary on the daisy. Moreover, whether they had sprung from the black eggs or not, the ants evidently valued them, for they built up a wall of earth round and over them. So things remained throughout the summer ; but on October 9th I found that the Aphides had laid some eggs exactly resembling those found in the ant's nest ; and on examining daisy plants from outside, I found on many of them similar Aphides and more or less of the same eggs. I confessed these observations sur- prised me very much." ..." Here are Aphides not living in the ant's nest, but outside on the leaf stalks of plants. The eggs are laid early in October on the food plant of the insect. They are of no direct use to the ants, yet they are not left where they are laid, where they would be exposed to the severity of the weather and to innumerable dangers, but brought into their nests by the ants, and tended by them with the utmost care through the long winter months, until the following March, when the young ones are brought out and again placed on the young shoots of the daisy. This seems to me a most remarkable case of prudence. Our ants may not perhaps lay up food for the winter,

102 BRITISH APHIDES.

but they do more, for they keep during six months the eggs which will enable them to procure food during the following summer.*

The veteran entomologists Kirby and Spence, who noted also the occurrence of Aphides in ant-hills, decidedly endorse the theory that " they are a provision to sustain the lives of their captors during their half- torpid condition until early spring. By an admirable provision these Aphides awake out of their torpor and at the same period the ants also awake. "f

Again they say, " Formica flava receives almost the whole nutriment, both of themselves and their larvas, from Aphides " ; and that the prosperity and wealth of communities are in proportion to the number of their cattle. Here they follow Huber, who says that an ants' nest is more or less rich according to its stock of what he calls their " cows and goats." $

As before noticed, imagination may not be banished from science, yet caution is needed lest science should drift into fancy, or foster a more popular taste for description. Entomology is peculiarly liable to suffer from a florid style in the hands of those who write to amuse as well as to inform their readers.

I would ask attention to the following considera- tions before committing ourselves to any theory of Paracletism.

1. Many species of ants are partial to honey and the sweet secretions of insects, but it has not yet been satisfactorily shown that any Ant is dependent on Aphides for its exclusive support.

2. Some species of Aphis feed on roots which often intersect ant-nests, but most ant-hills are destitute of Aphides.

3. The roots of many grasses growing in light soils

* Sir J. Lubbock, 'Journ. Lin. Soc.,' vol. xiv, p. 610; and 1880, vol. xv. p. 182.

f Kirby and Spence, ' Introd. to Entom.,' vol. ii, p. 349 (1843).

X Germar, ' Mag. der Entom.,' iii, t. 2; also vide Boisier do Sauvagcs, ' Journ. de Physique,' torn, i, p. l'J5, " On the Relations between Ants and Aphides.

APHIDES AND ANTS. 103

are attacked by several species of Aphis. Ants do choose such localities for their nests, In such cases they are on the best of terms with the Aphides ; but the latter are no more necessary to their economy than the blind Coleoptera, Myriapoda, and the like, which are commonly found intermixed with them.

4. Many aerial Aphides are visited by ants whilst feeding on the sap of plants. Honeydew is secreted out of this sap by organs connected with their nectaries. Captive Aphides, condemned to underground life, are cut off from their usual food, and it is presumed they can no longer secrete honeydew.

Huber's cattle-lair theory is, therefore, unsatisfac- tory. If Aphides are imprisoned after marauding expeditions, it must be for a different purpose than for collecting food.

It will be unwise to put limits to the peculiar phases of insect economy. Extraordinary ingenuity and unexpected habits are continually pressing on the observation of the entomologist. Perhaps the only safe conclusion arrived at with reference to Aphis and Formica is, that the latter is a considerable sugar con- sumer, and that like Man, it also is a fosterer of pets and favourites.

In the tropical parts of India and Brazil, where Aphides do not exist except on the high table lands, ants show their appetite for sweets by thrumming the sides of the larvae of certain species of Cercopis and Menebracis (Coccidaa). In England I have often noticed their resort to some of our Psyllida for the same purpose.

It is not a little remarkable that the friendly rela- tions between Aphis and Formica have been of a very ancient date. There are unmistakable evidences that in the Middle Tertiary ages, when the Hymenoptera were so largely represented by ants (far more so than in modern times), the then existing Aphides were as much frequented by them for their secretions as now.

The Rhizobiinaa are all root-feeders; yet, as there

10-A BEITISH APHIDES.

are other subterranean species not included in this group, it may be useful to give a list of such, most of which are noted in this Monograph. It is probable that some of these, like Pemphigus and Phylloxera, have aerial forms.

List of Aphididce which are known to effect part of their metamorphosis underground.

Siphonophora tussilaginis (?).

Aphis fat farce, A. lappce, Koch; A. intybi, Koch; A. plant aginis, Schr. ; A. ranunculi, Kalt. ; A. suiter- ranea ; A. symphiti, Sch. ; A. terricola, Rond.

Trama troglodytes.

Paracletus cimiciformis.

Schizoneura fodiens, S. venusta, Pass.

Pemphigus Boyeri, Pass. ; P. cerulescens, Pass. ; P. fuscifrons, P. lactucarius, P. ranunculi, Pass.

Forda formicaria, F. viridana.

Tychea eragrostidis, T.phaseoli, T. setarice, T. setulosa, T. trhialls.

Endeis carnosa, E. formicina, E. pellucida.

Bhizohius pilosellce, B. sonchi, B. mcnthce, B. sub- terranea, Kalt. ; B. poce.

Phylloxera vastatrix.

ADDENDUM.

Subsequent to the publication of my first volume, several large Aphides were kindly sent to me from Scotland in the summer of 1878 by Professor Trail, of Aberdeen. They were found feeding on Buhus fruticosa, and they showed all the characters of Siphonophora.

Unfortunately no winged forms could be secured, which would have permitted a more satisfactory diagnosis. The antenna) and legs of these specimens are remarkably long, the cornicles are more cylindrical than in 8. rubi proper, and the body is hirsute.

The most striking character is their bright rufous

siphonophora rubi, var. RUFA. 105

colour, varied on the body with obscure bands and dots of rich brown. These differences are sufficient, I think, to mark the insect as a good variety of 8. rubi, which in England is always, I believe, of a lively green colour.

The measurements are as follows :

Siphonophora rubi, var. rufa. Plate CXXX, fig. 1. Apterous female.

Inch. Millimetres.

Size of body 0-090x040 2-28xl'01

Length of antennas 0'160 4*06

cornicles ' 0*040 1*01

Numerous examples of Aphides mounted in Canada balsam by the late Mr. F. Walker, have at different times come into my possession. Most of them unfor- tunately are unnamed by him, but amongst those labelled I find specimens of pupae with well-developed wing-cases belonging to the genera Forda and Trama.

Mr. Walker, in his ' Catalogue of Homoptera in the British Museum, states that the species, " Trama troglodytes and Paracletus cimiciformis occasionally but rarely assume wings."

In my diagnosis, vol. Ill, p. 67, I omitted to make drawings of these pupge. I now figure them, PI. CXXX, fig. 4, for reference, but upon Mr. Walker's authority, for I have never met with the alate forms, and I believe others also have been unsuccessful in the search.

On the same Plate CXXX, fig. 2, I depict the imago of Apliis subterranea, the living forms of which up to this time have escaped my notice. I have several slides containing the winged forms of this Aphis mounted for the microscope by the late Mr. F. Walker.

106 BRITISH APHIDES.

I.— REPRODUCTION OF APHIDES.

" If this Essaye were worthy judged of, it might not greatly please the common and vulgar spirit, and as little the singular and excellent. The first will understand but little of it, the latter overmuch." — Michael dc Montaigne, cap. liv.

1. GENERAL OBSERVATIONS.

A geeat part of the interest attaching to the Aphis family is connected with their double mode of repro- duction ; a process represented by the terms gamic and a-gamic. It is true that when once this unexpected fact was substantiated by early biologists, it was dis- covered that the non-intervention of the male was of more frequent occurrence amongst the lower animals than was at first recognised. The discovery, indeed, was not quite so new as was at first assumed.

The philosophic Aristotle appears to have had some indistinct notion of a like phenomenon ; and he seems to suggest something akin to non-impregnation in his remarks on the development of the egg of the drone or male bee.

\\\ Earvey commented upon and corrected the opinions of Aristotle and Fabricius, and declared against spontaneous generation. He did this very decidedly in the words " Omnia omnino animalia etiam vivipara, atque hominem adeo ipsum, ex ovo progigni;" and again later, " Cuncta animalia quodum modo ex ovo nasci affirmavimus."

In another passage, however, he seems to admit the current doctrine of production of worms by putre- faction, as an exception.*

* Vide W. Harvey, 'Omnia opera* 4to, 1766, p. 182, and p. 482. Also article " Harvey," ' Encyclopaedia Britanica.'

EEPRODUCTION OP APHIDES. 107

Even before the time of Reaumur's and Bonnet's discoveries it had been asserted that the unimpreg- nated egg of some Papilionidas had proved fertile, but such novel observations met with but scant attention ; firstly, perhaps, from incredulity as to the fact, and secondly, from a notion that such was contrary to all experience.

Here the subject seems to have rested for nearly one hundred years. The phenomenon of multiplica- tion by fission observed by Trembley in the fresh- water Hydra was too recent and peculiar to cause the naturalists of his day to infer analogous processes in Insects. Still an attempt towards an explanation was made with reference to Aphides both by Leuwenhoeck and Cestoni, who considered that these insects were hermaphrodite; and this belief accorded with the views of the best zoologists of that day.

Bonnet substituted another explanation, and argued that the chief difference between the viviparous and oviparous female consisted in the more or less perfect development of the two forms. According to his view, the conjunction of the male gave to the germ that which the mother, on account of her incomplete development, was unable to supply to her progeny. Abundance of food, and a high temperature, he thought, produced the first form ; cold and insufficient food in autumn caused the appearance of the egg- laying female, viz. the second form.*

Trembley attacked the subject differently. He con- sidered that the influence of the male in autumn transmitted itself throughout the whole generation of females of the following year ; and this view, more or less modified, was accepted by Dutrochet, and by Kirby and Spence, who all rejected the hypothesis of hermaphroditism.

Reproduction amongst animals may occur through several processes, all of which are in a measure analogous to the propagation of vegetables. Amongst

* Bonnet, ' Considerations sur les corps organises,' t. ii, 1776.

10S BRITISH APHIDES.

the Protozoa multiplication takes place by fission or separation into two or more individuals ; or by budding or gemmation, where a separation of the smaller indi- vidual from its parent is preceded by a growth in the lesser form. According to Prof. Balfour, no essential portion of the parent is removed during this process. A portion of a nucleus may separate either externally or internally from the protoplasm. The spores of animals may break up into very numerous parts, all of which may materially differ from the form of their parents. In the Infusoria such spores are often furnished with a vibratile lash or flagellum, by which they progress through the water or other fluids in which they live.

Even in the lowest vegetable forms a conjugation of cells seems to be the condition of a renewed vitality; though the fact is remarkable, that the conjugation of two or more individuals does not invariably lead to immediate reproduction. Such conjugation, however, probably conduces to a fresh vigour in the animal, and conduces to a differentiation which checks the evils of self -fertilisation.

In the Metazoa both sexual and non-sexual pheno- mena obtain. The first consists of the fusion of the ovum and the spermatozoon, attended by a subsequent division of the compound cell. Development hero mostly results in the production of forms similar to the parents.

La Hire, perhaps, was the first to observe the process of egg-layingin Aphis ; and al fclie same time he demon- strated that both viviparism and oviparism might go on side by side in the same family of insects.

Prof. Owen, in more recent times, revived the theory originally started, it is believed, by Dutrochct, in a lecture delivered to the members of the Royal Institu- tion of London. After giving an interesting definition of the collective individual, Prof. Owen stated thai there was mi scientific diiHculty in conceiving the efficacy of the male influence as shown by Aphis, notwith-

REPKODTJCTION OF APHIDES. 109

standing the wonderful dilution of energy which must occur throughout the countless components of the generations following.*

The propositions made by the Swedish naturalist, De Greer, in 1773, have been already noted. f He agreed with Bonnet in the modifying action of food and climate, and thought it highly probable that, if Aphides should be discovered in tropical countries, they would be exclusively viviparous. Leydig also entertained very similar views on this point.

KyberJ: made experiments on the effects of food and temperature, and he came to the conclusion, which is now untenable, that such influence was sufficient to change the apterous oviparous female into the vivi- parous female ; and this error seems to have been shared by the French anatomist, Charles Morren.

The close similitude of form of the ovarian chambers of the true female and the chambers which develop the germs from the viviparous individual doubtless misled both these observers. The latter observer made good dissections of the reproductive organs of both male and female Aphides ; but he failed to note the significant absence of a spermatheca in the vivi- parous female. Such a knowledge also would have saved Bonnet from the error of supposing that vivi- parous germs and mature ova were often present in the same insect.

Considering the comparatively early date of Morren' s memoir on the anatomy of Puceron du pecher, his remarks and discussions are very suggestive. He says it is very difficult to bring one's mind to accept the hypothesis, that Aphides, up to the eleventh generation, are the results of the fecundation of their ancestors anterior to the first of the series. " The eleventh generation," he says, " does not exist at the moment of fecundation of the first." " He would

* Prof. Owen's lecture, ' Proc. Roy. Instit./ vol. i, p. 9.

f Vol. i, p. 55.

X Kyber, ' Germar's Mag. der Entomol.,' 1815.

110 BRITISH &HIDES.

prefer to acknowledge his ignorance, rather than give an opinion in such a labyrinth." "S' il fallait une expli- cation a toute force, j'admettrais que la generation se fait ici comme chez quelques Entozoaires, par indivi- dualization d'un tissue precedemment organise."

He says that the generation on that account is not spontaneous, for such a generation ought to be the product of an organised being, "de toutes pieces," when the inorganic elements unite to produce an animal or plant. " This has never taken place, and is impos- sible." Again he continues : " La generation equi- voque " is that when the tissues previously organised by a being provided with life individualise themselves, that is to say, separate themselves from the common mass, and still participate in the dynamic state of the mass after this separation for its own benefit. Thus it is that a tissue produces an Entozoon. It is a continued life.

He continues : " But suppose that the life has a sufficient energy to impress itself on the tissue which individualises itself .... in such a case you have the generation of the Aphis. This energy is lost at the end of certain generations; and then a new impulse becomes necessary ; and this impulse comes from the male."*"

It is obvious that such a process amounts to a non-sexual " budding," now so commonly known to prevail amongst the lower animals.

In another place Morren assigns the origin of the non-sexual viviparous Aphis to a body — " d'ocuf forme de globules reunis, et sans enveloppe apercevable."

M. Balbiani remarks, it will be more rational to compare this body either to a true ovum or else to a ^•(•l'lniiiniivc sac, after the example of other naturalists.

Morphologically ov:i may be regarded as buds, with

this special difference that the latter arc incapable of

fertilisation. If this difference did not exist, some,

like Leuckart, might assert that in certain kinds of

* Ch. Morren, " Puceron du pecher," ' Ann. des Sc Nat.,' p. 65, 1836.

KEPKODUCTION OL' APHIDES. Ill

animals the males do not exist. Von Siebold even surmised that in certain species a process of elimina- tion was in action as regards the males, and that such a process finally would result in a strict partheno- genetic reproduction of such species.

But it will be very unsafe to dogmatize on negative evidence as to the non-existence of males. The male of the Bntomostracan Apus was long unknown, but in 1858 it was discovered by Kozubouski. Still, this sex occurs so very infrequently, that not one could be found amongst the 5790 individuals said to have been examined by Siebold. Again, Sir John Lubbock examined 193 specimens of Apus cancriformis taken from a pond near Krakow; and amongst these he discovered but one single male. The fact seems to become more and more patent, that as we become better acquainted with the metamorphoses of the lower animals, and the very different larval aspect they can assume, such anomalies will disappear. Under the present conditions of life a conjuncture of male and female cells seems to be all but imperative for the renewal of life-cycles.

The absence of a spermatheca in some low aquatic forms might argue the non-existence of males; but here possibly a large volume of the male element, diffusing itself through the surrounding water, may ensure action on the ova, in a manner similar to the milting of fish, and make this sperm receptacle unnecessary.

In 1856 Yon Siebold gave a rude shock to the prevailing current opinion ; founded on Harvey's dictum " ornne vivum ex ovo," * by showing that a true parthenogenesis obtaius amongst moths and bees. Before his time it had been almost uniformly assumed that without the action of the spermatozoon on the ovum no fertilisation could occur.

In 1857 the same biologist demonstrated that the queen bee exhausts her store of sperm in fertilising

* This aphorism, usually attributed to Harvey, appears to be a contraction of bis words, already quoted.

112 BRITISH APHIDES.

eggs, which uniformly under its influence produce female forms. In other words, the drone or male bee always hatches out from an unfertilised egg. At first this seemed to be a grand fact to generalize upon ; but shortly afterwards it was satisfactorily proved, that in some other families of insects the converse was true; namely, that unfertilised eggs produced entire female broods to the exclusion of all males. This last peculiarity is true also in the crustacean Apus cancriformis.

Yon Siebold's very important researches on the small social wasps, Polistes gallica and P. diadema, must be fresh in the memory of many. His observations go to prove that, whilst the impregnated queen wasp produces eggs, furnishing first the female and then the male forms, the virgin queen can alone produce the latter. He also states that the parthenogenetic pro- geny of the leaf-wasp, Nematus ventricosus, is male.*

It really would appear, that mere speciality of sex has but little to do with impregnation or otherwise, for the Lepidopterous genera Psyche and Selenobia are stated to furnish by impregnation females exclu- sively in the first case, and almost exclusively in the second.

M. H. Weijenbergh made some interesting experi- ments on the same subject with reference to the un- impregnated eggs of the Lepidopterous insect Liparis dispar. Of the caterpillars which hatched out in the following spring he destroyed all the males. The imagoes appeared in August from the remaining eggs. Although these were all virgins they produced eggs which hatched in the next April, just like the preceding batch. These unimpregnated broods appeared for three consecutive years, though with diminished vitality. Finally they ceased to hatch, inasmuch as the eggs dried up all together. f

* 'Beitrage but Parthenogenesis der Arthropoden,' von C. Th. von Siebold.

f 'Archives N< M rlandaises,' published by the Soc. Hollandai6e des Sciences a Havleem, 1870. Also r/'</. b summary of this subject by Prof. Ray Lankester, ' Nature,' October, 1872, p. ^23.

REPRODUCTION OP APHIDES. 113

Unexpectedly, the males and the females were nearly equally numerous in all the broods experimented upon.

It may not be considered out of place here slightly to remark on the ephippial eggs of Daphnia, which have been at different times described by Dr. Baird, Sir J. Lubbock, and others.

Dr. Baird showed, as regard the water-flea, Daphnia (which sometimes occurs in such quantity in our ponds as to colour the water red), that a single copulation is sufficient to fertilise the female through life ; and Jurine thought that this fertilisation might extend even through fifteen generations.*

Two kind of ova are developed in Daphnia.

The ordinary ova are transferred from the ovary into a chamber near the back ; but the extraordinary ova have their development in a kind of saddle attached to the little crustacean, whence the term ephippial ovum.

They are also called by some authors hybernating or winter eggs. From the impermeable integuments which encase them, they can resist either a dry heat or a considerable cold without loss of vitality. As these eggs, however, are often formed during the heat of summer, the term hybernating eggs, perhaps, is not a very happy one.

Von Siebold showed that these ephippial eggs contain no germinal vesicle ; and Dr. Burnett main- tained that they are instances of " internal gemmi- parity," and just so he regarded the phenomenon of the agamic reproduction of Aphis to be a process of internal budding.

Prof. Allman likewise agrees that these winter eggs, which he styles statoblasts, are not true eggs ; but separate granules, wThich contain no germinal matter, vesicle, nor macula ; and that they do not undergo segmentation. Ephippial eggs, Dr. Allman says, may even be budded from the stomach-walls of an animal. Again, Prof. Huxley similarly shows a dissimilarity

* W. Baird, ' Brit. Entomost.,' Bay Soc, 1849, p. 80. VOL. IV. 8

114 BRITISH APHIDES.

between the two bodies. The ephippial egg is usually twice the size of the true ovum, and is in effect an aggregation of cells ; in fact, parts, or sometimes the whole of the ovary is encased in a shell with its membranes, so as to simulate true ova.

To summarise the foregoing remarks ; two varieties of ova may be characterised. The first represents the ovum proper, which is the direct product of the sexual process. The second is altogether non-sexual, and is known by a variety of terms, as statoblast, ephippial egg, pseudovum, winter egg, gemma, bud-germ, or spore.

All recent research points to the belief that ova are the means finally resorted to by nature for specific maintenance ; and that for reproduction, a conjugation of simple cells of different potentiality is a constant phenomenon.

In almost the identical words of Dr. Allen Thomson,* ''Multiplication entirely without any known sexes has been remarked in very few instances. In others, the non- sexual process of generation gives rise eventually to sexes which arc simply the repetition of the parent. If a nou-sexual multiplication occurs, it takes place during the incomplete condition of the animal."

A remark by Prof. E. Kay Lankester may be here added, as it refers to the eggs of the little Ento- mostracan Apus, which " escape from follicles as a matter of course, and pass along the canal leading from it to a primary branch of the ovarian tube, and then two or three eggs fuse into one mass, around which a shell is accreted, and this forms the actual

egg"

In Pyrosoma five embryos may come from one egg ; but this is the converse of the foregoing. Prof. Huxley remarks to me thai this is really a process of budding.

The unimpregnated ovum of the hen, and even of

* Dr. Allen Thomson, " Ovum," * Todd's Cycl. of Anat.' Sup., pp. 33, 37, 137.

REPKODUCTION OF APHIDES. 115

the sow, has been said to undergo something like a segmentation. But as one swallow does not make a summer, so great caution must be exercised before any idea of parthenogenesis can be extended to these higher animals, based upon observations so few in number.

Space does not permit here to enter on the vexed question as to the difference between animal buds and true and fictitious ova. The subject has been already- treated by Yon Siebold, Leydig, Leuckart, Huxley, Claperede, and others. Indeed, it would seem to be difficult to come to a unanimous opinion, whilst sexuality is allowed by some to have little or no weight in the argument. Brandt remarks as to partheno- genesis, 'fIt is partly to be met with as a normal condition, and partly as an exceptional condition ; as we find to be the case with so many insects. How- ever interesting the fact of the want of a seminal re- ceptacle in the oviparous Aphis may be, from a physio- logical or a morphological point of view, one can nevertheless hardly attribute to it a fundamental signi- ficance, but rather view it as of secondary, adapta- tional import."* This would seem to imply that there is but little real difference between an impregnated and unimpregnated egg (?).

Amongst Insects a modified parthenogenesis has been observed in Sphinx pojpuli, S. ocellata, Arctia caja, and several other genera of Lepidoptera. Mr. Davis raised three parthenogenetic generations from the eggs of the egger moth, Lassiocampa quercus. The marked rareness of the male in Cynips is well known; and the same scarcity may also be noticed in Coccus. Doubtless, however, in some cases males are overlooked on account of their diminutive proportions.

Von Siebold some years ago noted the remarkable fact that reproduction occasionally takes place in the larval phases of some insects. He gave the term Thelytolcy to the process usually known as partheno-

* Dr. A. Brandt, ' Ueber das Ei und seine Bildungsstatte,' p. 55*

116 BKITISH APHIDES.

genesis, and Leuckart proposed the term Arrenotohy to express the power of certain virgin females to produce males.*

2. THE REPRODUCTIVE ORGANS OF THE VIVIPAROUS

APHIS.

The body-cavity of the viviparous Aphis during the summer time is almost exclusively occupied by the embryos and the organs subservient to nourishment. In Aphis proper, in Siphonophora, and the higher genera, the embryos are exceedingly numerous. As many as thirty may be often counted, if the abdomen be snipped with sharp scissors, and the insect be com- pressed under the microscope. These embryos may be seen in all stages of maturity ; those placed nearest the vulva being by far the largest, and showing the eyes, antennas, and limbs fully formed. Their posterior ends are turned towards the vulval opening. Thus the young ones are always born tail foremost.

The first thing which calls attention is the multi- plicity of the ovarian chambers. As in most insects, these coeca unite end to end, and form several long strings, somewhat like threaded beads of different sizes. These strings ; which vary in number in different species, compose two bundles or fasciculi, one of each is disposed laterally. Each fasciculus unites with an oviduct ; and finally the two oviducts coalesce before 11 icy join the vaginal passage.

Thus the ovarian chambers are largest at their attachment to the ovarian duct, and become more and more attenuated as they penetrate deeper into the body-cavity. The terminal chambers are very small ; but each has a delicate filament united to the anterior part, supposed by some to be in communication with the organ which lias the function of a heart.

This end chamber is the seat of important action, for within it the first germinal matter is elaborated.

* Dv. Burnett's transl. Von Siebold's ' Comp. Anat.'

YOLK-COED. 117

Like all the other chambers ; it is formed of mem- branous walls studded with epithelial scales. Within the terminal chamber, several nucleated cells are visible, which are embedded in the periplast. These cells, have, according to Brandt, an amoeboid movable nucleus, and correspond to the ordinary germinal vesicles with their usual spot. After a time a constric- tion forms at the lower end of the terminal chamber, and one of these germ-vesicles passes through, and then it greatly increases in size. This body finally becomes the pseudovum, which is composed of a pseudo- vitellus encompassed by its nucleated cortex ; which Prof. Huxley likens to the blastodermic layers of the true eggs.

The resemblance between the pseudovum and the ovum is completed by the formation of the vitelline membrane which completely envelops the pseudovum. The blastoderm separates into two portions, the outer of which forms a sort of hood over the inner. This hood eventually becomes the abdomen of the larva. Other parts of the blastoderm, in a similar way, separate into the thoracic and cephalic segments.

" The most probable hypothesis as to the nature of the process effecting these changes is that the endo- plast of the pseudovum (germinal spot) divides and subdivides so as to give rise to the endoblasts of the germ. This is more in accordance with what we know of histological development."*

Brandt endorses all the principal views expressed by Prof. Huxley as above sketched, and, indeed, thinks that the resemblance between the early products of the viviparous and oviparous females of Aphis is so marked, that the terms pseudovum, &c, might be dropped altogether, t

A few remarks may here be added as to the signifi- cance of the yolk-cord discovered by Prof. Huxley in Aphis, and by others in Coccus and Psylla. It may

* Huxley, " Reprod. of Aphis," ' Linn. Trans.,' 1858, f Brandt, ' Ueber das Ei ; ' vide note, p. 55, also p. 56.

118 BKITISH APHIDES.

be found also amongst some Coleoptera and Hymen- optera.

Dr. A. Brandt has devoted some thought to the import of this element ; but the function it performs may still be considered yet to want complete elucida- tion. Dr. Brandt states that the basis of the yolk- passage (Dottergange) is sharply bounded by the neighbouring epithelium of the ovary where it appears conical ; whilst towards the apex its outline is termi- nated by the adjoining germinal vesicle of the yolk- forming cells. Its designation of a yolk-cord (employed previously by Huxley and translated Dotterstrang) perhaps best accords with what is really known, than the term yolk-passage, for it has not yet been proved that the vesicles pass through it as a tube. Huxley has not drawn the vesicle as situated within such; and Brandt, in 1878, had not been able there to trace it. This cord occurs both in the parthenogenetic and the fully sexed female organs, though some differences of condition connected with these forms may be pointed out.

This yolk-cord passes from the end chamber of the ovary, through one or more chambers, to any other particular one ; that is, in such cases where the ovaria are many-chambered. This disposition is remarkable ; and Brandt offers the following as a possible explana- tion of its action :

" Let us imagine that, instead of a single ovarian chamber, one or more (connected with the terminal cyst by its yolk-cord) form at the basis of the same. Then those formed earlier will, together with their yolk- cords, be pushed aside by those formed later. After the whole stock of egg-rudiments (Eianlagen), together with their yolk-passages, has been differentiated, then, by the splitting up of the terminal cyst into yolk-forming cells, the change of its remaining undifferentiated elements will take place."

Further on he says, " Every break in the epithelial partition which separates the yolk-forming elements from the egg-rudiments (Eianlagen) can be morpho-

OVIPAROUS FEMALE. 119

logically considered as a yolk-passage. If the yolk- forming elements be immediately upon the yolk, with broad surfaces, and without the separating epithelial layers, then a perfect yolk-passage would seem to be unnecessary, and its production (Zustandekommen) difficult to realise.*

The vagina of the viviparous female is furnished with two muciparous or colleterial glands, the office of which has been before indicated. The spermatheca or sexual pouch is wanting in the organs of the agamic female.

3. REPRODUCTIVE ORGANS OF THE OVIPAROUS FEMALE

APHIS.

The reproductive organs of the oviparous female have anatomically much in common with those of the viviparous ; but the vulva sometimes terminates in a short ovipositor, as may be seen in Drepanosiphum and Phylloxera. This prolongation of the vulva is figured in Pis. CXXI, fig. 1, CXXV, fig. 1.

In Thelaxes dryojohila the vulva, which is always situated between the eighth and ninth abdominal rings, closes by a sphincter ; the action of this is controlled by several bundles of contractile muscles, vide PI. E, fig. 1. The opening thus may appear as a long slit forming the lips of an oval.

The vulva opens into a wide and thick-walled vagina, which is provided with a longitudinal and transversely striated muscular coat. After its continuation forward for a short distance, it is perforated by the duct leading from the colleterial glands, and shortly above this by the opening from the spermatheca.

Beyond this the vagina divides into two wide branches, constituting the oviducts, which spread towards each side of the body. Each of them finally divaricates into five or more tubes, which end in the ovarian chambers or ovisacs.

* Idem, pp. 48, 51, Taf. iv, figs. 103—109, 130.

120 BRITISH APHIDES.

The number of these ovarian chambers varies with the genus and species of Aphis. As a rule, the chambers composing the ovaries of the true female are less numerous than the pseudovarian cysts of the