|
_ |
i |
■ |
|
|
JJI |
• 'j. . |
||
|
■.■■ |
y |
||
|
•*■*•> |
■ |
- |
hH
.
_fe"I
-
■
. s
.
•
I
.
m
1
■PL
• §
« *
in
CO CsJ
r^
10
o o> <fr o
CO
536 B68
A HANDBOOK
OF
BRITISH MOSQUITOES
BY
WILLIAM DICKSON LANG, M.A., Sc.D.
Assistant attached to thr Department of Entomology
LONDON •
PRINTED BY ORDER OF THE TRUSTEES OF THE
BRITISH MUSEUM
AND SOLD BY Longmans, Green & Co., 39, P.1- ;kk Row, E.G. 4 :
B. Quaritch, Lid., ir, Grafton Street, New Bond Street, W. i : Di-lau it Co., Ltd., 34-36, Margaret Street, Cavendish Square, W. i
and AT Till.
British Museum (Natuxai History), Cromwell Road, S.W. 7.
1920
[All rights rtsenxJ.]
PRESENTED
BY
The Trustees
OF
THE BRITISH MUSEUM.
A HANDBOOK
OF
BRITISH MOSQUITOES
BY
WILLIAM DICKSON LANG, M.A., ScD.
A SISTANT ATTACHED TO THE DEPARTMENT OK ENTOMOLOGY
LONDON :
PRINTED BY ORDER OF THE TRUSTEES OF THE
BRITISH MUSEUM
AND SOLD BY Longmans, Green & Co., 39, Paternoster Row, E.C. 4 ; B. Quaritch, Ltd., u, Grafton Street, New Bond Street, \\ . i; Dulai ,\: Co., Ltd., 34-36, Margari r Street, Cavendish Square, W. i
AN 1 1 A I I HI.
British Museum (Natural History), Cromwell Road, S.W. -.
1920 [ . / 7 rights reset 1 1 d. |
%
MAR ^ ly/g
£|fr/ry of TO^t
*V
LONDON I
PRINTED BY WILLIAM CLOWES AND SONS, LIMITED,
DUKE STREET, STAMFORD STREET, S.E. I, AND GREAT WINDMILL STREET, W. I.
fi
PREFAC1
Owing to the important part played by mosquitoes of in the communication of disease, an increased amount of attention h been given to the study of these insects in recent But if the
study of any particular species of insect, no matter from what point of view, be it purely scientific or altogether practical, is to be of real value, it is essential that the species should be exactly identified.
Twenty-one different species of mosquitoes have been found occur in the British Islands ; and it is by no means easy to distinguish every one of these species from all the rest.
It is hoped that this Handbook, prepared with that end in view, will make it possible for the student to identify all the British species without much difficult}-, and not only in their adult flies, but.
far as present knowledge of them will permit, in their larval and pupal stages as well.
The author of the book, Dr. W. D. Lang, has taken great pains in its preparation, and has neglected no source of information that would help to make it <»f value for the pur] for which it
intended.
CllAkl ES J. G \H.\\. A"
British Musi um (Natui u. History), Man ■':, 1920.
C0NTEN1 S.
I. INTRODUCTORY.
A. Gnats, or Mosquitoes, and other fi
B. The Life-historv of Mosqui ro
C. Structural: the nomenclature of pab
i. Imago ......
2. Larva ......
II. IDENTIFICATION.
A. Imago—
i. To distinguish the sexes
2. To identity the genera —
a. Males
b. Females
3. To identify the species —
a. Anopheles
b. Ochlerotatus
c. Culiceila
d. C 11 lex
B. Larva —
1. To identity the genera
2. To identify the species and instar
a. Anopheles
b. Ocldcrotaius
c. Fin I ay a
d. Theobaldia
e. Culiceila f. C it lex
III. SYSTEMATIC ACCOUNT.
|
I. Anopheles — |
||
|
1. |
A. |
maculipennis |
|
2, |
A. |
biftircatus |
|
3- |
A. |
plumbeus |
|
11. Aides |
ciuereus . |
|
|
11. Ochlerotatus— |
||
|
1. |
0. |
caspius ■ |
|
2# |
0. |
curriei . |
|
3- |
0. |
vexans . |
|
4- |
0. |
waterhousei |
|
5- |
0. |
annulipes |
|
6. |
0. |
detritus . |
|
7- |
0. |
nemorosus |
|
8. |
0. |
rusticus |
I
I I
14
$5
44 45
7' "i
1 84
■ ,i
VI
III. SYSTEMATIC ACCOUNT— continued. page
iv. Finlaya genictdata ......... 95
v. Taeniorhynchus richiardii . . .... 98
VI. Theobaldia annulata . . . . . . ... 100
vii. Culicella —
1. C. /nor si /ans .... 102
2. C.fumipennis ...... . . 104
viii. Culex —
1. C./'ifttcns .... ..... 105
2. C. afiicalis . . . . . . .' . . .108
ix. Orthopodomyia albionensis ....... 109
IV. REPUTED, DOUBTFUL, AND FOSSIL BRITISH SPECIES . n 1 V. EVOLUTIONARY AND CONCLUDING REMARKS . . 113
LIST OF PLATES.
The Plates, drawn by E. Ter/.i, are reprinted from K. E. Austen's British Blood-sucking Flics, British Museum (Natural History), 1906.
Plate I. — Anopheles maculipennis Meigen. Female.
The common malaria-conveying mosquito of Europe. Abundant
in Britain.
Plate II. — Anopheles bifurcatus (Linnaeus). Female.
Has been known to convey malaria in Italy. Abundant in Britain.
Plate III. — Anopheles plumbeus Stephens. Female.
Has been artificially infected with malaria, but not known to convey it under natural conditions. Widely distributed id Britain, but restricted during larval life to a sylvan habitat.
Outside the genus Anoplulcs, no mosquito is known to convey malaria.
Plate IV. — Ochlerotatus caspius < Pallas). Female.
Plate V. — Ochlerotatus nemorosus (Meigen). Female.
BRITISH MOSQUITOES.
I. INTRODUCTORY.3
A. GNATS, OR MOSQUITOES, AND OTHER FLIES.
THE object of this handbook is to render as easy -sible the
identification of British Mosquitoes.'- Anti-malarial measures, rendered necessary by the introduction of large numbers of malarious soldiers, have drawn attention to mosquitoes in Britain ; and it is desirable that everyone should be able to distinguish a gnat capable of conveying malaria {Anopheles) from a non-malarial kind Again, diseases other than malaria are known to be gnat-borne, though fortunately not in this country; and it is at least of interest, if not of immediate u that our few British species should be known, in case these should be found to be concerned in conveying an)- di It is in some of
the non-malarial species that difficulties of determination arise, but in most cases, with the help of reasonable magnifying power, the species are easy to distinguish ; and with clear directions and figures there i-^ no reason why everyone should not readily identify most, if not all, the different kinds.
That such help is needed is clear from a consideration of the specimens frequently sent to the Museum in answer to requests for mosquitoes from various localities. Often these are true mosquitoes, but often they are not, or are a mixed bag of mosquitoes and other flies. It is evident, then, that what is first needed is to distinguish a true mosquito, or gnat from flies belonging to other groups.
1 All the text-figures, drawn for this work by Mr. E. ferzi, are very considei magnified. It has not been considered necessary to give the exact magnification in e.ich case. The Plates are reprinted from Major E. E. Austen's British I king Fli
British Museum, 1906.
-The terms "gnat " and " mosquito'' are u>L"i indifferently in this work. A mosquito, and a mosquito is a gnat.
1;
The most telling feature of a mosquito is its proboscis (fig. 6.) Other gnat-like flies may have an elongated face, even ending in a more or less pointed projection ; but a gnat has a proboscis several times longer than the whole head, and easily visible on a near view of the gnat at rest. When once the proboscis is seen, there can be no doubt as to the nature of the insect, if it is gnat-like in general appear- ance. For there are other flies with a long proboscis ; but the general build of these is so different from a gnat's build, that no confusion is possible. To describe, however, a gnat as a gnat-like fly is obviously inadequate. But for lack of any other popular word designating this type of fly, it must do duty while an attempt is made to indicate a gnat's general features. A glance at the figures (e.g., fig. 6 and Plates I.-V.) of more-or-less complete gnats will give a better idea than any description. Delicacy, probably, is the quality that best describes the general build of a gnat. The body is slender and lightly built, and the legs are very long and thin ; the wings also are narrow (figs. I, 6), and the antennae long and thread-like, though densely-plumed in the male (fig. 13).1 Another character, and one diagnostic of a gnat, is the presence of scales thickly clothing the head, legs and the "nervures" or "veins" of the wings (figs. 67, 68) ; and they even form a fringe round the whole margin of the wing (since the wing is limited by a " vein ") ; and in man}- cases cover the abdomen (fig. 16). But these scales are often thin and hair-like ; and, since many flies are clothed with hairs where i-he mosquitoes have scales, this character cannot so easily be used as a criterion without a fairly high magnifying power. In those forms, however, in which the abdomen is densely-scaled (the Culicine gnats), the scales are broad and can be more readily seen. Finally, it must be borne in mind that hairs as well as scales are often present upon the thorax and abdomen of gnats ; also that the scales of gnats are readily rubbed away, so that a bad specimen may appear naked.
A gnat, or mosquito, then, may be known at sight as a fly (that is, a two-winged insect) of delicate and siender build, with a long proboscis capable of use by the female for sucking blood, and having thread-
1 Densely-plumed antennae are very noticeable in the males of some flies nearly allied to gnats, and must not be considered as peculiar to, but only as a characteristic feature of all gnats.
like antennae with whorls of sparsely-distributed hairs in the female (fig. 14) and of dense hairs in the male (fig. 1 j), giving the antenna of a male gnat a plumose appearance. Further, viewed under a moderately
strong magnifying power, the head, legs, veins of the wings, and often the abdomen, are seen to be densely clothed with scales. If a gnat caught, so that the venation of the wings can be examined, it may be known by arrangement of the veins. This is shown in tig. 1, and the most characteristic feature is the presence towards the tip of two parallel forked veins (longitudinal veins 2 and 4) with an unforked vein (longitudinal vein 3) lying between them and also parallel with them. The stalks of the two forked veins are continued back- wards, the lower one to the base of the wing, the upper to a point on longitudinal vein 1 where it branches from that vein. The middle,
costal vein supernumerary cross vein
subcostal vein
6th long.vei
posterior cross vein 5th long, vein
anterior or mid cross vein
. 1. — Wing of Mosquito : Citlex pifiens (Linna
11: long. vein
2n:1long. vein
3rd long, vein
ong.vein
4th
unforked vein abuts against cross-veins joining the stalks of the two forked veins.
Thus, even if a specimen is so rubbed that the scales are removed, a gnat may be known at once from other flies (except Mochlonyx and Cluiobonts — allied genera which have no long proboscis) by the wing- venation. And this, as well as the presence of a proboscis, is a useful test when a gnat is compared with other flies that are frequently mistaken for true mosquitoes or gnats. Three of these will be mentioned. First, there are numerous species ^\ Chirotwmtis and allied flies that are often noticeable for occurring in immense numb in the neighbourhood of water, and have a very gnat-like appearance, especially the males with their densely-whorled antennae. The flies have no proboscis and are not covered with scale The
B 2
wing-venation is shown in fig. 2, and is seen to be simpler than that of a gnat. The larvae of some of the commonest species of Chiro- nomus live in water-butts in company with larvae of Culexpipiens — the Common Gnat ; but their appearance is very different from the gnat larvae, and some are bright-red and popularly known as Blood-worms. The}- make a more-or-less coherent case of slime and dirt, and live in it on the bottom ; while Cu /ex-\a.rva.e swim freely at all depths and
Fig. 2" — Wing of Chironomus plumosus (Linnaeus).
frequently rest at the surface. The Chironomus-fiy is interesting for its habit of raising a pair of legs and waving them in the air like feelers when it is resting and when danger threatens. Mosquitoes have the same habit, but while Chironomus raises its fore-legs, mosquitoes raise their hind-legs. Doubtless correlated with this habit is the great length of the fore-legs in CJiironomus and of the hind-legs in mosquitoes.
Fir.. 3. — Wing of Trichocera regelationis (Linnaeus).
Other flies constantly mistaken for true gnats are certain gnat-like kinds of the family Limnobidae, for instance, species of the genus Trichocera. These are familiar for dancing in small swarms in sheltered situations throughout the winter, and are, consequentlv, sometimes known as Winter-gnats. The build of a mosquito was described as delicate ; that of a Trichocera mav be called flimsv, so fragile are these flies even compared with gnats. There is, of course, no long proboscis ; and the bodies are bare or but slightly hairy.
The wings arc broader than mosquitoes' wings, and the venation is far more complex (fig. 3). The larva- are not aquatic.
Rhyphus fenestrate is a very common fly frequently mistaken for a mosquito. It is found in houses, outhouses, etc., often in company with Anopheles maculipennis. Having spotted wings (fig. 4), at sight it superficially resembles that species. The wings, however, are wider, and the spots consist of the pigmented wing-membrane ; whereas, in Anopheles maculipennis ; they are formed by scales ma more thickly there than elsewhere along the veins. Besides, Rhyphus has no scales, no long proboscis, and its build is more thick-set than that of a mosquito.
. 4.— Wing of Rhyphus fmtstralis Scopoli.
B. THE LIFE-HISTORY OF MOSQUITOES
The eggs of British mosquitoes are laid during the warmer parts of the year generally on water, either singly (by the genera Anophel A'c'dcs, Ochlerotatus and Finlaya), or glued together in floating masses called rafts (by Taeniorhynchus, Theobaldia, Culicella and Culex). As
far as they are known, the eggs of all species float, and .ire several times longer than wide. In most species the}' remain from one to several days before hatching, and the length of time is pro! .abb- more determined by the temperature than by any Other cause The emergent larva (figs. 10 and 11 show a full-grown larva) is an elongate, limbless grub with a wide thorax and head, and wit variously-shaped and often tufted hairs symmetrically arranged along its whole length. Some of the most remarkable of these hairs .ire a pair of very dense tufts called brushes (figs. 10. 11 and [2), lyii the underside of the head in front of the mouth, and resembling v moustache. These the larva continually moves backwards and forwards, and thereby entangles in them the particle nic
matter on which it feeds. These particles arc then combed out of the brushes by some hairs which grow on the mandibles, and passed into the mouth. Other particles are swept by the current created by the brushes on to the other mouth-parts and entangled in them.1 Thus the larva feeds and grows, and in a few days undergoes ecdysis, that is, its skin splits, and a second larval form, or instar, emerges, resembling the first in general features, but differing in detail. In all the British species of which the first larval instar has been examined, the group of hairs (fig. II, FIN) lying medianly and ventrally on the last abdominal segment, and forming the fin-like organ characteristic of mosquito larvae, is absent, but is assumed at the first ecdysis or moult by the second larval instar. There is also a minute tooth or egg- breaker'1 on the surface of the head of the first instar, having a vertical motion produced by muscles attached to its base, and used for forcing an exit from the egg. The third and fourth larval instar closely resemble the second, but are progressively larger and are of longer duration. Indeed, some forms {e.g., Anopheles bifurcatus) spend the whole winter in the third or fourth larval form, but otherwise the stages are generally run through within a few weeks. The larva moves in wriggling jerks, and an Anophe/es-\a.rva can dart backwards with great nimbleness. The larva frequently rests just beneath the surface, and there can breathe by means of a pair of stigmata placed one on each side of the mid-line of the penultimate segment (the eighth abdominal), and placed in the Culicine gnats at the end of a long tube — the siphon. While thus floating, the larva explores the lower side of the surface-film and its neighbourhood for food, often bending its body sideways to reach a favourable spot. Owing, presumably, to the action of the brushes, it is kept gently moving forward while feeding, whether it is floating on the surface or browsing on the bottom as it sometimes does, especially in certain species ; and when a Culicine larva on the surface curves round as just described, it takes on a rotary motion, circling round the axis of its siphon. Should the stigmata tend to become clogged, or breathing be otherwise obstructed, the larva bends round and passes the siphon through the brushes,
1 Set '■. II. V. Nuttall and A. E. Shipley, 1901, Journal of Hygiene, vol. i., p. 57.
2 See Y . YV. Edwards, 1919, Annals and Magazine of Nat. Hist., Series 9, vol. iii., pp. 372-6. It is shown below in figs. 98-99a (p. 55), in the mid-line of the head and just
1 ior to the centre.
apparently to clear away the obstruction, just as a cat uses its te to clear its fur. This action is one of the first signs of distn exhibited by the larva in an unfavourable environment, even when it brings no relief, as when the surface of the water is i | with
paraffin. Four finger-like, delicate processes, the analgills (figs. [O, i i >, project from the end of the last (ninth) abdominal segment, and probably allow the larva to remain longer beneath the surface than
FlG. 5. — Pupa of nereus.
would be the case if it were dependent for breath upon its stigmata alone. This accessory breathing-apparatus would also explain how a hibernating form can remain alive in the mud while the water above is frozen at the surface.1 Again, the larva of Taeniorhynchu
1 It has been shown that certain mosquito larvae can remai aerated water for a considerable time after I f the anal gi
ably, through the general integument. See J. VV. S( ' M , i ". Bull. ! vol. vii., pp. 277
continually on the bottom, and has a siphon modified for piercing submerged plants and obtaining from them the air it needs.
The instar succeeding the fourth larval instar is a pupa. It does not eat, and, except when disturbed, floats just beneath the surface of the water. Like the larva, it can swim by wriggling jerks, but is far more nimble and restless when alarmed. It is also more buoyant than the larva, and this buoyancy becomes progressively greater as the time for emergence approaches. The pupa has a very different aspect from the larva (fig. 5). Generally speaking, it resembles a comma with a gigantic dot. The dot of the comma is the head and thorax of the pupa, and the tail its abdomen. The abdomen ends in a pair of lobe-like fins ox paddles. The outline of the sheath covering the rudimentary wings can be seen on the sides o( the thorax as in the chrysalis of butterflies, and the sheathes protecting the future legs, mouth parts and antennae of the fly are prominent on the surface of the pupa. As in the larva, there is a single pair of large stigmata or breathing pores, but in the pupa they are placed on the thorax, and prolonged into expanding funnels standing out from the thorax like ears.
The pupal instar is of short duration, generally lasting but a few days. Before emergence the pupa begins to acquire a silvery look, due to air that is forced between the pupal integument and the enclosed imago. This air causes a greater buoyancy of the pupa, which is increased as more air is forced in, and the pupa appears more silvery. It is then with difficulty kept from the surface and sometimes fails to retain its equilibrium, temporarily rolling over to one side or the other. It rides so high in the water that finally the dorsal surface of the thorax projects and remains dry. This dry patch then splits along the mid-line, and very quickly the thorax of the imago is pushed out. The gnat thus emerges in a humped attitude, with its head sunk on its breast, the antennae, palps, proboscis, and legs still held in their pupal sheathes, and the abdomen but little outpushed from the pupal skin. The imago still continues to move vertically upwards, with the dorsal surface of the thorax foremost, the antennae and proboscis closely appressed to the thorax, and the legs, with their tips still in their pupal sheathes, lying along the emergent abdomen, the tip of which is also still encased. In this condition the floating insect appears most
unstable, with the thoracic mass high above the cenl gravity of
the system. But, in fact, its equilibrium is by no means easily disturbed, as may be proved by gently blowing upon it, when it spins round most readily, like a weather-cock, but does not capsize. Indeed, an upset in this stage would be fatal, as, once wet, the ins could not resume its vertical position, and would drown. The pupal skin, split open and completely emptied of the air that forced out the imago within, no longer rolls to this side and that, but li< the surface without rocking. Gradually the emergent fly draws its limbs free, the wings harden, and it flies away.
The habits of various species differ, but generally British mosquib hide away during the day and in chilly weather, and fly forth in the evening if the weather is warm enough. It is mostly then that the females bite and the maies swarm. The males do not suck blood, but some have been observed feeding upon flowers. It is the habit of the males to dance in swarms in the evening at definite sheltered spots, sometimes in company with the males of other species of gnat or of gnat-like flies. The females wander about sing!}-, and when one approaches the neighbourhood of swarming males, the swarm becomes very agitated and the dance a frenzy. The stimulus exercised by the frenzied swarm breaks down any inhibitions controlling the female, who, throwing away reserve, darts into the swarm, is seized by a partner, and the couple fall out of the dance. The swarm then resumes its normal motion and awaits the arrival of another female. It thus appears that the swarming of the males is no aimless behaviour, but has a bionomic significance, producing the requisite stimulus that, reacting on the female, leads to her attraction and capture, thus unlocking a whole chain of consecutive stimuli which produce an orderly sequence of reproductive proces
But the stimulus of the male swarm may not in all the
only unlocking action. There is some evidence to show that in certain species of Anopheles, the female requires a meal of blood before she is ready for pairing' ; and, after pairing, a second meal before oviposition.
1 H. E. Anncti, E. E. Austen and R. K«>~>, 1002. k ' aria 1 \
being .Memoir II. of the I-;- ol of Tropical Medicine, p. 21. I
the absence of conditions suil tble for swarming and not the a cause of the females' failure to oviposit. Th nothing in I
experiments to negative this possibility.
Imi sindhi cai'SPSs, tinem)„ aim mmnffed femmale will be imidinleiremitt to a swaimm off
--. i - - _ amid time cSaain of reprodnactivie
- - amly t ■ omitrerpojsitiiom) of amrc»tlmeir ©mgamilsmin
:i>e miecessairy sttinmnnliins. TTmis iimfaodmKctiioim of a
.-(tor inn trine life-cycle eviden:
-..3ne comilrirmiiiiiatriioim of ttftnc - - jmmplicator
.md wc . It Imave Saeer
mmeasmnre to mmee - . mneinge: : ~ If it <c©nnld foe slno^ 1
■:m mm trlnose trlnatt coponlalte icadily, Mood-simckiiE g ~Jne
repircadluBdL - ."aere a laimitt footln as to b
tBne olood-snodldiimg Una": : : toeem casual amid mrnoire e i
gemeo - evesm mie: . - ' n s It - :'.r :.2jmse off estinTKdtiomu For it seemms clear trlaat tfc e
:vofced to snack platmtt-jimices. Bottfln sexes of : - jaTe foeemi ©toseirwd sancMrr ffloweas^ amid tine femmi i'areigmi species seldomm or nue^er smtelk Mood. Iff mmdnVndci:- £„ pHaimfr-^amrTlriiinrj nmKDsqniitoES appealed w. ~jl -z ; BnaSjottofc' - arMmig rniarniFi-Wooded aTmiwrmgls, aimd -
stiinmmillattmnig lepirodmicttiionn mm tBne ffemmale, it is ewEetmt ((smmce sanelm mnals wobdM mm©ie leadnlly irepnToxdronce)) ttlnat tikis InaMt, iff Ine: 3smmittfied at ami acceleiiattiffi^' irate mumtil tine wllnc - trlniirstty for Wood! — as mmamry i is a ffact ttfinatt dniSeiremitt degrees off strimnnmllmts aire mieetc e - dinleiremitt species off sjimalL. Gennenalliy we mma tnre
res - _ :Jn degme; • - -•...- stmdm a :- ~
"ffsBflfliHy ~ somme neqaimre trine swatrmmmmg off the nroalle- . • -
--amine, like trine Jbmig • 1 mmemitrioimed,
- ime a mnwaall ©ff Mood as well as trine swar" I" l gienBeiral! wiew off Sine amnkmal kmntgdomm,, trMs samme di-- 1 i mmTTriTrnffy iresgtmr i : 'isen^Tafole. Tlie sntanatfikaiii mi
~. a s — Inn ceirtraimi : a camise mnmkic : ahe
jcttuwe " -":'-.-:" loot Ine:
rue weire ami imicireasiinng' imiMM: -; annate win : i^'opeicommeomiL
. ae mmaDe. If tflnrls Mttcfln ire : .-
. - inn tt .
1 1
as a block caused by factors inhibiting the read: f the f
increases as the race evolves, and generation succe
there will come a point at which no i onding t on th
of the male will overcome the female's reluctance, and the i will
perish. Such a process may be in action among m
The swarming of the males at first removes inhibiting fad tut
later the meal of blood is needed as well ; should the inhibiti
continue to accumulate, a new device must be found, or the race will
become extinct.1
Some British mosquitoes hibernate as impregnated fee and issuing forth in spring, lay eggs, and thus start a new c ■ ith
the new season. Others hibernate as larvae (or, in some eggs), and the imagines of these species die • ff at the end of autumn. In some species there appear to be but one or two broods in the year ; while in others, brood succeeds brood throughout the summer ; but the rate at which the life-stages are run through, and consequently the number of broods produced in a season is probably primarily determined by the temperature. Hot weather sometimes . . in Ochlerotatits netnorosus) has the effect of checking the life-h by
drying up the breeding-places ; but as a rule the warmer the weather. the faster the progress o\ the life-cycle.
C. STRUCTURAL: THE NOMENCLATURE OF PARTS
i. THE IMAGO 1
It is impossible to identify mosquitoes without a nomenclature of their parts. But it is not intended to discuss their morph much
further than is necessary for purposes of identification.
Figure 6 shows the parts of an imaj fly. The the
antennae, the eyes and the mouth-parts. Most of the last i ite
the proboscis ; but the maxillary palpi (generally referred to simply as the palps) are a pair of jointed, I tructures, lyii
one on each side of the proboscis, usually very short in the f but long in the male and with tufts >'t" V w^ hairs in
1 Of course it may be argued that the stimulate the male, such stimulation precedes in the male. Such a contention would not inval merely shift the point of its application.
[2
figs. 18-21). The rest of the mouth-parts compose the proboscis.. The mandibles and maxillae are pairs of long, flattened, thread-like organs lying within the proboscis sheath and concerned with piercing the skin during biting. The proboscis sheath is formed by the labium, and has the form of a very much curved gutter or a tube not quite complete above, and does not enter the skin when the mosquito bites, but abuts against it, bending ventrally as the piercing mouth-parts are thrust deeper into the host. Almost at its tip it bears a pair of little lobed pieces — the labclla (fig. 6) which project beyond the tip and serve to guide the piercing parts. The channel of the labium is closed above by a similar, but far more slender gutter open ventrally, called the epiphafynx — an extension of the labntm. This terse description by no means exhausts the structure of the proboscis, nor explains the complex mechanism whereby the gnat simultaneously sucks blood from its host and injects into him saliva and whatever the saliva contains. Such description is beyond the scope of this work.
The thorax (fig. 6) bears the wings, the halters (vestigial hind- wings) and the legs, and is constricted posteriorly by a groove which cuts off a narrow, posterior strip — the scutellum. Projecting from the posterior end of the thorax, beneath the scutellum, and overhanging the first abdominal segment is a dome-shaped prominence — the meta- notum, or, better, the postscutellum.
The details of the wing-venation are shown in. fig. 1. The vein forming the margin of the wing is called the costal vein ; that immediately succeeding it, and meeting the costai vein about half- way between the base and tip of the wing, is called the sub-costal vein. Succeeding this, and running from the base nearly to the apex of the wing, is the first longitudinal vein. The second longitudinal vein branches from the posterior side of the first longitudinal vein, and forks into an anterior and a posterior branch near the tip of the wing. The third longitudinal vein rises from the second longitudinal vein, and runs unbranched to the margin of the wing between the posterior branch of the second and the anterior branch of the fourth longitudinal vein. That short part of it, from where it branches from the second vein to where it turns towards the margin, is called the supernumerary cross-vein. The anterior, or mid cross-vein, joins the end of the supernumerary cross-vein to the fourth longitudinal vein,
■3
which rises near the base of the wing, and is divided into an ant and posterior branch shortly before it reaches the margin. The fifth longitudinal vein also rises from near the base of the wing, and
ANTENNA
HEAD
EYE
THORAX
SCUTELLUM METANOTUM
HALTER
ABDOMEN
HIND LEG
Fir.. 6.— Generalised diagram of n show the nomenclature of •
14
divides about half-way along its course into a curving anterior branch and a straighter posterior branch. A stout vein, the posterior cross-vein, joins the anterior branch of the fifth to the fourth longitudinal vein.
The legs (fig. 6) are divided into the following joints, namely from base to apex, the coxa, trochanter (a very short " corner " joint) femur, tibia, tarsal joint I, tarsal joint 2, tarsal joint 3, tarsal joint 4, tarsal joint 5. Tarsal joint 1 is often, in fact generally, spoken of as the metatarsus ; but I abandon this term as incongruous. The last tarsal joint ends in a pair of ungues or claws, which may or may not be toothed. The junction of the femur and tibia is the knee.
The abdomen consists of ten segments, but only the first eight are readily seen. The last two are modified for reproduction, and are more or less telescoped into the eighth segment. Generally, all that can be seen of them are the cerci of the ovipositors (fig. 6), borne on the tenth segment of the female, and consisting of a pair of short leaf-like projections ; and, in the male, the great forceps, with their proximal joints or side-pieces, and their distal joints or claspers (see fig. 59), terminating in a claw . Smaller accessory organs, harpes and Jiarpagones, occasionally are present, lying between the large forceps (see fig. 59).
2. THE LARVA (FiGS. 7-12).
The head of the larva bears several pairs of hairs, sometimes so arranged as to form transverse rows. On the upper surface of the head these hairs mostly occur on what is generally called the clypens, a chitinous plate occupying the whole width of the head anteriorly, but narrowed posteriorly by two converging sutures, which separate the clypeus from lateral plates of chitin carrying the eyes, and in front of the eyes the antennae. These clypeal hairs are of great importance in Anopheles, and it is as well that their nomenclature should be straightened out. Typically, the clypeal hairs fall into four rows. The most anterior row is on the anterior edge of the clypeus, and consists of two pairs of hairs. These two pairs may be called the inner anterior pair and the outer anterior pair (fig. 7, i.a. and o.a.). They are present in Anopheles (fig. 7), and have been generally described simply as " clypeal hairs"; but they are absent in all other British genera. (A pair of short hairs occurs in front of the clypeal edge in both Anophelines and Culicines, and may be termed the
<5
pre-clypeal pair (figs. 7, 8, 9. //■.<-.). The second row consists of a single pair of pre-antennal hairs (figs. 7, 8, g,pr.a.), lying, in AnopJu (fig- 7). Just anterior to the level of the antennae, but rather in- differently placed in the Culicines (figs. 8, 9) with regard to this le\ In Culicines, too, the)r are often extremely small and inconspicuous. The third row consists of three pairs of hairs, the inner, mid, and outer post-antennal pairs (figs. 7, 8, 9, i.pb.a., mpo.a., o.po.a.), lying just posterior to the level of the antennae. The row tends to have a
m.po. a
Fig. 7. — Distribution of hairs on head of Ano- pheles larva.
Fig. 8. — Distribution of hairs on head of Tluo- baldia larva.
FlG. 9. — Distribution of hairs on hi li>\ rva.
posteriorly-directed curve. In Ochlerotatus (fig. 9), owing, apparel to the forward and inward displacement of the mid post-antennal pair, the second and third rows are confused in arrangement, and the inner post-antennal pair lies nearly directly behind the mid post-antennal pair. In the first instar of Ochlerotatus at least, in the sp< nemorosus, and in Finlaya geniculate the mid post-antennal pair is in a line with the others. The mid post-antennal pair has a somewhat intermediate position in Taeniorhynchus, while in Ae'des, Tfuobaldia (fig. S), Culicella and Culex, their position i- normal. The fourth 1
1 6
STIGMA
Fig. io. — Larva of an Anopheline gnat {i.e., of the genus Anopheles). Dorsal, view. The ninth abdominal segment is twisted round so as to present a lateral view, to show
the fin.
ANTENNA
EYES
TERZt i
IX™ ABDOMINAL SEGMENT
BRUSH
HEAD
ABDOMEN
SIPHON
ANAL GILLS
TUFTED HAIR
STIGMA
FlG. ii. — Larva of a Culicine gnat (/.*., one of a genus ol
species figured is A nereus). Dorsal view. The eighth and ninth ab i
segments are twist ! so as to present a lateral view to show I
comb and fin.
i8
consists of a single pair, the vertical hairs (figs. 7, 8, 9, v), which are always very small. In a row with them and just across the suture is another pair of very small hairs, which may be called the trans-sutural pair (figs. 7, 8, 9, tr.s.) ; while a third small hair, the ocular hair (figs. 7, 8, 9. 0), lies in the neighbourhood of the eye. The hairs on the lower surface of the head have not been used to distinguish the species, and consequently are not described in detail.
On the head (figs. 10, II, 12), laterally, is a pair of antennae, and
Maxilla
Triangular plate
Labial sclerite
Fig. 12. — Ventral view of head of Anopheles.
posteriorly to these a pair of eyes. Each eye is divided by a constric- tion into a larger anterior portion and a smaller posterior portion, which may be completely detached. Ventrally and anteriorly (fig. 12) the head bears a pair of brushes on lateral lobes of the labrum called flabellae; a median lobe-like pala turn also bears a tuft of hairs (omitted to save obscurity in fig. 12). In the middle of the ventral surface of the head are mouth-parts, of which'the most prominent are the heavily-chitinised teeth of the mandibles, and the labial sclerite of the labium, against which the mandibles appear to bite. The maxillae
19
are more or less flat, inconspicuous organs with fringed edges. It is
difficult to see that the maxilliary palp is connected with its maxilla ; on the contrary, it appears at first sight to be an independent organ. It is often minute in Culicine larvae, bill larger and somewhat prominent in Anophelines. The labium is a complex structure, con- sisting of four members placed one upon the other in dorsal-ventral sequence, like the leaves of a book. Ventral-most and outermost is a plain, wide, tongue-shaped chitinous flap, the labial flap. Next a this is a more or less triangular plate, feebly chitinised, with toothed free edges and often fringed with long hairs. Dorsal to this triangular plate is the heavily-chitinised labial sclcriU\ also triangular, and in shape very closely resembling a shark's tooth. Lying dorsal to the labial sclerite is the labium proper, a peculiar structure more or less shaped like a hollow cube, with the posterior and lateral faces repre- sented only by a framework and the ventral face narrowed to a bar. On the dorsal and anterior faces are numerous chitinous teeth.
The thorax and abdomen (figs. 10 and 1 1) of the larva are character- ised by numerous hairs of various shapes- simple, branched or tufted. The eighth abdominal segment bears a pair of stigmata dorsally, and laterally an arrangement of flattened hairs or scales called a comb. Each scale is posteriorly directed, fringed with minute cilia-like hairs, and often terminates in a stout spine or bristle. Primarily, the comb appears to consist of a dorsal-ventral row of flattened hairs or scales lying parallel with one another. In the Anophelines the scales retain their primitive parallel condition, but are united at their bases by a broad band of chitin so as to form a comb-like structure (fig \;.
89-91, 95-97). Moreover, the band is continued dorsal-wards, and. passing posteriorly to the stigmata, is continuous with its fellow on the other side. A second comb-like structure, lying somewhat anteriorly and ventrallv to the comb, is present in the first instar in Anopk (figs. 100, 101, ioitf). In most adult Culicines the primitive single row of parallel comb-teeth becomes broken up into a more or less confused group, though the teeth tend to remain parallel and directed posteriorly. Finlaya geniculata, however, and the first instar of those Culicines in which this stage is known, retain the primitive single-row arrangem- of their comb-teeth.
In the Culicines the stigmata opening on the eighth segment
2
20
carried up to the end of a long median projection called the siphon (fig. u). This is heavily chitinised on the distal half only in the first instar, but throughout its length in succeeding instar. It carries one or more pairs of tufted hairs (simple in the first instar) ; and on each side, on its proximal half, a row of flattened toothed scales somewhat resembling those of the comb. Each of these rows is called a pecten, each scale composing it is a pecten-tooth, and each projection on a pecten-tooth is a denticle. The anus is situated at the end of the ninth abdominal segment, and is surrounded by four thin-walled papilliform processes, the anal gills. Ventrally, the ninth segment carries a series of tufted hairs arranged in an antero-posterior row approximately in a median plane, but actually alternately a little to left and right of the mid-line. They are inserted on chitinous trans- verse bars, which viewed from the ventral side of the larva have a gridiron-like aspect. Collectively, these median hair-tufts form a rudder-like fin, which probably steadies the floating larva by pre- venting a rocking motion, and adds power to a sweep of the tail for purposes of motion. In those forms in which the first instar has been observed this fin is absent, and its place is taken by simple posteriorly- directed appressed bristles.
II. IDENTIFICATION. A. IMAGO.
i. TO DISTINGUISH THE SEXES.
In identifying British gnats it is necessary first to distinguish the sexes. When a specimen is secured, the question whether it is a male or a female must be determined before the following keys can be used.1 Luckily, to determine the sex is a simple matter, for there are two easily-seen characters which afford infallible tests, namely, the structure of the antennae and the shape and appearance of the distal end of the abdomen.
1 The keys for identification here used are founded upon those given by F. W. Edwards, 1^12, The Entomologist, vol. xlv., pp. 191, 217, 260 ; moreover, further information given in these and other papers by the same author has been freely used, and much help has been rendered me by Mr. Edwards in correspondence and conversation, for which I take this opportunity of tendering him my best thanks.
2 I
In both sexes there are whorls of hairs on the greater part of the antennae, a whorl at each joint, except distally. But, while in the female the hairs forming these whorls are scanty, so that to the unaided eye the antennae are inconspicuous; in the male these whorls are so dense, and the hairs composing them so long, that the antenna as a whole appears as a thick plume, and the pair of antennae form, with the palps, the most conspicuous feature of the head. Figs. 13 and 14 show, respectively, the antennae of a male and a female gnat.
T1£I=I.Zt ,
Fig. n. — Antenna of male Aides ciiu
Fie. 14.— Antenna of femal-
The abdomen of the male gnat (fig. 15) is, on the whole, club- shaped. It is somewhat narrower anteriorly, swell- rather quickly towards the posterior end, begins to taper rapidly, and then is truncated. It terminates in a pair of rod-like bodies bearing many long and stiff hairs, and generally lying side by side, but sometimes somewhat diverging. These are the side-pi< f the forceps
22
largest pair of clasping organs, and each bears distally and jointed with it a long thin bristle-like clasper, hardly visible to the naked eye, and generally bent at least at a right angle to the stout side- piece.
The abdomen of the female (fig. 16) is widest near the middle, tapers very slightly anteriorly, more decidedly in a posterior direction to more or less of a point, and ends in a pair of small leaf-like cerci, sometimes called ovipositors. Ventrally there is a median, lobed
Fig. 15. — Abdomen of i Anopheles maadipennis.
Fig. 16.— Abdomen of 9 Culex pipiens.
unpaired piece. The ovipositors cannot be mistaken for the forceps of the male, being of a far smaller size as well as of a very different shape.
It should also be noted that in every British form, except Aedes cinereus, the palps of the male are longer than the proboscis ; and in every British genus, except Atwpheles, those of the female are much shorter than the proboscis.
2. TO IDENTIFY THE GENERA.'
a. Males.
When the sex of a specimen has been determined, it is possible to discover its genus by means of the following instructions. If the specimen is a male, the palps afford the greatest help for this determination. At'des is at once known by its palps which resemble those of female Culicines, being less than one-sixth the length of the proboscis (fig. if). Aides may also be known by the wide distribution of broad, flat scales on the head (fig. 29). In most gnats the flat-lying (as opposed to the up-standing) scales on the head are nearly all narrow, the few broad ones being confined to the lower and posterior
Fl<;. 17. — Head of male Aides cinerais, from the side, to show the short palp.
parts of the sides of the head. In Aides, the broad scales invade the crown, and the narrow scales on the top of the head are confined to a median crest. This is so in both sexes.
In all British gnats other than Aedes, the palps in the male> are longer than proboscis, and, lying on each side of that organ, appear as feeler-like structures, thickly scaled, and with certain areas of their distal parts densely clothed with long, fine hairs. They are five- jointed, though the scaling and tufts of hair often obscure the boundaries of the joints. In Anopheles (fig. 18), the last two joints are short and thick, and together form a hairy head to the long slender stalk formed by the proximal joints. The whole palp some- what resembles a golf-club. Anopheles is also distinguished from all
1 The diagnostic characters do not necessarily hold outside the British species.
24
other British gnats by the abdomen (see fig. 15) which, except for numerous outstanding hairs, is naked, and has none of the scales which densely clothe the Culicine abdomen in both sexes (see fig. 16). The scutcllum, too (see figs. 42, 43), is narrow, and not markedly trilobed as in Culicine genera (fig. 22).
1
y
m
Ilk '.I r'i
18
20
■wz
TEFIZI—I
21
Fig. 20. — Palp of male Och- krotatus caspius. (Xote : the palp of male Tae- ?i iorhynch us rich ia > < Hi is of this type.)
Fig. 18. — Palp of male A ncpheles maculipennis
(from above). Fig. 19. — Palp of male Calex pipiens (side view).
Fig. 21. —Palp of male T/ieo- baldia annulata. (Note : the palp of male Culi- cella is of this type.)
The male Culex has very distinctive and easily-distinguished palps (fig. 19). The terminal two joints, though hairy, are thin, taper distally, and are curved upwards through an angle of nearly 90°.
The remaining genera have palps very much alike. The last two joints are long compared with those of Anopheles, and do not turn
upwards through an angle of 90 like those of Culex. In Ortlio; myia the last joint is about as thick as, but only about a third as long as the last but one. In Tlieobaldia (fig. 2i), and Culicella the
Fig. 22. — Scutellum of a Culicine gnat.
joint is somewhat thicker than the last bu"t one, while in 0 elder otatus (except in 0. rnsticus), Finlaya and Taeniorhynchus it is slightly thinner (fig. 20). The hairs, however, render this difference somewhat
FlG, 23. — Male genitalia of Cuh
obscure, and the genitalia are a more convincing guide. If the end of the abdomen is cut off, boiled for about five minutes in a fairly sti solution of caustic potash, placed on a microscope-slide, and th - pieces separated with needles, even a fairly low-power lens will n
26
the remarkable difference in type between the genitalia of Theobaldia, Culicella and Orthopodomyia on the one hand (fig. 23), and Ochlerotatus, Finlaya and Taeniorhynchus on the other hand (figs. 59-66). Theo- baldia annulata (the only British species of Theobaldia) may at once be known from Culicella and OrtJiopodomyia by having spotted wings ; Orthopodomyia albionensis (fig. 130) is a black form with thin, white
Fig. 24. — Femur, tibia and tarsus of hind-leg of male Taeniorhynchus richiardii.
lines on the thorax ; and Taeniorhynchus richiardii can be dis- tinguished from Ochlerotatus by the first hind-tarsal joint which has a median pale band (fig. 24). In Ochlerotatus, too, both the claws of the fore- and mid-feet are toothed in both sexes ; while in Taenio- rhynchus the smaller claw on these feet is simple (figs. 25 and 26).
Fig. 25. — Claws on fore-foot of male Ochlerotatus caspius.
Fig. 26. — Claws on fore-foot of male Taeniorhynchus richiardii.
Finlaya geniculata, the only British species of the genus, differs from the British species of Ochlerotatus in the pattern of the abdominal segments. The light portions of the abdomen consist of a lateral pair of brilliant white triangular spots on each abdominal segment (fig- 58) ; while each segment in Ochlerotatus has a more or less complete pale band (figs. 51-57).
- /
The following key summarises the generic differences detailed above : —
Mai es.1
A. Abdomen without scales (fig. 15). Last two joints of the palps
short, and together form the head of a club-shaped palp (fig. 18). Scutellum narrow and not markedly trilobed (rigs. 42, 43) I. Anopheles.
B. Abdomen densely clothed with flat imbricating scales [fig. I
Scutellum wider and distinctly trilobed (fig. 22 . / 1. Palps not one-sixth the length of the proboscis (fig. i-
Flat-lying scales on the crown of the head nearly all wide «
(fig. 29) II.
II. Palps about as long as the proboscis. Flat-lying scales on the crown of the head all narrow (fig. 28) ; wide scales confined to a few at the sides of the head posteriorly.
a. Last two joints of the palps tapering and upturned through an angle of nearly 90 degrees (fig. 19) . . . .VIII. Culex.
b. Last two joints of the palps not upturned. 1. Terminal joint of the palp slightly thicker than the
last but one (fig. 21). Genitalia of male of the type
shown in fig. 23.
' a. Wings spotted. Posterior cross-vein nearly in a line
with mid cross-vein (fig. 33). Second abdominal
segment with a pale median stripe (fig. 36) .
< (3. Wings plain. Posterior cross-vein, though near mid
cross-vein, yet not nearly in a line with it (fig. 34 .
Second abdominal segment without a pale median
stripe (fig. 37)
Terminal joint of the palp slightly thinner than the last but one (fig. 20), except in Ochlerotatus rusticus. ( Genitalia of male of the type shown in figs. 59-66.
a. Smaller claw on fore- and mid-feet simple (1
Firsthind-tarsal joint withmedian pale riny ii^.24 V*. Taeniorhynchus. /3. Both claws on fore- and mid-feet toothed tig. 25 First hind-tarsal joint without median pale ring. 1 i. .More or less complete, pale, abdominal band- :
palps slightly longer than proboscis ii. Brilliant, white, triangular lateral abdominal spots (fig. 58) ; palps slightly shorter than proboscis .....-• Terminal joint of the palp about as thick as, and only a third as long as the last but one. Genitalia of the
type shown in fig. 23 IX. Ortkop
(O. albioncnsis a black species with thin white lines on thorax.)
VI. Theoba
VII. Culicella.
V
III. Ochlerotatus.
1 V. / in
1 See also characters of Stegon a p. 112.
28
/;. Females.
To determine the genus of a female mosquito, the palps are not conspicuously useful, except in Anopheles and OrtJiopodomyia. The female Anopheles has bristle-like palps about as long as the proboscis (fig. 27), in OrtJiopodomyia (fig. 130) they are little more than a third as long, while in all the other female British Culicines the palps are not one-fourth as long as that organ (figs. 28, 29).
The females oiA'e'des, Ochlerota tns, and Finlayahave long-tapering abdomens, and the first two have long cerci (figs. 51-58) ; while in the
Fig. 28. — Head of female
Ochlerotatus c as phis.
Fig. 27. — Head of female Anopheles maculipcnnis .
Fig. 29. — Head of female Acdes cinereus.
female Taeniorhynchus, Theobaldia, Culicelta, and Culex, the abdomen is blunt, and has short cerci (fig. 16). The claws of the fore- and mid-feet, too, are toothed in the three first-named genera (fig. 30) ; and those of the last four genera plain (fig. 31). As in the males of Aides and Ochlerotatus, the scaling of the head distinguishes also the females of these genera ; for broad, flat-lying scales nearly cover the crown in Ai'des, while in Ochlerotatus they are confined to small patches at the sides posteriorly (figs. 28, 29) ; and again, the brilliant, white, triangular, lateral, abdominal spots of Finlaya geniculates separate this species from the British species of Ochlerotatus, which have more
or less continuous pale abdominal bands (figs. 51-58). Taeniorhynchus, Theobaldia,and Culicella differ from Culex in the first hind-tarsal joint,
which is shorter than the hind tibia (fig. 24), while in Culex it is about as long or longer (fig. 32).
The fork, too, of longitudinal vein 2 in Culex is decidedly 1<
Fig. 30.— Claws of fore-foot of Ochlerotatits caspius female.
FlG. 31. — Claws of fore-foot of female Culicclta morsitan .
FlG. 32. — Hind-leg of Culex pip;
l'!''- 33~ Distal [>:irt of wing of and its stalk (that is, the part of the vein between the fork and the cross-veins) correspondingly short (fig. 1 » ; while both fork and stalk of longitudinal vein 2 in Taeniorhyncfius, Tkeobaltlia, and moderately long (fig. $$).
In Tfieobaldia, the cross-veins of the wing are nearly in a line
(fig. 33), the wings spotted, and the second abdominal segment has a median pale stripe (fig. 36) ; in Culicella, the posterior cross-vein is distant from the mid cross-vein not more than its own length (fig. 34), the wings are plain, and the second abdominal segment has no median pale stripe (fig. 37) ; while in TacuiorJiyiicJnts the posterior cross-vein
Fig. 34. — Cross-veins and parts of veins 2, 3, 4 and 5 in wing of Culicella morsitans.
Fig. 35. — Cross-veins and parts of veins 2, 3, 4 and 5 in wing of Taeniorhyn- chus richiardii.
FlG. 36. — Second abdominal segment of female Theobaldia annulata.
Fig. 37. — Second abdominal segment of female Culicella morsitans.
FlG. 38. — Scales from third longitudinal vein of wing of TacniorJiynchus richiardii.
Fig. 39.- — Scale from third longitudinal vein of wing of Culicella morsitans.
is distant at least its own length from the mid cross-vein (fig. 35), the wings are speckled with light and dark scales, and there is no median pale stripe. Besides, the wing-vein scales of Taeniorhynchus (especially the lateral wing- vein scales) are much wider than those of Theobaldia or Culicella (figs. 38, 39).
31
The following key summarises these female charact-
l'l MALES.1
A. Abdomen without scales (fig. 15 . Scutellum narrow and not
markedly trilobed fig. 42). Pali rly as 1 the
proboscis (fig. 27) ... . \. Anophel
B. Abdomen densely clothed with imbricating scale 16).
Scutellum markedly trilobed (fig. 22). Palps not one quarter the length of the proboscis (figs. 28, 29). ' I. Abdomen long-tapering and pointed (figs. 51-58 . Fore- and mid-feet with toothed claws (fig. 30). ( a. Flat-lying scales on crown of head mostly broad . . II. .
\ b. Flat-lying scales on crown of head all narrow.
( i. More or less complete pale abdominal bands ; ceni long \W.Ochlerotatus. \ ii. White, triangular, lateral abdominal spots ; cerci short IV. Fin lava. II. Abdomen slightly tapering and blunt (fig. 16). Fore- and mid-feet with untoothed claws (fig. 31).
a. First hind-tarsal joint shorter than the hind-tibia fig. 24 . Second longitudinal vein with moderately long stalk and fork (tig. 33).
' 1. Posterior cross-vein separated from, mid cross-vein by at least its own length (fig. 35). Wings speckled with dark and light scales. Wing scales broad (fig. 38 . Second segment of abdomen without pale median stripe ........ Y. Taeniorhynchus.
. Posterior cross-vein separated from mid cross-vein by less than its own length (fig. 34). Wings plain. Wing-scales narrow (fig. 39). Second segment of abdomen without pale median stripe (tig. 37) . VII. Culicella.
. Posterior cross-vein nearly in a line with mid cross- vein (fig. 33). Wings with spots. Wing-scales narrow. Second segment of abdomen with a median pale stripe (fig. 361 VI. Theobai
b. First hind-tarsal joint as long or longer than the hind- tibia .fig. 32 . Second longitudinal vein with long fork and very short stalk (fig. 1) . . . . .VIII. Culex.
C. Abdomen and scutellum as in B. Palps a little more than
one third the length of the proboscis (fig. 130) . . IX. O/t/io/
In addition to the points above mentioned, a character at the distal end of the hind-tibia is sometimes useful in distinguishing the genera, and is applicable to both sexes. In Ochlerotatus ami A for instance, there is a straight row of numerous bristles nearly at the apex of the hind-tibia. This is nut apparent in Cu/ex, Culicella Theobaldia.
Jee also c . • 1 1 -•
32
3. TO IDENTIFY THE SPECIES.
When the genus of a specimen has been determined, it is possible to go on to consider the particular species. There is only one British species in each of the genera Acdes, Taeniorhynchus, Finlaya, Theobaldia and Ortho-podomyia ; so that these genera do not at present concern us. On the other hand, Culicella and Culex each have two; Anopheles three, and Ochlerotatus eight, British species; and each of these genera will now be dealt with in turn.
&>
a. Anopheles.
Generally speaking, the three British species of Anopheles are easily distinguished, and it is only occasional specimens that give trouble. A . maculipennis is known at once by its spotted wings ; and A. plumbeus is smaller and darker than A. bifurcatus, besides having a blackish thorax and ashy-grey streaks, instead of the brown thorax with pale streaks of A. bifurcatus. In some characters (e.g., the breadth of the scales of the wings) A. bifurcatus is intermediate between A. maculipennis and A. plumbeus, so that doubtful specimens lie between A. maculipennis and A. bifurcatus on the one hand, and, on the other, between A. bifurcatus and A. plumbeus. Thus, the spots in A. maculipennis may be feebly developed, while the wing- scales of a specimen of A. bifurcatus may be particularly abundant, and tend to be massed at those parts of the wing where the aggregated scales of A. maculipennis form spots. (The same tendency may be observed in Culicella morsitans and C. fumipennis, thickly-scaled specimens of which show a tendency to a spotted condition, owing to the scales being more thickly crowded in places where in Theobaldia anuulata they are aggregated to form spots.) Or a small, dark specimen of Anopheles bifurcatus may appear very much like A. plumbeus. It is useful, therefore, to notice one or two other points of difference between the three species of Anopheles.
I. In the middle of the anterior end of the thorax, on its upper surface, is a tuft of thin, hair-like scales. In A. maculipennis these are straw-coloured, very thin, and tend to be somewhat loosely distributed (fig. 40;. 1 In A. bifurcatus and A. plumbeus they are decidedly whiter,
; In fig. 40 the scales are rather too closely aggregated.
broader, and more densely aggregated (fig. 41 >. In A. plumbeus they are even whiter in colour and broader than in A. bifurcates ; but the character of this scale-tuft is of more use in distinguishing A. maculi- pennis from A. bifurcates, than A. bifurcatus from A. plumbeus.
2. The posterior outline of the scutellum of A. maculipennis and A. bifurcatus is a fairly regular curve, convex posteriorly (fig. 42). In
FlG. 40. — Fore-part of thorax of Anopheles FlG. 41. — Fore-part of th
maculipennis , viewed from above and bifurcatus, viewed from al ! in
in front. front.
A. plumbeus it is somewhat flattened or even slightly concave at the sides (rig. 43). The whole scutellum is slighter in A. plumbeus, and. the median tubercle smaller and more compact. In A. maculipennis the median tubercle is more diffuse and swollen than in A. bifurcatus and the lateral tubercles smaller. But the characters of the scutellum
. 42. — Scutellum of Anop bifurcatus.
Fig. 43.
are more useful in distinguishing A. plumbeus from ./. bifurcatus than A. bifurcatus from A. maculipennis.
3. The male genitalia differ considerably in the three species, not only in the details of the smaller parts, but in the forceps them- selves. If one of the stout basal joints or side-pieces ol the forceps is isolated, besides the rather limp curved hairs with which especially
D
the distal end is plentifully provided, a single, straight, stiff bristle will be seen projecting from the inner edge of the side-piece ; and a pair of stouter bristles arise from the ventral surface of the side-piece near its base. In A. maculipennis and A. plumbeus (figs. 44 and 46) the single bristle springs from near the middle of the inner side ; and in A. bifurcatus (fig. 45) from near the apical end of the side-piece. In A. maculipennis the paired bristles (especially that on the inner side) are borne on a projection or lobe of the side-piece (fig. 44) ; in A. plumbeus they are inserted directly on the side-piece (fig. 46). In A. bifurcatus (fig. 45) the inner one is borne on a slight
Fig. 44. — Left forceps of Fig. 45. — Left forceps of Fig. 46. — Left forceps of
genitalia of Anophcks genitalia of Anopheles genitalia '[ of Anopheles
maculipennis, from be- bifurcatus, from beneath. plumbeus, from beneath, neath.
projection, but the outer one is directly inserted ; moreover, this outer bristle is double, flattened, and frayed distally into several branches.1 These differences may be tabulated as follows : —
Anopheles.
Obvious Characters— ' A. Wings spotted B. Wings plain.
/ I. Thorax brown, with pale longitudinal bands ; larger species ........
1 1. Thorax blackish, with ashy-grey longitudinal bands ;
1. A. maculiperuiis.
smaller species
2. A. bifurcatus.
3. A . plumbeus.
1 This has been noticed and figured by S. R. Christophers, 1915, Indian Journal of Medical Research, vol. iii., p. 378, pi. xx., fig. 1. Christophers, following Felt, calls the paired bristles " claspettes."
35
Less obvious Characters —
A. Wino-scales less crowded and narrower; hair-like scales
of thoracic tuft very narrow, less densely aggri tnd
straw-coloured (fig. 40); posterior outlin< utellum
forming an even curve: median tubercle of scutellum very diffuse and tumid ; lateral tubercles small . 1. A.maculip
B. Wing-scales more crowded and less narrow ; bair-like
scales of thoracic tuft not so narrow, more densely aggregated, and white (fig. 41 ; posterior outline of scutellum forming an even curve (fig. 4: ; median tubercle of scutellum tumid, but not so diffuse as in A. maculipennis ; and lateral tubercles larger . . 2. A. bij
C. Wing-scales more crowded and rather broad : hair-like
scales of thoracic tuft broad, more denser) aggregated, and white ; posterior outline of th( - ''Hum flattened, or even slightly concave, laterally (fig. 43: : median and lateral tubercles small and well-defined . . .3. A.plunv
Characters of the Male Genitalia — A. Single bristle is near the apical end of the side-piece. The inner one of the paired bristles carried on a small pro- jection : the outer inserted directly, double, flattened and much frayed distally (fig. 45) . . . . .2. A. bifurcatiis.
1 B. Single bristle is near the middle of the side-piece.
I. Paired bristles (especially the inner one) carried on
projections or lobes of the side-piece (fig. 44) 1. A. maculipennis. II. Paired bristles inserted directly on the side-piece
tig. 461 . . . . . . . .3. A.plnmbt
b. Ochlerotatus.
\
I
The eight British species of Ochlerotatus fall readily (for purpos of identification) into two groups, one (figs. 47 50), including 0. easpius, 0. curriei, 0. vexans, O. waterhousei and 0. annulipes, having white bands on the hind-tarsal joints ; and the- other, represented by the species 0. detritus, O. nemorosiis, 0. rustiats, having uniformly dark hind-tarsi. Apart from the white banding, the tarsi and le_;s genera in both groups may be speckled with light scales, giving a pepper- and-salt appearance to these structures ; and the wings in both groups may have dark scales only or with but very (c\v white sea (O. vexans in the first, and all except 0. detritus in the second grot; or may have mixed light and dark scales, so as g< nerally to ha\ a speckled look. The chief remaining characters for diagnosing the species are those exhibited by the abdominal pattern- 5
and the male genitalia (figs. 59 65).
D 2
3^
FlG. 47. — Right hind-leg of 0. caspius. Fig. 48. — Right hind-leg of 0. vexans.
FlG. 49. — Right hind-leg of 0. water Aottsei.1 Fig. 50. — Right hind-leg of 0. annulipes.
Fig. 51.— Abdomen Fig. 52. — Abdomen Fig. 53.— Abdomen Fig. 54. — Abdomen of female 0. cas- of female 0. of female O. water- of female 0. annu- pins. vexans. housei, //pes.
1 The sprinkling of dark scales on the proximal and ventral parts of the femur should be a little more pronounced in fig. 49.
In the first group, O. Crispins and 0. curriei arc at on< vn by
the white bands embracing the distal end of one tarsal ; the
proximal end of the next (fig. 47). In the other speci< band occupies only the proximal end of each joint. O. caspi easily recognised by the bright chestnut-orange colour of the th with whitish stripes, and by the same sharply-contrasted ci on
the crown of the head. Thus, even a very much rubbed specimen m
V
.K?
I
,
! 55. — Abdomen Fig. ^,6. — Abdomen Fig. 57. Abdomen Fig. 5S.—
of female O. of female O. nemo- female O. >v.
detritus. ro.'
often be identified with certainty. 0. curriei, on the other hand, has the top of the thorax dullish brown, with a pale band <>n each side. O. caspi/ts has broad, mixed light and dark scales on the win: the male genitalia are shown in fig. 59 ; while (\ curri i ha- 1 wing-scales, and the scales on longitudinal veins 3 and 5. and en the forks of 4, are mostly dark.
In O. vexans the white bands at the proximal en the tai
joints are very narrow (fig. 48) ; while in 1
Fig. 59. — Genitalia of male Ochlerotatus caspius. a.l. Apical lobe. b.l. Basal lobe. c. Clasper. cl. Claw. h. Harpe. ho. Harpago. s. Side-piece.
Fig. 60. — Genitalia of male 0. ve.xans. ho. Harpago.
Fig. 61. — Genitalia of male 0. waterhousei. FlG. 62.— Genitalia of male 0. annidipes.
FlG. 63. — Genitalia of male 0. detritus.
Fig. 64. — Genitalia of male 0. nernoro
1 1 . 65. — Genitalia of male 0.
. — ( lenitalia
40
G. annulipes (fig'. 50) the bands of the last four tarsal joints are wide, occupying nearly half the joint in the latter, and about a third in the former species. 0. vexans^ too, has only dark scales on the wings, while the wings of the other two species have the pepper-and-salt appearance due to a mixture of light and dark scales. Its genitalia, too, have a remarkable form (fig. 60). Again, the undulating posterior border of the pale abdominal bands is character- istic of O. vexans (fig. 52).
O. waterkousei and 0. annulipes are not so easy to distinguish. The males are best distinguished by the genitalia, which are markedly distinct (figs. 61 and 62). And there is a difference in the coloration of the thoracic scales of the females, though it is not easy of application (see F. W. Edwards, 191 2, The Entomologist, vol. xlv., p. 194). In both, the ground-colour of the thoracic scaling is deep golden brown, and on this there are pale longitudinal markings of a brassy colour. In the females of 0. annulipes the ground-colour is richer, and the lighter brassy lines yellower and brighter ; so that the thorax of ( '. annulipes looks yellower and that of O. waterkousei browner. But the best general characters are in the hind-femur, and in the pattern beneath the abdominal segments. The outer surface of the hind-femur is fairly evenly sprinkled with dark scales in O. waterkousei (fig. 49), though proximally and ventrally they are not so numerous as distally and dorsally. The outer side of the hind-femur of 0. annulipes is similar distally and dorsally, but proximally and ventrally it is almost destitute of dark scales (fig. 50). This difference is more pronounced in the females than in the males. On the under- side of the abdomen of O. annulipes the dark markings form a continuous median stripe with slight lateral projections ; while in O. waterkousei they form transverse stripes, and the median stripe is generally obscure or absent. The proboscis, also, in O. annulipes is yellow on the underside except at the base and tip ; while in 0. water- kousei it is merely pale.
In the second group O. detritus is unique for having mixed light and dark scales on the wings (figs. 67 and 68). Otherwise it very closely resembles O. nemorosus (which may have some white scales on the sub-costal vein), but there is generally a sprinkling of white scales on the dark portions of the abdomen above (fig. 55), and the
4 J
legs are more plentifully sprinkled with white scales than I nemorosus ; moreover, the male may be known by its genita
In 0. detritus, 0. nemorosus, and O. rusticus, the abdom< n is .irk above, with more or less continuous transverse pale bar the
proximal end of each segment. As has already been O. detritus may be known from the other two s by the pale-
scales on the wings as well as by the sprinkling of pali the
dark parts of the abdomen. 0. nemorosus differs from I chiefly in the paler, almost white tint of the abdomin and
their tendency to widen laterally rather than in the mid-lin In O. rusticus, the pale abdominal bands are yellower, and, in the female, tend to widen medianly to form a continuous line I t; In
the male this median line appears only on the second nent.
The male genitalia are shown in fig. 65 ; and even to the 0. rustic us may be distinguished by the dense clothing of hairs
on the side-pieces.
Fig. 67. — Stalk of fork of second Ions', vein of Ochlerotatus detritus.
of fork o! long, vein in Ochlerotatus >.
The following tables summarise these differed
Ochlerotatus. — General characters.
A. Hind-tarsi with pale bands. t I. I 'ale bands embrace ends of contiguous tarsal join!
Tale bands on abdomen overlap the junctions of the segments and are continuous with a median longitudinal band (fig. 5 1 . a. Wings speckled with broad, light and dark
bright cliestnut-orange with pale longitudinal mark 1 . Wing scales narrower, wings speckled, but
and fifth, and forks of fourth chief!)
dark; top of thorax brown in the n tnd pal<
the sides .....-•■
.
42
II. Pale bands only at proximal ends of tarsal joints (figs. 48-
50). Pale bands of abdomen chiefly at proximal ends of
abdominal segments, and no median abdominal stripe
(figs. 52-54).
'a. Tarsal pale bands very narrow (fig. 48). Only dark scales
on the wings ....... 3-0. vexans.
/>. Tarsal pale bands occupying one third to half of each tarsal joint, except the first (figs. 49, 50). Wings speckled with light and dark scales.
1. Outer side of hind-femur sprinkled with black scales on the proximal and ventral part (fig. 49). Pale markings on thorax whitish in female. Basal lobe of side-piece in male with a tuft of strong bristles basally, and a long, hairy, lobe-like basal extension (fig. 61). Proboscis in both sexes pale beneath in the middle ........ 4. O. ivatcrhousei.
2. < Hiter side of hind-femur without black scales on the proximal and ventral part (fig. 50). Pale markings on thorax of female bright yellowish. Basal lobe of side-piece in male without a tuft of strong bristles, and without a long, hairy lobe-like extension
rig. 62). Proboscis of both sexes yellow beneath in the middle ....... 5. O. aniutlipcs.
B. Hind-tarsi entirely dark.
I. Wings speckled with light and dark scales (fig. 67). Dark portions of abdominal segments sprinkled with white scales (fig. 55) ...... 6. O. detritus.
II. Wings with dark scales only (fig. 68) — a few light scales on the sub-costal vein in V. ncmorosus — ' a. Abdominal bands whitish, widening laterally, but not
medianly (fig. 56) ..... 7. O. nemorosus.
/. Abdominal bands yellowish, widening medianly in the female, so as to tend to form a pale median line tig. 57). In the male a median line only on segment 2. The genitalia are very hairy (fig. 65) ... S. O. msticus.
W
\
2. Ochlerotatus and Finlaya. — Male genitalia (figs. 59-66).
The most obvious structures of the male genitalia of Ochlerotatus are the proximal joints of the outermost pair of grasping organs, or forceps. Each of these large proximal joints, or side-pieces (fig. 59, s.) has hinged to its distal end a more or less slender hook, the clasper (fig. 59, c), which itself is terminated by a thin claw (fig. 59, ci). On the inner side, each side-piece is more or less divided- longitudinally into a dorsal and ventral flap. The dorsal flap generally has a more or less straight edge, but the ventral flap generally has pronounced apical (fig. 59, a.l.) and basal lobes (fig. 59, b.l). The apical lobe is
r3
Ki v to Male Genitalia in British Spe< ies 01 Ochlerotatus and Finldya.
A. Claspcr much flattened and becoming wider distally : apical
lobe very small ; basal lobe very wide and projecting but little. Harpago with somewhat globular apex . . 3.
B. Clasper narrow and tapering distally ; apical joint of harp, 1
more or less strap-shaped or expanded, but never globuli I. Outer and inner edges of side-pieces nearly parallel, and strongly and regularly curved, the whole side-piei narrow and forming the arc of a circle ; apical lobe ventral flap hardly existent; only the distal part of the basal lobe developed, and this is prolonged into a narrow arm-like projection with expanded hand-like end ; the bristles of the tuft at the base of the basal lobe are ex- ceedingly long, and extend along the ^dge of the ventral flap as a dense fringe of very long hairs ; claw of clasper undulating; distal joint of harpago spatulate . . O.rusticu
II. Outer edge of side-piece neirly straight or slightly curved ; inner edge of dorsal flap more or less undulating ; lobes of ventral flap variously developed.
Apical lobe of ventral flap very slightly developed : distal joint of harpago strap-shaped.
1. Basal lobe of ventral flap projecting abruptly and bear- ing a few specially large bristles basally ; three small notches on outer side, and one on inner side of clasper, near its tip — a hair springs from each . I. O. casj,
2. Basal lobe of ventral flpp forming but a slight, rounded prominence, and has no specially large basal hairs ; clasper without any hair-bearing notches near its tip, or with but one .... 9. Finlaya geniculata (fig. 66).
b. Apical lobe of ventral flap prominently developed, even if small ; basal lobe abruptly prominent. 1. Basal lobe carried on a broad base ; near the tip of the clasper, and on its outside, four or rive little hair- bearing notches— on the inside, none ; distal joint ( of harpago strap-shaped ; one large bristle at base
of basal lobe ~. U. >:
Basal lobe, if prominent, carried on a comparatively
narrow base and more or less conical in shape. a. Edge of dorsal flap sharply undulating ; basal lobe not prominent, and not distally produced; distal joint of harpago flattened, about twice as loi wide, with a rather narrow, delicate, rounded, selvedge-like expansion ... 5. 0. ami:,.
ti. Edge of dorsal flap nearly straight; basal lobe with a prominent tuft of long bristles, and distally drawn out into a spatulate expansion ; distal joint of harpago not much flattened, but with a very deli- cate flag-like expansion on one side • 4- O. a ■y. Hdge of dorsal flap nearl) straight : a few extra- large bristles at proximal end of the basal lobe ; no apical extension of basal lobe, distal jo harpago strap-shaped ....
44
generally covered with short, small hairs ; but the basal lobe, as a rule, has a tuft of long, stiff bristles at its base, and, distally, is covered with little mammilliform projections, each of which bears a small, but stiff, hair. The dorsal flap of the side-piece is covered with very long coarse hairs, and often with a fair sprinkling of scales.
Between the side-pieces, and about a half as long as them, is another pair of hook-like structures, the harpagones* (fig. 59, 60 ho). Each harpago has a rod-like, more or less curved, basal joint, and a limp, hook-like, distal joint, which may be much flattened or expanded. A third and fourth pair of hook-like organs, the harpes (fig. 59, Ji) and unci lie within the harpagones. Each harpe is more basally placed than the corresponding harpago of each side, and consequently, though nearly as long, does not project nearly as far. Their shape varies but little in Ochlerotatus.
69
FlG. 69. — Proboscis of female Culicella mors 1 'tans.
FlG. 70. — Proboscis of female Culicella fumipennis .
c. Culicella.
Culicella morsitans and C. fumipennis are nearly alike ; in fact, the flies of the two species are very difficult to distinguish in both sexes. The larvae, however, are quite distinct. The proboscis in both species is black, but the female of C fumipennis has a few white scales on the proboscis, especially at the sides (figs. 69 and 70).'- The males may be distinguished by the comparative length of the first fore-tarsal joint and the remaining four joints. In C. morsitans the first fore-tarsal joint is decidedly longer than the remaining four joints, while in C fumipennis it is about as long. (See F. W. Edwards, 19 12, The Entomologist, vol. xlv., pp. 261-2.) In practice, however, I have
1 These structures have often been termed "harpes "in descriptions, and vice versa, the harpes have been termed "harpagones."
2 These differences are somewhat exaggerated in the figures.
found this test hard of application, owing to the difficull uring
no fore-shortening of these structures in viewing them. The side of the abdomen of both sexes al ts a diflfei i
fumipennis (fig. 72) the lower side of the mure distal segments of I abdomen, especially segments six and seven, have a well-defin pattern of darker scales upon a light background. 1 he lighter form a pair of triangular patches at the base of the segment, and th< is a median triangular patch at the apex of the segment. In morsitans (fig. 71) the lighter scales arc s< tl d more irregularly over the segment beneath, and there is only a tendency to the pattern formed in C fumipennis} This is specially marked in segment six.
' {!<-. ■
V
' * .. I
FlG. 71. — Underside of sixth abdominal segment of male Culicclla mors it,:
72. — Underside of sixth abdominal segment of ma
Culicclla fumipennis.
Key to the Gi 'ulicella.
1 - per surf;,
sixth abdominal segment of female (
A. In female, proboscis black (fig. 69) with no -ibly om
two white scales at sides. In male, first fore-tarsal joii decidedly longer than the remaining four joints ; segments four to seven of the abdomen (especially segment six ben< with a diffuse pattern, chiefly of lighter scale 1 .
!'.. In female, proboscis blackwith a few whit< at the si
(fig. 70). In male, first fore-tarsal joint is hardly longer than the remaining four joints ; segments six and seven ol abdomen especially segment six) beneath with a clear pattern of lighter and darker scales (fig. 72 ...
('. Culex. Onlv one specimen of Culex apicalis has been taken in Britain. But since this is an authentic capture (the specimen i> in the museum of Cambridge University), ami there are no obvious circun pointing to its introduction, the species must be regarded as Brit and a comparison made with Culex pipiens, the Common Gnat.
1 These difference- are somewhat i ted in ih
46
The transverse pale bands on the abdomen of Citlcx pipiciis are basal (fig. 1 6), while those of C. apicalis are apical (fig. J$). They are cream-coloured in C. pipiens and whitish in C. apicalis. The general coloration of C. pipiciis is a rich golden brown, while that of C. apicalis is a very dark grey. It is hardly necessary to put these three diagnostic characters in a tabular form.
*t>*
B. THE LARVA.
i. TO IDENTIFY THE GENERA.1
It is not possible in the present state of our knowledge to make a complete scheme for the identification of the pupae of British Mosquitoes. Doubtless in time this could be accomplished, and already some distinctions have been published (e.g., F. V. Theobald, 1901, A Monograph of the Culicidae or Mosquitoes, vol. i., pp. 51-2). But generally the differences are not readily seen, and often would be extremely minute. Moreover, for the practical purposes of identifi- cation, there is comparatively little loss in being unable to identify a pupa. For where pupae are found, larvae, as a rule, are also abundant; and, since the pupal instar persists but a few days, it is often possible to keep the pupa and thus rear the fly. The distinctions, therefore, of the larvae will be next considered.
Aia phc/cs-\ax\-3.Q may at once be known by the absence of a siphon (figs. 10 and 11). Their tracheae open by a pair of spiracles, or stig- mata dorsally placed on the eighth segment, and nearly flush with the general surface. In all the other genera — called collectively Culicines -the spiracles are borne on the end of a long, straight, horn-like prominence of the eighth segment, the siphon, heavily chitinised in all instar except the first. When a larva is at rest just beneath the surface-film, the horizontal position distinguishes Anopheles from a Culicine ; the latter hangs from the surface by its siphon at an angle of about 45 degrees. When disturbed, A ?wp/ie/es-\a.rva.e jerk themselves backwards with great swiftness, and slowly sink ; while Culicine larvae jerkily wriggle directly towards the bottom.
Taeniorhyuchus has a siphon curiously modified for piercing the stems of aquatic plants. It is wide proximally, but suddenly narrows into a long tapering point. There is no pecten (fig. 74).
1 The diagnostic characters do not necessarily hold outside British species.
\7
Fig. 74. — Siphon of 7 aeniorhynchus richiardii. Fig. 75. — Siphon of
Fig. 76. — Siphon of Theobaldia annulate } ~ Siphon of
48
podomyia has a normal siphon, but no pecten (fig. 152, p. 1 1 1).
Aedes, Ochlerotatits, Finlaya, Theobaldia, and Culicella have a single
pair of tufted hairs on the siphon {Ocfilerotatus rusticus has a second
Siphoi • - ■
Fig. 70. — Siphoi
minute tufted hair), while O/A-.r (rig. ;o> has several such hairs in scattered positions on the very slender siphon.
In Aides (fig the siphon is comparatively slender, nearly four
times as long as wide ; the pecten extends to about the middle of the siphon, and the few most distal teeth are separated by wide gaps.
The tufted hair lies in a line with the pecten, between tl th
and the distal end of the siphon, and, consequently, con beyond the middle of the siphon. The scales of the comb 1 it- transverse line.
In Ochlerotatus and Finlaya (figs. 105 1221 the siphon is con tively stout, not more than thrice as Ion • ; the pecten
not extend as far as the middle of the siphon, except in ( and O. rustiais ; and the tufted hair lies near the distal end of the pecten, either in a line with it or just ventral to it. The antennae the larval Finlaya are without the appressed spines that are over the antennae in Ochlerotatus (fig. 1 04).
In Theobaldia (fig. 76,1 and Culicella (figs. 77-8) the tufted hair '. ventral to the pecten near its proximal end. In Theobaldia the siphon is stout, and the pecten-teeth end in long hair-like threads. In Culicella the siphon is very slender and the pecten-teeth normal.
In addition to the above characters, Mr. F. W. Edwards has pointed out to me that the hairs of the second pair above the anus are tufted in the genera TacniorhyncJuts, Theobaldia, and Culicella, like those of the first pair ; but simple in Aides, Ochlerotatus, and Fiula In Culex they are bifid.
Key ro Genera of Larva .
A. Siphon absent 'fig. 10 . . . . . I. A>;
B. Siphon present.
. I. Pecten absent. Siphon short with wide base and pointed
apex 1 fig. 74 .... V. Taen
II. Pecten present. Siphon more or less cylindrical, tapering
somewhat di stall y. fa. Siphon with a single pair of tufted hairs (a. second
minute pair in Ochlerotatus ntsticio , or <»f simple hairs in the first instar. ' 1. Tufted hair near the distal end of the ;
iphon slender ; tufted hair well beyond the middle of the siphon ; pecten extending t'j about the middle of the siphon ; the last :i-teeth
widely spaced . • ■ • • II.
■i. Siphon stout ; tufted hair general': die
1 of the siphon, and the pecten ni the
middle: if the tufted hair »nd the
middle, the last few widely-spaced than the r* 105- 12.
$ i. Antennae with scattered a] • I-'
J Antennae without scattered apj
E
;o
2. Tufted hair near the proximal end of the pecten, or about at the middle of the pecten in the first larval instar. fa. Siphon stout ; pecten-teeth drawn out terminally into
long hair-like filaments (rig. 76) .... VI. Theobaldia. I ;i. Siphon slender ; pecten-teeth normal (figs. 77-78) . VII. Culicclla. Siphon with several pairs of tufted hairs (of simple hairs
in the first instar) (figs. 79, 126-8) . . . . VIII. Culcx.
III. Pecten absent. Siphon as in II. In fourth instar, abdominal segments 7 and 8 with heavily chitinised V dorsal plates (fig. 132) . . . . . IX. Orthopodomyia.
2. TO IDENTIFY THE DIFFERENT SPECIES AND (AS FAR AS THEY ARE KNOWN) THE DIFFERENT INSTAR OF EACH SPECIES.
a. Anopheles.
a. The Fourth (last) Larval Instar.
In A. maculipennis and A. bifurcatus (figs. 80, 81) the six post- antennal hairs are large and pinnately branched, while in A. plumbe?is (fig. 82) they are very small, and simple. In A. plumbeus the anterior clypeal hairs are simple, or nearly so. In A. bifurcatus they are simple, or, at most, split at the ends into two or three branches. In A. maculipennis, the outer hair, lying over the brush, is branched repeatedly, while the inner hair has a few branches arranged pinnately.
The palp in all three species bears a branched hair near the apex, apically and internally a pair of small, sub-equal spines, and apically and externally a second pair of spines, which in A. plumbeus are sub- equal, but unequal in the other two species, especially in A. bifurcatus. The apex of the palp also bears three chitinous laminae, which are very thin and exceedingly difficult to see at their distal ends.
The float-hairs of A. maculipoinis have about twenty-two leaflets, with their bases arranged on an elongate capitulum, which is sessile or with a short, thick stalk. In A. bifurcatus the leaflets are about sixteen in number, and are inserted on a more club-shaped capitulum with a more slender stalk. In A. plumbeus about fourteen leaflets are crowded at the apical end of a club-shaped capitulum with a rather thick stalk.
The antenna of A. maculipennis and A. bifurcatus has a branched hair towards the base in the former, and near the base in the latter
species. In A. plumbeus this hair is simple, and. nearer the middle of the antenna which is short and has no scattered hairs (figs. 80-82 >. The comb of A. maculipennis (fig. S$) has about twenty-six to
Fig. 80.— Head of fourth Fig. 8 1.— Head of fourth I ; . 82.— Head of fourth
larval instar of A. macu larval instar of A. bifur- larval instar o( .!.
fcjini-. catus.
thirty teeth of at least three sizes ; about seven large, and betv each of these one or two of medium size, and between each medium-
1 2
52
sized tooth one or two small teeth. In A. bifurcatus (fig. 84) the comb has about twenty to twenty-five teeth in all, of which about ten are large, and between each of these one or two smaller teeth. But the difference in size between the larger and smaller teeth of A. bifurcatus is less than that between the larger and medium teeth of A. maculi- pennis. In A. plumbeus (fig. 85) the comb consists of about sixteen teeth, most of which are large, but a few slightly smaller ones occasionally occur.
Fig. 83. — Comb of fourth larval instar of A. maculi- pennis.
Fig. 84. — Comb of fourth larval instar of A. bifur- catus.
Fig. 85. — Comb of fourth larval instar of A. plum- beus.
/3. The Third Larval Instar.
The differences between the three species shown by the anterior clypeal and post-antennal hairs are the same in the third larval instar, except that in A. plumbeus the anterior hairs are more branched than in the fourth instar (figs. 86, 87, 88).
The palps of the third larval instar resemble those of the fourth instar, but the hair towards the apex of the palp of the third instar, A. plumbeus, is simple, or almost so.
The float-hairs of the third larval instar show differences similar to
those of the fourth instar, but they have fewer leaflets throughout than
those of the fourth larval instar.
The antennae of the third instar are similar to those of the fourth instar.
The comb of the third instar, A. maculipoinis, has about sixteen teeth in all ; generally seven larger teeth, and between them oni two considerably smaller teeth, which, however, vary somewhat in
Fig. 86.— Head of third Fit;. 88.— Head of third FlG. 87.— Head of third larval instar of A. maculi- larval inst.ir of A. plum- larval in>tar of ./.
pennis. kits.
size (fig. 89). In A. bifurcatus there are about eighteen teeth ; eight or ten large teeth, and between them an occasional and somewhat smaller one (fig. 90). In A. plumbeus, the comb consists of about twelve sub-equal teeth (^fig. 91).
7. The Second Larval [nstar.
The second larval instar in all three species may be known from the third and fourth by the palp, which has no sub-apical hair. The
ie difference
1
The
-
The comb of ^4. «ra r seven large teeth, and
teeth between each large on- there are also six c . larger teeth alt- a ith
-
V
•
4
-
E -Head 94. — B :
larval .: ■ - larv:
as ma the difference in the size of the
jd than it is in A - fig. 96). In
:hs there are about ten sub-equal teeth {fig. o"
8. The First Larval Instar.
The first larval instar of A. maculipennis, A. bifurcatus, an pliimbeus so closely resemble one another that they arc not easy to distinguish. In all three species the first diners very considerably fn >m the second instar. All hairs of the head above are simple, except that one or more of the post-antennal hairs may be forked in the first
\VV
Fig. 95. — Comb of second Fig. 96. — Comb of second 1 J -Comb of second
larval instar of A. maculi- larval instar of ./. bifur- larval instar
■'"/'->"• caius.
two species ; in some specimens of A. maculipennis one or both of the outer anterior pair is forked (figs. 98, 991; and in A. plumbeus all the anterior clypeal hairs are more or less branched (fig. 99a). The float-hairs have but a single leaflet. The comb (figs. ioo. 101. 101a) has no alternation of teeth of different sizes, though they graduate some- what in size from the middle towards the dorsal end, and considerably
Fn;. 98. — Head of first Fn;. 99. Ilea . 99a. — Head ol
larval instar of .-/. macu larval instar of. .' larval instar of A.
from the middle towards the ventral end. The number of teeth varies considerably in different specimens, so that in any individual it is not safe to use the number as diagnostic of the species ; but generally there are six in A. maculipennis and eight in A. bifurcatus, but vary from five to nine in A. maculipennis and from eight to ten in A. bifurcatus ; and there are about seven in A. plum
1 The large bifurcate (n te) hair lying <>ut>ide the antenna ha> I
omitted.
56
second comb-like arrangement of teeth lying rather anterior and ventral to the primary comb. There are generally five teeth in this secondary comb, but the number varies considerably in different individuals. One or two of the teeth are often of a minute size compared with the rest, which are approximately equal in size
101 a
Fig. ioo. — Primary and secondary comb Fig. ioi. — Primary and secondary comb
of first larval instar of A. maailipennis. of first larval instar of A. bifurcatus.
Fig. ioia. — Primary and secondary comb of first larval instar of A. fihtmbeus.
Fig. 102. — Appressed bristles on ventral surface of ninth abdominal segment of first larval instar of A. tnaculipennis .
Fig. 103. — Appressed bristles on ventral surface of ninth abdominal segment of first larval instar of A.
bifurcatus.
Fig. 103a. — Appressed bristles on ventral surface of ninth abdominal segment of first larval instar of A, plumbcus.
1
(rigs. 100-ioia). A good character (besides the sub-antennal hair)
for the first instar of the three species is that of the appressed bristles that lie on the ventral side of the ninth (last) abdominal segment ; they form a wider group, and there are four or five larger
pairs in A. bifurcatus ; while in A. maculipennis they form a narrower group, and there are only about three larger pairs | figs. 102 - 103) ; and in A. plumbeus, the group is very narrow indeed, has feu- bristles and has only two larger pairs (fig. 103a).
Key to rui. Larvae of the British Species of Anophel
A. The six post-antenna] hairs are prominent.
I. The six post-antennal hairs arc pinnately-branched ; fin
of ninth segment present.
a. Outer anterior clypeal hair dendroid in shape ; leaflet - float-hairs spring from an elongate capitulum which sessile, or has a very wide stalk ; the difference in size between the larger and smaller teeth of the comb con- siderable ; smaller bristle of the outer pair at the apical end of the palp about three-quarters the length of the larger one 1. A. maculipennis.
Palp of maxilla with a sub-apical branched hair. a. 25-30 teeth in comb ; three, four or even five secondary and tertiary teeth between each of t lit- seven primary teeth ; about 22 leaflets in each float- hair (figs. 80, 83) . . A. maculipennis, fourth larval instar. \ #. About 16 teeth in comb ; one or two secondarv. and sometimes tertiary teeth between each of the seven primary teeth ; about 14 leaflets in each float- hair (figs. 86, 89) . . A. maculipennis, third larval instar. Palp of maxilla without a sub-apical hair; one or two secondary teeth between each of the seven primary teeth of the comb (figs. 92, 95) A. maculipennis, second larval instar.
b. Outer anterior clypeal hair simple, or once or twice split at the end ; leaflets of float-hairs spring from a clavate capitulum which has a short narrow stalk : the difference in size between the larger and smaller teeth of the comb is but slight ; smaller bristle of the outer pair at the apical end of the palp about half the length of the larger one . • . . • . . • 2. A. bifurcatus.
1 1. Palp of maxilla with a sub-apical branched hair.
a. About 25 teeth in comb ; one or two secondarv teeth between each of the ten primary teeth ; about 16 leaflets in each float-hair tigs. 81, 84) / A. bifurcatus, fourth larval ins
( ,± About 18 teeth in comb ; one or two secondary teeth between each of the eight primary teeth : about 10 leaflets in each float-hair fij A. bifurcatus, third larval ii
Palp of maxilla without a sub-apical hair : about 14 teeth in the comb, alternately larger and smaller
s. 93, 96) .... A. bifurcatu s, second larval instar.
58
II. The six post-antennal hairs simple, or, at most, forked ; a bunch of appressed bristles occupies the place of the fin of the ninth segment ; a secondary comb present.
a. About 6 teeth in primary comb ; appressed bristles form a narrower group, and there are about three pairs of larger bristles (figs. 98, 100, 102) A. maculipennis, first larval instar.
b. About 8 teeth in primary comb ; appressed bristles form a broader group, and there are about five pairs of larger bristles (figs. 99, 101, 103) . A. bifurcatus, first larval instar.
B. The six post-antennal hairs are very small . . . .3. A.plumbeus.
I. Ninth abdominal segment with a fin. ( a. Maxillary palp wiih a sub-apical hair.
( 1. All four anterior clypeal hairs simple or merely split once or twice ; sub-apical hair of palp freely branched ; about 16 teeth in the comb (figs. 82, 85) . A.plumbeus, fourth larval instar. / 2. All four anterior clypeal hairs freely split, especially the inner pair ; sub-apical hair of palp simple or merely split at the end ; about 12 teeth in the comb (figs. 88, 91) .... A.plumbeus, third larval instar.
b. Maxillary palp without a sub-apical hair ; outer pair of anterior clypeal hairs twice forked, inner pair pinnately branched ; about 10 teeth in comb (figs. 94, 97)
A. plumbeus, second larval instar.
II. A bunch of appressed bristles occupies the place of the fin of the ninth segment ; a secondary comb present (figs. 99a, 101a, 103a) ...... A. filumbeus, first larval instar.
b. Oclrferotatus.
It is unfortunate that the Museum Collection contains no larvae of Aedes cii/ercus, except in the fourth instar. The younger stages of this species, therefore, have yet to be described. The next genus is Ochlerotatus, with its eight British species ; and the differences between the species, and, where known, between the different larval instar, will now be considered. The first instar of all the species (as far as it is known, see figs. 108, 116) can be distinguished from the succeeding instar by the following characters. There is no fin on the ninth segment ; only the distal part of the siphon is heavily chitinised ; the pecten has but six teeth, most of which are very wide, and with the main denticle not very much larger than the rest ; the tufted hair of the later instar is represented by a simple hair ; the scales of the comb form a single row ; there is an egg-breaking tooth on the upper
59
surface of the head ; all the post-antennal hairs lie approximately in a slightly-curved line, and the pre-antennal hairs arc apparently absent. In the second to fourth instar there is a fin on the ninth segment ; the whole, or the greater part, of the siphon is heavily chitinised ; the pecten has more than sixth teeth, of which the main denticle is so much larger than the rest that it forms the greater part of the tooth; the tufted-hair of the siphon has from two to six or more branches; the scales of the comb form more than one row, or are irregularly arranged ; there is no egg-breaking tooth on the upper surface of the head ; the mid post-antennal hair has shifted forward and inward, and so comes to lie directly in front of the inner post- antennal hair ; and the pre-antennal hair is present and often highly- branched, but minute.
It is thus more easy to distinguish the first instar from the succeeding instar than to distinguish one species from another. Therefore, it is convenient to consider first the differences between the species in their second, third, and fourth larval instar, and then again in their first instar. With regard, then, to the second, third, and fourth larval instar, O.rusticus (fig. 112) and O.vexans (fig. icoj can be separated from the remaining five species with no difficulty, by their having the last one or two teeth of the pecten widely separated from the rest of the pecten and from each other. (The last tooth is slightly separated from the rest of the pecten as an occasional variation in other species of Ochlerotatus, especially 0. caspius.) 0. rusticus (fig. 112) has, moreover, three or four pairs of long simple hairs on the dorsal surface of the siphon, a second tufted-hair dorsal to, and about mid-way down the pecten, and the main tufted-hair decidedly ventrally with regard to the pecten. The second and third instar of O. rusticus and I . ins have not been 1 ibserved — moreover, the larval characters of 0. vexans have been taken from the figure in Dyar, Howard and Knab (1912, The Mosquitoes of North and Central America, vol. ii., pi. lxvi.) of O. sylvestris, which is n considered to be the same species as the European 0.
The larvae of the six remaining species are much more difficult distinguish. 0. detritus is perhaps the m I ited owin§
the anal gills which are very short and nearly -lobular, and the blunt comb-scales which are merely fringed and have not a lai
6o
terminal spine (figs. 121, 122). It requires, however, a high magnifying power to see this clearly. The conspicuously paler bases of the antennae in the fourth instar and the pecten-teeth with their com- paratively small, evenly graded denticles (figs. 121, 122) are also
Fig. 104. — Antenna of Finlaya geiticulata.
TEFIZI—,
Vic. 105. — Siphon, pecten-teeth, and comb- scale of O. caspins, fourth larval instar.
Fig. 106. — Siphon, pecten-teeth, and comb- scale of O. casfiius, third larval instar.
characteristic. The differences between the second, third, and fourth instar of 0. detritus (and this is applicable to other species as well) are seen in the numbers of the pecten-teeth and comb-scales, and in the greater complexity of the post-antennal hairs and tufted-hair of the
6i
siphon. But since these numbers and this complexity ha. considerable range of individual variation, the characb not strictly diagnostic, but should be applied with the i
FIG. 107. — Siphon, pecten-teeth, and comb- FlG. 108.— Siphon, pecten-teeth, and 1 scale of O. caspius, second larval instai scale of 0. caspitts, first larval instar.
FlG. 109. — Siphon of O. vexans, fourth larval instar (after Dyar, Howard and Knab, as Aides is).
110. — Siphon, pecten-teeth, a: scale of t' instar.
that in any one specimen any character may vary beyond the prescribed limits. With this caution, it may be said that the third instar of 0. detritus has ten to fourteen pecten-teeth, two or three
62
branches in the tufted hair, three or four branches in the outer post- antennal hair, and the other post-antennal hairs simple ; while the fourth instar has eighteen to thirty pecten-teeth, four to nine branches in the tufted hair, more than four branches in the outer post-antennal hair, and the inner with two branches.
FlG. hi. — Siphon, pecten-teeth, and comb- scale of O. annulipes, fourth larval instar.
Fig. 112. — Siphon, pecten-teeth, and comb- scale of O. nistiats, fourth larval instar.
No satisfactory difference has yet been found between the larvae of O. caspius and O. curriei. The shape of the comb-scales and pecten-teeth shown in figs. 105-107, 113-115, iio-in, are the best means of distinguishing O. caspius, O. nemorosus, 0. waterJiousei, and O. annulipes. In O. nemorosus the terminal spine of the comb-scales
is very large indeed, and the lateral spines form merely fringing bristles (figs. 113-115) ; in the other three species the terminal spine (or, in O. caspius two or three spines) is the largest, but not so much larger than the lateral spines. There are comparatively few denticles in the pecten-teeth of O. caspius (tigs. 105 107), and 0. annulipes (figs. 1 10-11 1), while there are many in those of O <tsei.1
FlG. 113. — Siphon, pecten-teeth. an 1 comb- scale of O.nemorosu s, fourth larval instar.
114. — Siphon, p le of c '. n . third larval insl
The antennae are conspicuously paler at the base in the fourth instar of O. caspius, less so in O. waterhousei and 0. annulipes, and uniformly pigmented in 0. nemorosus. Generally, in 0. caspius
the tufted hair lies decidedly beyond the middle of the pecten. In O. nemorosus the anal gills are large and generally lunger than the segment.
1 The examination of more material has shown that ihe> and a satisfactory distinguishing character for larvae of 0 am
yet to be found.
64
The second and third instar of 0. waterhousei and 0. annulipes have not been examined, but the earlier stages of 0. caspius and 0. nemorosus are known (figs. 106-107, n4-n5)- The pecten-teeth number nine to thirteen, fourteen to seventeen, and nineteen to twenty- six in the second, third, and fourth instar of 0. caspius, and twelve to fourteen, twelve to sixteen, and eighteen to twenty-six in 0. nemorosus ; the tufted hair has three to four, four to five, and five to six branches in 0. caspius, and two to three, three to five, and four to six in 0. nemorosus ; the outer post-antennal hair has two, five, and eight branches in 0. caspius, and two, three, and five to eight in 0. nemorosus ; the mid-hair is simple in all instar of both species, except the fourth, of 0. nemorosus, when it generally has two branches ; the inner hair has
"^^
FlG. 115. — Siphon, pecten-teeth, and comb- scale of O. nemorosus, second larval instar.
Fig. 116. — Siphon, pecten-teeth, and comb- scale of 0. nemorosus, first larval instar.
generally two branches in 0. caspius, except in the fourth instar, when it is simple, and in 0. nemorosus it is simple in the second instar, sometimes forked in the third, and generally forked in the fourth larval instar.
The first larval instar has been observed in 0. caspius and 0. nemorosus only, and the shape of the comb-scales affords the best character for separating them. Generally speaking, the same differences separate the comb-scales of the first instar as those of the succeeding instar. Thus, in O. nemorosus the terminal spine is considerably bigger than the lateral bristles ; and in O. caspius the terminal spine, though larger than most of the lateral spines, is hardly larger than its neighbours (figs. 108, 116).
These differences arc expressed in a tabular form in the following
keys : —
Key to thk Larvae of British Species of Ochlerotat, rth
[nstar only.
A. The last one or two teeth separated by wide gaps from each
other and from the rest of the pecten. I. Tufted hair lies more or less in a line with the pecten ; no small second tufted hair dorsal to the pecten ; nor any simple hairs on the dorsal surface of the siphon [&g. [09 ;. 0. II. Large tufted hair lies ventral to the pecten ; a small tufted hair lies dorsal to and about half-way along the pecten ; three or four pairs of long, simple hairs on the dorsal surface of the siphon (fig. 11: . . . . . 8. O. rusticus.
B. Pecten-teeth evenly spaced ^except that sometimes the last
tooth is a little further removed from the penultimate tooth than the penultimate from the anti-penultimate . / I. Antennae paler at the base ; anal gills shorter than the last segment. / a. Comb-scales blunt, ending in several sub-equal bristles :
pecten not half as long as the siphon tig. 121) . . 6. O. detritus.
. Comb-scales sharp, ending in one or two teeth somewhat larger than the rest (or sometimes in one decidedly larger than the rest : pecten generally half as long as the siphon (fig. 105) . . . . 1. O. caspius, and 2
; c. Comb scales sharp, ending in one spine conspicuou>l\ larger than the rest ; pecten not half as long as the -.iphon. <i. Pecten teeth stouter with more denticles fig. no)1 4. O. waterhou I2. Pecten-tceth more slender with fewer denticles (fig. 1 1 1 5. 0.autittliA II. Antennae uniformly pigmented : anal gills very large and tapering, usually longer than the last segment ; comb- scales ending in a terminal spine so large that the otL appear as mere hairs or bristles fringing the base of the terminal spine (fig. n . . . . .7.
Key id the Larvae of Brim>h Species 01 Ochlerotatits, includii
ALL THE INSTAR HITHERTO OBSERVED.
A. Fin of the ninth abdominal segment present : more than six- teeth in pecten ; main denticle of pecten-tooth so much larger than the rest that it forms the main part of the tooth : tufted hair with from two to six branches ; no egg-break tooth on the dorsal surface of the head ; mid pair of ] . antennal hairs lying nearly directly anterior to the inner pair.
Second, third, and fourth instar 1 I. No small second tufted hair on siphon dorsal to pecten, nor pairs of simple hairs on the dorsal surface ot the ^Mihon.
1 See footnote on p. 63.
66
a.
b.
6. O. detritus.
The last one 01 two pecten-teeth separated by wide yaps
from each other and from the rest of the pecten (rig. 109) 3. O. vexans.
Pecten-teeth evenly spaced (except that sometimes the last
tooth is a little further removed from the penultimate
than the penultimate from the ante-penultimate).
1. Scales of comb blunt, ending in several sub-equal
bristles ......•••
a. Pecten-teeth 1H-30; four to nine branches in tufted hair ; outer post-antennal hair with more than four branches; inner with two branches ; antennae con- spicuously paler at the base (fig. 121) O. detritus, fourth larval instar. S. Pecten-teeth 10-14 ; two to three branches in tufted hair ; outer post-antennal hair with three to four branches : other antennal hairs single ; antennae uniformly pigmented (fig. 122) . . O. detritus^ third larval instar.
I 2. Scales of comb pointed, ending in one or two spines slightly larger, or one spine conspicuously larger than the other spines or bristles. / a. Terminal spine or spines of comb-scales, though slightly or conspicuously larger than the fringing spines, not so much larger that these appear as mere : bristles, but rather as smaller spines of similar nature.
\ / i. Tufted hair generally decidedly beyond the middle of pecten. Comparatively few denticles on pecten-
O. curi iei.
of pecten. Comparatively few denticles on pecten- teeth . . . . .1.0. Crispins and
a. Pecten-teeth 19-26; five to six branches in tufted
hair : outer post-antennal hair with about eight branches, the others generally simple ; antennae conspicuously paler at the base (fig. 105)
O. caspius, fourth larval instar.
b. Pecten-teeth 14-17 ; four to five branches in tufted
hair: outer post-antennal hair with about five branches, the mid generally simple and the inner generally with two branches : antennae hardly paler at the base (fig. 106) . . O. Crispins, third larval instar.
c. Pecten-teeth 9-13 ; three to four branches in tufted
hair ; outer post-antennal hair with two branches, the mid-hair simple and the inner generally with two branches ; antennae uni- formly pigmented (fig. 107) . O. Crispins, second larval instar.
ii. Tufted hair at about the middle of the pecten ; antennae hardly paler at the base. a. Pecten-teeth stouter and more numerous, with Mime minute denticles at the base, and others often between the larger denticles (fig. no) ' 4. 0. waterhousei.
1 b. Pecten-teeth more slender and fewer, without minute denticles occurring between the larger denticles (fig. in)
5. O. an nn !i pes.
See footnote on p. 63.
i. Terminal spine of comb- than
the others that these appear as mere li lirs or lit:-' fringing the base of the terminal spine; anteni uniformly pigmented; anal gills than the
lasl th of pecten with the last denticle
nspicuously the largest .... i. Pecten-teeth iS-26; four to six branches in tin hair: outer postrantennal hair with t branches, the others generally bifid ; coml generally arranged in about four irregular i of seven or eight fig. 113 . O. nemon , fourth larval ii
ii. Pecten-teeth 12-16; three to five branches in tufted hair: outer post-antennal hair with ti branches, the others simple or sometimes the inner hair is bifid; comb-scale* generally arranged in three irregular rows of about eight each fig. 114
O.nemorosus, third larval insl iii. Pecten-teeth 12-14: two to three branches in tufted hair ; outer post-antennal hair with two brand the others simple; comb- generally
arranged in two irregular rows of seven each
115) . . . . r/«, second larval ins
II. A second small tufted hair lyingdorsal to and about half-way along the pecten ; three or four pairs of long simple hair- on the dorsal surface of the siphon : the main tufted hair lies ventral to the pecten ; the last one or two teeth of the pecten are widely separated from each other and from the rest of the pecten rig. 112 . B. Km of ninth abdominal segment absent : six teeth in pecten : main denticle of pecten-teeth no: so 1 onspicuously larger than the rest that it forms the main part of the tooth : tutted hair of third and fourth instar, simple in first instar : an < breaking tooth on the dorsal surface of the head ; all post- antennal hair* approximately in a curved line. First larval inst.i>
O. nemorosns, and probably the other I'>riti>h I. Scales of comb with terminal spine hardly larger than it*
neighbours (tig. 10- . . . O. caspius, first larval i:
1 1. Scales of comb with terminal spine considerably larger than
the fringing spines (fig. 11 . . U. nan larval ii
V
8. O. ru
<-. Finlaya.
The larva of Finlaya ^eniculata is known from those of the different species of Ochlerotatus by the antennae- which are snv and have not the scattered appressed spines usual in gnat-larvae (fig. 1041 ; and in all the instar but the first by having the coi scales arranged in a single line. The very large anal gills, too, sausage-shaped instead of tapering as in Ochlerotatus. '1 he larva
1 J
68
F inlay a geniculaia shares with exotic species of this genus the habit of living in tree-holes like Anopheles plumbens and OrtJiopodomyia.
With the reservations already made with regard to the larvae of Ochlerotatus in their different instar, it may be said of F. geniculata that the pecten-teeth in the second, third and fourth larval instar
Fig. 117. — Siphon, pecten-teeth, and comb- scale of F. geniculata, fourth larval instar.
Fig. 118. — Siphon, pecten-teeth, and comb- scale of F. geniculata, third larval instar.
120
Fig. 119. — Siphon, pecten-teeth, and comb- scale of F. geniculata, second larval instar.
Fig. 120. — Siphon, pecten-tooth, and comb- scale of F. geniculata, first larval instar.
have, respectively, eight, twelve and fourteen to eighteen teeth ; the comb seven, twelve and fourteen scales ; the tufted hair, two, four and four or five branches (see figs. 117-119) ; the outer post-antennal hair has two or three branches in the third, and three or four branches in the fourth instar ; and the mid and inner post-antennal hairs are simple, though in the fourth instar the inner pair sometimes has two branches.
69
The first instar may be known by possessing no fin on the segment; about six pecten-teeth ; a simple hair on the siphon
egg-breaking tooth on dorsal surface of head ; and all the i antcnnal hairs forming a single row (fig. 120).
i!^^^^^^
^~*^T
^7
122
FlG. 121. — Siphon, pecten-teeth, and comb- scale of O. detritus, fourth larval instar.
Fig. 122. — Siphon, pecten-teeth, and 0 scale of O. detritus, third larval instar.
I I
Key to Larval Instar ok Finlaya geniculata.
Fin of ninth abdominal segment present ; more than six teeth in pecten ; tufted hair with two to six branches ; no eg breaking tooth on dorsal surface of head : mid pair of post- antennal hairs lying directly anterior to the inner pair.
Second, third and fourth larval ins I. Pecten-teeth 14-18; four to five branches in tufted hair ; outer post-antennal hair with from two to four branche- ; middle and inner simple or with two branches ; about fourteen scales in comb fig. 11 . . F. geniculata, fourth larval ii
11. Pecten-teeth about 12; four branches in tufted hair : outer post-antennal hair with two or three branches : middle and inner simple : about twelve scales in comb (fig. 118) ..... F. geniculata, third larval insl
Pecten-teeth about 8; two branches in tufted hair; about seven scales in comb (fig. 119) . /•". geniculata, second larval ii
70
B. Fin of ninth abdominal segment absent ; about six teeth in pecten ; hair on siphon simple ; an egg-breaking tooth on dorsal surface of head ; all post-antennal hairs simple and lying in a single row (fig. 120) . . . F. geniculate/., first larvaL instar.
\?4.
Fig. 123. — Siphon, pecten-tooth, and Fig. 124. — Siphon, pecten-tooth, and
comb-scale of Theobaldia annulata, comb-scale of TlieobalJia annulata,
third larval instar. second larval instar.
Fig. 125. — Siphon, pecten-tooth, and comb-scale of Theobaldia annulata, first larval instar.
FlG. 126. — Siphon, pecten- tooth, and comb-scale of Culex pipiens, third larval instar.
FlG. 127. — Siphon, pecten- tooth, and comb-scale of ( 'ulex pi pims, second larval instar.
FlG. 12S. — Siphon, pecten- tooth, and comb-scale of C 'ulex pipiens, first larval instar.
d. Theobaldia. The four larval instar of Theobaldia annulata differ in much tl
same manner as the instar of the different species of I
namely, in the number of pecten-teeth and comb-scales, and in the
complexity of their post-antennal hairs and tufted hair. The
differences are best tabulated a- follows: —
A. At least inner and outer post antenna! hair compound : tufted hair with from three to eight brandies, and situated near the proximal end of the pecten : comb-scales in more than one row, or irregularly arranged ; pecten-teeth more than seven in number ; no egg-breaking tooth on upper surface of head ; a tin present on ninth abdominal segment.
Second, third, and fourth larval in: I. Outer post-antennal hair with about twelve branches, mid with from one to four branches, and inner with about six brandies ; tufted hair with about eight branches : comb- scales, about sixty in number, in several irregular rows: pecten-teeth about thirty in number, of which about t he- last six are widely-spa< ed and many are hair-like (fig
Theobaldia an nit lata, fourth larval instar. II. Outer post-antennal hair with about live branches, mid post-antennal hair simple, inner with three branches : tufted hair with seven branches : comb-scales, about fifty in number, arranged in several irregular rows : pecten- teeth about seventeen, of which about the last mx are widely-spaced and hair-like (fig. i .
Theobaldia annulata, third larval ins! III. Outer post-antennal hair with about three branches, mid post-antennal hair simple, inner with two branches : tufted hair with about three or four branches ; comb-scales, about twenty in number, in two irregular rows ; n teeth
about fourteen in number, of which about the last thn widely-spaced and hair-like (fig. 124 .
theobaldia annulat B. All the post-antennal hairs simple ; tufted hail
fourth instar is a simple hair in first instar, and situated ventrally to and about half-way down the pecten ; comb- ;les about ten to twelve in a single row ; pecten-teeth six to seven in number, and not hair-like ; an egg-breaking tooth on the upper surface of the head : no tin on the ninth abdominal segment fig. 12; . Theobaldia annulata. first \ 1
e. Culicella. The two species of Culicella can be more readily determim
their larval than by their adult characters. In C tnorsi
the axis of the pecten is mcfrc or less parallel with that of the sipl
7^
and the siphon has no scattered single spines on its surface. In C. fumipennis (fig. 7S), the axis of the pecten lies obliquely with regard to that of the siphon, and there are scattered single spines on the rest of the siphon.
The earlier larval instar have not been observed.
/. Culex. The larva of Culex apicalis has a more slender siphon (fig. 129) than C. pipiens. The species ranks as British only on the strength of an isolated capture. In Culex pipiens (figs. 79, 126-8) there are on the siphon four pairs of tufted hairs (three only in first instar), called so because in the second to fourth instar in other British Culicines they have at least two branches. They are often simple in the earlier instar of Culex pipiens, generally double, and in the last two instar may have three or even four branches. They lie more or less in a line, with the
Fig. 129. — Siphon pecten toolh, and comb-scale of Culex apicalis, fourth larval instar.
pecten, but the first pair (tufted hair 1). lying near the distal end of the pecten, is generally more or less ventral to the pecten ; and the third pair (tufted hair 3) generally lies dorsal to the line of the rest. The following key gives in tabular form the differences between the instar, but it must be borne in mind that the numbers of the pecten-teeth, comb-scales and branches in the hair have a considerable margin of variation, and so those given in the key are only approximate.
A. No tin on ninth segment ; three pairs of simple (not tufted
hairs on siphon : about four teeth in pecten ; comb-scales in a single row of about eight to ten ; all post-antennal hairs simple : an egg-breaking tooth on dorsal surface of head (fig. 128 ....... Culex pipiens, first larval instar.
B. A nn on ninth segment; four pairs of hairs (simple or
tufted on siphon ; more than four teeth in pecten ; comb- scales in at least two rows or irregularly arranged ; post- antennal hairs at least double ; no egg-breaking tooth on dorsal surface of head.
1 1
Comb-scales in two irregular rows of about ten scales in each row ; live to seven teeth in pecten ; all four pail tufted hairs on siphon may have two branches, but numbers three and four may be simple ; outer p< antennal hair with two or three branches, mid and inner with two branches (fig. 127) . . Culex pipiens, second larval instar.
Comb-scales in at least three irregular rows, tending form a triangular patch containing thirty to fifty teeth. ". Ten teeth in pecten ; tufted hairs 1 and 2 generally double, 3 and 4 often double but may be simple : outer post-antenna! hair with from three tosix branches, mid with two or three branches, and inner with three branches ( tig. 126) .... Culer pipiens, third larval in Twelve to fifteen teeth in pecten; tufted hair 1 generally with three branches, 2 with three or even four branches, 3 generally with two branches, and 4 generally with three branches : outer post-antennal hair with from seven to nine branches, mid with three or four branches, and inner with four or five branches (fig. 79).
Culex pipiens, fourth larval instar.
III. -SYSTEMATIC ACCOl'XT. 1.— ANOPHELES, Meigen.1
Anopheles; J. W. Meigen, 1818, Systematische Bcschrcibun^ der bekanr.ten
Europaischen zweiflugeligen Insekten, vol. i, p. 10. ( ienosyntypes, Culex bifurcatus Linnaeus and Anopheles maculipennis
Meigen. Genolectotype, Culex bifurcatus Linnaeus. See D. W. Coquillett, n>io.
Proc. United States National Museum, vol. xxxvii, p. 5 ~
1. Anopheles maculipennis Meigen.5
Plate I., and figs. 7. 10, 12, 15, 18, 27, 40, 44, So, 83, S<<. 89, 92,
98, 1 00, 102.
Anopheles maculipennis, Hoffmgg. ; Meigen, 1818, op. cit., \>. 11. [Note: Meigen's ascription of the name maculipennis tu Hoffmani probably
refers to an MS. label.]
1 For an account of the distribution of Anopheles in Britaii G II. 1 Nut tad I,
L. Cobbett and T. Suangeways-Pigg, 1901, Journal of Hygiene, v.. I. i, pp. 4 4 • W. D. Lang, 1918, A Map showing the known distribution in England and Wales ••(" the Anopheline Mosquitoes, British Museum (Natural History) : and I E.
Annals of Applied Biology, vol. vi, pp. 40 7.
'-' For a full account of the anatomy and life-history of this G. H. F. N'ottall
and A. E. Shipley, 1901-1913, Journal of Hygiene, vol. i, nos. . and 2, \ , ii, no. I, and vol. iii, ii". 2.
74
The spotted wings are generally enough to distinguish A. macnlipennis, not only from the other British species of Anopheles, but from all other British gnats, except Theobaldia annulata • and even if only the rubbed wing is available, the relative positions of the cross-veins, as described above, will distinguish these two forms (fig- 33)- If the wings are rubbed, or if for any other reason there is doubt, the best characters for distinguishing A. maculipennis from A. bifurcatus and A. plumbeus are those of the thoracic scale-tuft (see above, p. 33, figs. 40 -41). The difference between the scutella of A. macnlipennis and A. bifurcatus is too slight to be of much value ; and to compare the breadth of the wing-scales, it is necessary to have already the wings of the two species as standards. In the case of a male, the characters of the genitalia (fig. 44) are absolutely diagnostic.
The larvae of A. maculipennis are most easily recognised, especially when alive, by the dendroid outer anterior clypeal hair (figs. 10, 80, 86, 92). This lies over the brush, and, in the living larva, is seen at once with a hand-lens when the larva even momentarily retracts its brushes.
A. maculipennis appears to be common all over England and Wales wherever breeding conditions are suitable. Its abundance in any district depends, apparently, partly upon the locality itself, but also varies from year to year. Its distribution in Scotland and Ireland has not been worked out at all fully ; but since the species has been found in both countries, it is probably widely distributed where there are the requisite breeding conditions. The favourite breeding-places seem to be the shallow margins of weedy, but not foul, calm, open1 water ; and there is also required a certain degree of warmth. That A. maculipennis does not avoid brackish water is shown by its abundance, observed by Dr. Davidson, in the brackish-water dykes in the neighbourhood of Sandwich, Kent.
The eggs are first produced when the flies emerge from hibernation, in March, in mild seasons, but generally in April. The}- are laid, probably during the night or early morning, and singly, not, as in
1 Mr. F. W. Edwards has observed that, even when found in the same water. ./. maculipennis prefers an open station, while A. bifurcatus prefers a shaded station. His atten- tion was also drawn to the fact by Dr. Penrose of Bournemouth. See also J. Feytaud and E. Gendre, 1919, Bull. Soc. Path. Exot. Paris, vol. xii, pp. 178-182.
Culex, in rafts formed of numbers glued together; though they often take up definite positions of equilibrium with regard to one an and often form regular patterns. Within a few days the larvae hatched, and within a few weeks emerge as flies, having pa rough
their four larval instar as well as the pupal instar. The advent of th< newly-emerged flies in a district is announced by the presence males as well as females; for the hibernating flies are females on During the day-time and in inclement weather the flies prefer to shelter in buildings and similar situations : but i illy in the evenings in calm weather the females fly forth and bite, ;vm\ the males gather in swarming companies. Fresh broods of eggs continue- to be laid throughout the summer, until about the end mber. By the middle of October no more larvae or pupae are found in fr< waters nor male flics in the land. The female flies shelter in buildings, and are especially fond of occupied cowsheds, pigstyes and stables, where they keep comparatively warm, and in the milder spells of winter always have a meal hand)*. In these situations they may be found in immense numbers, and are particularly fond of settling upon cobwebs. A wholesale destruction of these hibernating femali promises to be an effective means of reducing the numbers -/. maculipennis in a district in the following season.
Towards the end of summer the flies are often found with larval water-mites attached to the bodies, wings or legs.1 These mites have been observed to suck and weaken the flies. They ar arativi
rarely found on the larvae : and how they obtain a hold on die fly is not known. Nor is it easy to understand how they return to the water. There is no reason why a male fly should approach water ; and a female weakened and finally dying under the attack of a mite would in the majority of cases collapse far (from the mi: int of
view) from any water. A mite on A. maculipennis captured, by Mr. D.J. Scourfield during August was submitted to Mr I - . who kindly determined it forme and pronounced it to be th : a
species of Arrhenurus. Larval Trombidinm (possibly the same mite under another name) have also been recorded from the fli Anopheles maculipennis and A. bifurcatus. Again, J Curt 4.
British Entomology, explanation of pi. 210) quotes Haliday .1- saying
1 SeeC. Wesenlier^-Lund, 191S, \ iilensk. Mo risk naturh. 1
76
that A. maculipennis ''are very much infested by a small reddish parasite ( Ocypete rubra ? ) ; I have found ten of these attached to the abdomen of a male."
A larva collected by Major A. Macdonald in Kew Gardens was found to be full of the diatom Fragilaria sp., probably F. virescens (kindly determined for me by Mr. F. B. Taylor, of Bournemouth). Occasional diatoms occur in larval mosquitoes, but it is not usual to find them in large numbers ; and, since diatoms must often abound where the larvae of A. maculipennis are feeding, it appears probable that the diatoms in the case described were eaten deliberately.
2. Anopheles bifurcatus (Linnaeus).
Plate II., and figs. 41, 42, 45, 81, 84, S7, 90, 93, 96, 99, 101, 103.
Ciilex bifurcatus ; Linnaeus, 1758, Systema Naturae, Regnum Animale, editio decima, p. 603.
As a general rule, the unspotted wings of A. bifurcatus readily distinguish it from A. maculipennis and the coloration of the thorax from A. plumbeus. But in doubtful cases the characters of the thoracic scale-tuft are the most useful criterion to distinguish A. bifurcatus from A. maculipennis (figs. 40- 1) ; and the shape of the scutellum to distinguish A. bifurcatus from A. plumbeus (figs. 42-3). In the case of a male, the characters of the genitalia are absolutely diagnostic of the three species (figs. 44-46). These points of difference have been described in detail above, as also have the larval characters, the most useful of which are the simpler outer anterior clypeal hairs (seen best in the live larva above the brushes) to distinguish it from A. maculipennis, and the large, branched post-antenna! hairs to distinguish it from A. plumbeus (figs. 81, 87, 93).
A. bifurcatus is as widely distributed as A. maculipennis in England and Wales, and is probably equally common. In a few localities it has been recorded as commoner. But the numbers of A. maculipennis vary considerably from year to year in a given district, while those of A. bifurcatus remain more constant. A. maculipennis, however, is the more noticeable species, owing to its fondness for entering houses and its habit of hibernating as a female fly.
A. bifurcatus hibernates as a larva (probably, as a rule, if not always, in the third instar), which, as soon .is the spring-weather comes, completes its development and emerg a fly. I
quently, male A. bifurcatus arc found earlier in the sea- mi than m; A. maculipennis, which have to undergo their whole life-history from the egg at the beginning of each season, while A. bifurcatus starts a three-quarter grown larva. In 19 1 8, A. bifurcatus appeared early as February.
The habit of hibernating as a larva probably explains the more constarit numbers of A. bifurcatus from year to year. For a few warm days in early spring, followed by cold weather, will tempt forth the hibernating females of A. maculipennis into the open, and they will stand the chance of being overtaken and destroyed by the suddenly returning cold. Whereas the larva in the water remains under for more uniform conditions, and can live in or under ice.
The general habits of the two species are similar. A. bifurcatus, however, prefers the shelter of foliage to buildings, and thi i^
comparatively uncommon in houses and more common in wooded country ; and it will bite more readily by day than A. maculipennis. Adult A. bifurcatus, however, have been observed by Mr. F. W. Edwards resting under the raised floor of a bungalow at Wood Walton Fen, Hunts, preferring cobwebs for their settling places. In one case only was a mosquito observed to have been caught by a spider and shrouded in silk. In the Sandwich district, where it was remarked that A. maculipennis flourished in brack ish water, the evidence shows that A. bifurcatus prefers the fresh, if it does not actually avoid brackish water. In the same district A. bifurcatus has also been found in a wooden vessel in a farmyard — practically a " water-butt," which is a most unusual situation for an Anopheles, and unknown to harbour the genus in town areas. In Palestine during 191S, Major E. E. Austen, D.S.O., - A. bifurcatus breeding in wells and underground cisterns, and mentions it especially as abundant in wells of the 1 rar irdcns
near Jaffa.
Larval mites are found on A. bifurcatus towards the end ol the summer, as they are on A. maculipennis. Remarks on these will be found in the description of the latter sped*
73
3. A. plumbeus Stephens.
Plate III., and figs. 43, 46, 82, 85, 88, 91, 94, 97, 99a, 101a, 103a.
Anopheles plumbeus; J. F. Stephens, 1828. Zoological Journal, vol. hi,
P- 5°3- Anopheles nigripes, n. sp. ; C. Staeger, 1839. Kroyer's Naturhistorisk Tid-
schrift, vol. ii, p. 552.
The small size and dark colouring of A. plumbeus with the ashy-grey longitudinal thoracic markings will generally distinguish it from A. bifurcatus. But, in a case of doubt, the shape of the scutellum (fig. 43) and, in the male, the genitalia (fig 46) afford the best criteria. It is unlikely that A. plumbeus and A. maculipennis will be confused, but the differences described above (pp. 34-5) should obviate all difficulties. The larva of A. plumbeus has a more stumpy look than that of A. maculipennis and A. bifurcatus, and may be most easily distinguished from the larvae of both species by the post- antennal hairs, which are exceedingly small, difficult to see, and simple, instead of pinnately branched. The outer anterior clypeal hairs are simple, or nearly so (figs. 82, 88, 94).
A. plumbeus appears to be widely distributed in England and Wales, and is common in some localities. It also occurs in Scotland and Ireland. On several occasions it has been taken in houses, though essentially a sylvan species; and, as far as is known, confined during its larval and pupal life to water-filled holes in trees.1 The larvae of Finlaya geuiculata are often found sharing these holes with A. plumbeus'} A. plumbeus larvae have been found during the winter (1918) by F. \V. Edwards, and I have kept in captivity from September, 1918, till April, 1919, larvae of A. plumbeus captured during August, 191S, by Angus Macdonald, jun., at Culross, Fifeshire. A curious point with regard to the breeding of A. plumbeus is the apparent scarcity of the larva compared with the frequency of the imago. In more than one district where the fly is common, a search in likely tree-holes has failed to reveal the larva, or no tree-holes have been discovered. Observers report that A. plumbeus bites more viciously
1 Beech-trees as a rule, but it has been taken from Chestnut (24, iii, 1919 ; Botanical Gardens, Cambridge : 1". W. Edwards), and probably occurs in any trees providing suitable holes. See also under OchlerotaUis geniculates. Theobald records A. plumbeus from a peat-cutting.
- Hoth species have also been taken with Orthopodomyia and Stegomyia, see pp. 109-10.
than the other two British Anopheles, and by day as well as by night. It has quite lately been established that A.plumbeus can be inf< I with malaria; see B. Blacklock and II. i\ Carter, [919, Ann. ' Medicine and Parasitology, vol. xiii, p. [87.
II. AEDES, Meigen.
Aedes, Hoffmgg. j J. W. Meigen, 1818, Syst. Beschr. bekannt. Eui :tl.
Insekten, vol. i, p [3. Genotype, Aedes cinereus, Miegen. Meigen's ascription of the name to Hoffmannst e r> to an MS.
by that collector on the material Meigen was describii
1. Aedes cinereus Meigen. Pigs. 5, 11. 13, 14. 17, 29, 75.
? Ctdex ciliaris : Linnaeus, 1 7 ' > 7 - Systema Naturae, editio • ma
reformata, vol. i, part 2, p. 1002. Aides cinereus, Hoffmgg. ; J. W. Meigen, 1 Syst. Beschr. bekannt. Eur
zweifl. Insekten, vol. i, p. 13. [Not' . - above under the genus Ak Aedes ru/us, mini. : 1!. A. Gimmerthal, 1845, Bull. ^,,c- I n 1 j >. Nat. Moscow,
vol. xviii, p. 295. Culex nigrituhis ; J. W. Zetterstedt, 1850, Diptera Scandinaviae. i\.
P- 3459- non Culex nigritulus, Zetterstedt : Y . V. Theobald, 1901, .\ Monograph of I
Culicidae or Mosquitoes, vol. ii, p. 140, which is Culex pipiens, I. inn.
var. doliorum, F. W. Edwards, q.v. Aedes fziscus, h. sp. ] C. R. Osten Sacken, [877, Bull. United States G
and Geogr. Survey, vol. iii, p. 191. ./ .-' . leucopygus, n. sp. ; .\. Eysellj 1903. Abhandlungen und Bericht d
Vereins fur Naturkunde zu Kassel, vol. xlviii. p. 285.
The male 1 if Aedes cinereus may at once be known by its very short palpi. The female at first sight Looks like an obscure Ochlerotatus, since it has the pointed abdomen of that genus. The marked contra however, in the female, between the reddish ground-o >li air < if the th< >ra\ and the almost black head and abdomen, sufficient!) uish it
a glance from the various species of Ochlerotatus, and an examinati under a high-power lens or microscope show- the wid< in the
crown of the head in both sexes. In the male the thorax is bla The larva generally resembles those of the various 5| Ochlerotatus, but is distinguished from these by the com pa slenderness of the siphon and by the position of the ban- tuit decidedly beyond the middle of the siphon (fig. ; -
8o
F. W. Edwards considers the North American A'cdes fuscus to be identical with the European A. cinereus. In America A. fuscus is believed to pass the winter in the egg. We have no records of A'cdes cinereus during the winter, and it may be that it winters as an egg in Britain as it is supposed to do in America.
A. cinereus in Europe has been recorded from Norway, Sweden, Austria, Hungary and Italy (see F. V. Theobald, 1901, Monograph of the Culicidae or Mosquitoes, vol. ii, p. 234, and 1907, vol. iv, p. 539) ; from Germany (Habichts-Wald, W. of Cassel, Hessen, see A. Eysell, 1903, Abh. Ber. Ver. Naturk Kassel, vol. xlviii, p. 285) ; from Holland (see J.-C. H. de Meijere, 191 1, Tidschr. o. Entomologie, vol. liv, p. 148) ; Denmark ; and from Russia (see under A'cdes
rufus).
Though widely distributed, A'cdes cinereus does not appear to be very common in Britain ; or, at least, not often observed. The general situations indicated in the British records suggest that it is mainly a river-haunting species. I have gathered the following records : —
Cambs. — Baitsbite, N.E. of Cambridge, Chippenham, N. of New- market, and Wicken, S. of Ely. See F. IV. Edwards, 19 12, The Entomologist, vol. xlv, p. 260.
Dorset. — Studland. See F. IV. Edwards, under Cambridgeshire records.
Hants. — Bournemouth ; flies and larvae; 10 and 11, vi, 1908 ; colld. H. J. Waddington. British Museum Collection.
Brockenhurst ; flies and larvae; 11 and 26, vi, 1906; colld. C. O. Waterhouse. British Museum Collection.
Herts. — Radwell, near Letchworth. F. W. Ed-wards colld.
Hunts.— Wood Walton Fen, W. of Ramsey ; 13, vi, 191 3 ; colld. Hon. N. C. Rothschild. British Museum Collection.
Middlesex— -Harefield, N. of Uxbridge ; 21, viii, 1916 ; colld. F. W. Edwards. British Museum Collection.
Stanmore ; 10, viii, 1918 ; colld. K. G. Blair. British Museum Collection.
Norfolk. — Ormesby, N. of Great Yarmouth. See F. IV. Edwards, under Ca m bridgeshire records.
Suffolk.— Tuddenham, N.E. of Newmarket ; J. E. Collin. See F. IV. Edwards, under Cambridgeshire records.
Wales.— Crymlyn Bog, S.W. of Neath, Glamorganshire ; 14. vi,
colld. Lt.-Col. Yerbury. British Museum Collection. Scotland. — Edinburgh. See F. IV. Edwards, under Cambridgeshii
records.
III. OCHLEROTATUS, Arribalzaga.
Ochlerotatus, nov. gen. ; 1. I. Arribal/.aga, [891, Dipterologia Argentina. Revista del Museo de La Plata, vol. i, p. 374, and vol. ii, p. 1 j.3. Genosyntypes, Culex albofasciatus Macquart, and Ochlerotatus confirmatus, n. sp. Genolectotype, 0. confirmatus ; see 1). \V. Coquillett, 19 10, Proc. United States National Museum, vol. xxxvii, p. 577.
1. Ochlerotatus caspius (Pallas). Plate IV., and figs. 20, 25, 28, 30, 47, 51, 59, 105 108.
Culex caspius ; P. S. Pallas, 177 1, Reise durch verschiedene Provinzen des
Russichen Reichs, p. 475. Culex punctatus ; J. W. Meigen, 1804. Klassifikazion und Beschreibung der
europaischen Zweifliigligen Insekten, vol. i, p. 6. Culex dorsalis; J. W. Meigen, 1830, Systematische Beschreibui ig
bekannten Europaischen zweifliigeligen Insekten, vol. vi, p. 212. Culex penicillaris N. ; C. Rondani, 1872, Bull. Soc. lint. Ital., vol. iv, p. 31
(fide]. Villeneuve, 1919, Bull. Soc. Ent. France, p. 56). Culex pulchripalpis ; F. V. Theobald, 1901, A Monograph of the Culicidae or
Mosquitoes, vol. ii, p. 16 {non Rondani, 1872, bull. Soc. Ent. Ital.,
anno, iv, p. 31). It is impossible, since the type specimen is not available, to be absolutely
certain that Pallas' Culex caspius is the species generally known as
Ochlerotatus dorsalis ; but the probabilities are so great that there is
justification for reviving this ancient name ; and specimens oi rsalis
from the Caspian are in the British Museum Collection.
The brilliant coloration of the head and thorax, the white bands on the hind tarsi each embracing two tarsal joints, and on the abdomen each embracing two abdominal segments, make 0. caspius one of the most easily recognisable of British mosquitoes. The gr breadth of the light and dark scales of the wings also are characteristic of this species. The larva is to be known from those of other species of Ochlerotatus by the length of the pecten, which is about half as long as the siphon, the tufted hair lying beyond the middle of the siphon.
82
O. caspius appears to be abundant in southern England, and the larva occurs both in inland waters and in brackish water near the sea. In the latter situation it is generally found in company with O. detritus. The larvae are found in spring and early summer, and the flies soon appear. In mid-summer neither flies nor larvae are generally seen, and often the breeding-pools are dried up ; but when rain)- weather fills the pools again, both larvae and flies quickly re- appear, and the flies are often noticed in great abundance at the end of summer and in early autumn. It is not known in what stage O. caspius spends the winter. Flies of this species are often found far from any likely breeding-haunts ; for instance, one was taken in my garden in Chelsea in August, 1918, at least half-a-mile from any water such as a pond, and nearly a mile from any pond likely to afford a suitable breeding-place. Mr. F. W. Edwards tells me that O. caspius has been observed biting indoors. It is seldom that any species of Ochierotatus enters houses.
H. Dyar, L. Howard and F. Knab (1917, The Mosquitoes of North and South America and the West Indies, vol. iv, p. 634.), in discussing the possible identity of two American species, Q. onondagensis (Felt) and O. curriei (Coquillett) with O. caspius (as O. dorsalis), suggest that the sea-side specimens of O. caspius are of a different species from those that breed inland in fresh waters, and that an examination of larvae from salt and fresh waters respectively will reveal differences comparable with those of the larval O. onondagensis and O. curriei in America.1 Specimens of larval O. caspius (probably third instar) from brackish water of Millbrook Common, Southampton, and specimens of the third larval instar from Mitcham Common, Surrey, have been compared by Mr. F. W. Edwards, and some of those from Mitcham Common have comb-scales resembling the Millbrook Common specimens, while others have the terminal spine considerably larger. It is possible that two forms are confused.
O. caspius has been recorded from Scandinavia, Holland, Germany (Berlin), and Austria (see F. V. Theobald, 1901, Monograph of Culicidae or Musquitoes, vol. ii, p. 18) ; also Southern Russia (Pallas, 1771, loc cit.) ; it also occurs in Macedonia, whence Major R. A. P.
1 Dyar and Knab now regard these species as one (191 7, Insec. Inscit. Menstruus, vol. v, p. 122).
■
Hill, R.A.M.G., has sent me specimens, and see J. Waterston, [918, Bull. Ent. Research, vol. ix, p. 7 ; Palestine; Mesopotamia, and in Northern Africa (see F. \Y. Edwards, 191 1, Bull. Ent. Research
vol. ii, p. 249) ; also France and Italy.
I have gathered the following British records : —
Essex. — Beckton Marshes, London, E. ; iv, 1919 ; colld. F. \Y. Edwards see F. W. Edwards, 1917, Bull. Ent. Research, vol. vii, p. 217. British Museum Collection.
Royal Albert Dock; colld. Dr. Rees. See F. /'. Theobald 1901, A Monograph of the Culicidae or Mosquit .'. ii, p.
(recorded as Culex pulchripalpis Rondani, and it is suggested that the}- were introduced on some ships coming from Italian port-- — see, however, p. 112 1. Hants. — Millbrook Common, N.W. of Southampton ; larvae, 13, ix, 191S, and flies, 13, viii. 1918; colld. Corporal Ryan. R.A.M.C. Received per dipt. M. Gross, R.A.M.C. Kent. — Charlton. See F. IV. Edwards, 191 2, The Entojnologist, vol. xlv,p. 195.
Dartford Marshes ; 29, v, 1902 ; colld. F. W. Edwards. British Museum Collection.
Lewisham ; 27, viii, 1899 ; colld. R. S. Pengelly. British Museu m Colh 'ctit >//.
Rochester. See F. IV. Fdwards, 1912, The Entomologist, -col. xlv, p. 195. Middlesex. — Chelsea; In garden; Trafalgar Square; 12, viii, 1918 Colld. IV. D. Lang.
Chiswick ; 3. ix. 191 1 ; colld. F. W. Edwards. British Museum Collection.
Stamford Hill, London. N. ; 30, viii, 1899; colld. A. Milton. British Museum Collection. Suffolk. — Aldburgh ; 14 and [9, viii, [895 ; colld. A. Piffard ; s Entomologists' Monthly Magazine, 1895, series 2. vol. vi, p. 227. British Museum Collection. Surrey. — Battersea Park ; 30, vii. [918. Colld. Mrs. W. D. Lan
Camberwell ; ix, 1918 ; colld. Dr. Simpson. British Mus
Collection.
2
§4
Mitcham Common ; larvae colld. Miss L. E. Cheesman, 26, vii, 191S ; pupated 28 and 29, vii, 1918 ; emerged 1, viii, 1918 ; another emerged (presumably pupating later), 14, viii, 191 8. British Museum Collection.
Putney; ix, 19 17. Colld. G.J. Arrow.
Worcestershire. — Forest of Wyre. See B. W. Edwards, 191 2, The Entomologist, vol. xh\ p. 195.
Wales. — Tal-y-bont, N. of Barmouth, Merionethshire ; reared from larvae; vii, 1914 ; colld. F.W.Edwards, 1917 ; see Bull. Ent. Research, vol. vii, p. 217. British Museum Collection.
2. Ochlerotatus curriei (Coquillett).
Culex Curriei, new species ; D. W. Coquillett, 1901, Canadian Entomologist, vol. xxxiii, p. 259.
Ochlerotatus curriei closely resembles. 0. caspius, but the brown coloration of the thorax is not nearly so bright, and the whitish markings form a pair of broad bands instead of taking the form of narrow lines. The wing scales, too, are narrower than those of 0. caspius, and the light and dark scales are more segregated along separate veins or parts of veins, than uniformly mixed as in O. caspius ; thus, longitudinal veins 3 and 5, and the forks of longitudinal vein 4, have dark scales for the most part in 0. curriei. No British specimens of the larva have been found ; but it closely resembles the larva of O. caspius — indeed, no difference between the larvae of these species is discernable from the evidence of the published figures of O. curriei.
This species has been added to the British fauna only since last September, when Dr. Hugh Scott took it in numbers in swampy hollows on the heaths S.E. of Wareham, Dorset. On the 15th Sept., 1919, it occurred on Stoborough Heath, " in numbers, biting fiercely, at about 4.30p.m. (summer time) on a cool, dull, hazy afternoon"; and on 23rd Sept., Middlebere Heath, "biting, between 12 and 3 p.m. (summer time), in spite of high, rather cold wind, and clouds alter- nating with hot sunshine." Dr. Scott also noted that none occurred
near the coast north of Studland, between Littlesea Merc and the Specimens are in the Cambridge University Museum and in the British Museum. It also occurs in Denmark. Sweden and X. .V
3. Ochlerotatus vexans (Mcigeni. Figs. 48, 52, 60, 109.
Culex vexans; J. W. Meigen, 1830, Systematische Beschreibung der bekann-
ten Europaischen zweifliigeligen Insekten, vol. vi, p. 241. Culex sy/vestris, n. sp. ; F. V. Theobald, 1901, A Monograph of the British
Culicidae or Mosquitoes, vol. i, p. 406, pi. xx.w, fig. <
Ochlerotatus vexans is known by the very narrow white bands at the basal ends of the hind tarsal joints (fig. 48) ; otherwise it resembles O. waterhousei and O. annulipes, but has only dark scales on the wings, and the posterior border of the pale abdominal bands is undulating (fig. 52) ; the male genitalia, too. are very distinctive ( fig. 60). I have not seen a larva, but it has been described and figured by H. Dyar, L. Howard, and F. Knab (Mosquitoes of North and Central America and the West Indies, 1917, vol. iv, p. 695, and [912, vol. ii. pi. lxvi) as Aides sylvestris, and may be known from other British species of Ochlerotatus, except O. rusticus, by the two distal-most teeth of the pecten being widely spaced ; and from O. rustic/is by the tufted hair, which is in a line with the pecten (fig. 109).
0. vexans occurs in Scandinavia, Russia, Austria, Germany anil Holland (see F. V. Theobald, 1901, A Monograph of the Culicidae or Mosquitoes, vol. i, p. 405), China, Japan, India, Ceylon, Philippines, Borneo, and perhaps Fiji (see F. \Y. Edwards, i-ii;. Hull. Ent. Research, vol. vii, pp. 218-9), an^ (described as Aides sylvestris) in North America, where it is referred to as a woodland species. It is, apparently, rare in Britain ; but F. YV. Edwards I Entomologist, 1 vol. xlv, p. 195) records it from Mildenhall, Suffolk, colld. C. <i. Lamb, vii, [894 ; and since then he tells me he has seen specimens from Shotover, near Oxford (colld. A II. llamm. 5, viii. [918, two males), and from Coe Fen, Cambridge (colld. F. Jenkinson, one female
There are, in the British Museum Collection, some specimens from the Clifton Collection, which, though without information ility,
are probably British.
86
t
4. Ochlerotatus waterhousei (Theobald).
Figs. 49. 53, 61, no.
Culex Waterhousei, sp. n. : F. V. Theobald, in C. O. Waterhouse, 1905, Annals and Magazine of Nat. Hist., series 7, vol. xvi, p. 674.
Ochlerotatus waterhousei and O. annulipes are very much alike, and the differences given in the tables above (pp. 40,42-3), and in figs. 49-50, 61-2, must be referred to for distinguishing them. The larva of O. waterhousei may be distinguished from that of O. caspius by the length of the pecten ; from O. rusticus by the position of the tufted hair ; from O. vexans by the spacing of the last two teeth of the pecten ; from O. detritus by the number of teeth in the pecten ; from O. nemorosus by the length of the anal gills ; and from O. annulipes by the length of the pecten-teeth (fig. 1 10 ; see, however, footnote on p. 63).
O. waterhousei has been so confused with O. annulipes (see under that species) that it is not possible to determine its range with certainty. Probably it is not so common in continental Europe as 0. annulipes (which is the common form in France, see J. Villeneuve, 1919, Bull. Soc. Ent. France, p. 56, as Culex cantans). In England, F. W. Edwards (191 2, The Entomologist, vol. xlv, p. 218, as Ochlerotatus inaculatus) refers to it as widely distributed and probably common. The larvae are found in early summer (in shadiest pools in thick woods — F. W. Edwards) ; and the fly generally towards midsummer. It is not known in what stage the winter is spent. The following are some records of its occurrence : —
Bucks. — Burnham Beeches ; 7, v, 19 12, colld. F. W. Edwards ; 10 and 28, vi, 1907, 18, vi, 1908 (larvae and pupae) ; colLd. C. O. Water- house. British Museum Collection.
Essex. — Epping Forest; larva colld. Miss L. E. Cheesman, v, 191 8 ; pupated 15, v, emerged 19, v; fly colld. H. Main; v, 1918 ; see p. no.
Hants. — Brockenhurst ; 5 and 16, v, 1904; 5 and 7, v, 1905 ; pupae and flies ; colld. C. O. Waterhouse. British Museum Collection.
Herts. — Bushey Heath ; 27, vii, 191 2 ; colld. F. W. Edwards. British Museum Collection.
Felden, S. of Boxmoor ; 7, v, 1899 ; colld. A. Piffard. British Museum Collection.
Knebworth; iv, 1919 ; larvae; colkl. F. W. Edwards, British
Museum Collection.
Hunts. — Wood Walton Fen, W. of Ramsey ; 15 15. iv, [914; colld.
F. W. Edwards. British Museum Collection.
Kent. — Hever, W. of Tonbridge ; 8, vii, 1907 ; colkl. Lt.-Col. Yerbury.
British Museum ( 'ol lection.
Middlesex. — Novver Hill, Tinner ; i, v. [914; colld. V. \V. i. irards.
British Museum Collection. Norfolk. — Merton, S. of Walton ; 31, v, 1908 and io, vi, 1900; colld.
Lord Walsingham. British Museum Collection. Shropshire. — Longner Hall, S.E. Shrewsbury ; in garden ; v. 1
vi, 1908 and 12, x, 1912 ; colld. R. F. Burton. British Museum
Collection. Suffolk. — Barton Mills ; v, 1916 ; colkl. F. W. Edwards. British
Museum Col lectio?/. Sussex. — Angmering Ponds, S.F. of Arundel; I and 27, vii, [9 7;
colld. Rev. A. E. Eaton. British Museum Collection.
Fridge, S. of Tunbridge Wells, Kent; 11. vi, [886; colkl.
G. H. Verrall. British Museum Collection. Goring Woods, X.W. of Worthing ; 20, 24 an
colld. Rev. A. E. Faton. British Museum Collection. Scotland. — Dingwall, Ross; 29, v, 191 1; colkl. Lt.-Col. Yerbury. British Museum Collection.
5. Ochlerotatus annulipes (Meigen). Figs. 50, 54, 62, 111.
Cutex annulipes; J. W. Meigen, 1830, Systematische beschreibung der
bekannten Europaischen zweirkigeligen Insektcn, vol. vi, p. 241. ? Culex variegatus ; F. de P. Schrank. [781, Enumeratio Insectorum Austriae
indigenorum, p. 482. ICulex maculatus ; J. W. Meigen, 1S04, Klassifika/.ion und Beschreibung
europaischen Xweiflugligen [nsekten, vol. i, p. 4. ? Culex cantans, Hoffmgg. ; J. W. Meigen, 1818, Syst( matische Beschreibung
der bekannten Europaischen /weiilugeligen [nsekten, vol. i. p. <>.
Meigen, in ascribing this species to Hofftnannsegg, is probably only
quoting an MS. label of that collector's writing.]
88
Mr. F. W. Edwards has kindly pointed out to me that Meigen's description of Culex cantans agrees far more closely with his later description of Culex amuilipes than with Ochlerotatus waterhousei, the species generally hitherto considered as identical with Meigen's Culex cantans. Probably, then, Culex annulipes and Culex cantans are the same species. Now, Meigen states that his Culex maculatus is identical with his C. cantans ; in fact, is only the male of that species (1830, loc. cit.) ; but since, the name maculatus has the priority over cantans, this species must be known as OcJilcrotatus maculatus, Meigen, with the synonymy given above ; and the species which has generally been called Ochlerotatus maculatus must be called 0. waterhousei, Theobald. But, until the identity of Culex annulipes with C. cantans is proved, it is best to retain the former name and drop C. maculatus. O. annulipes is unlikely to be mistaken for any other species except 0. waterhousei, which it so closely resembles, that the differences described on pp. 40, 42-3 must be looked for. The larvae, too, are so similar to those of 0. waterhousei, that a satisfactory difference has yet to be found. Note, too, the relative situations in which the larvae are found ; those of 0. waterliousei in the shadiest pools of thick woods, and those of 0. annulipes in open pools. 0. annulipes is probably common on the European continent ; in England it appears to be local. Specimens have been found in the following places :—
Hunts. — Wood Walton Fen, W. of Ramsey. 29, v, 191 3 ; colld. Hon. X. C. Rothschild; and 13-15, iv, 1914, and 17, iv, 1919, larvae, pupae and flies ; colld. . F. W. Edwards ; the larvae were taken from " clear pools under birch and sallow trees " and " clear puddles among reeds" (see F. W. Edwards, 1917, Bull. Ent. Research, vol. vii, p. 215). British Museum Collection.
Norfolk.— Rollesby, N. of Great Yarmouth ; colld. G. H. Verrall. See F. W. Edwards, 1912, The Entomologist, vol. xlv, p. 217.
Shropshire. — Longner Hall, S.E. of Shrewsbury ; one specimen ; vi, 1 91 8 ; colld. R F. Burton. British Museum Collection.
Sussex. — Angmering Ponds, S.E. of Arundel ; 1 and 27, vii, 1907 ; colld. Rev. A. E. Eaton. British Museum Collection.
Rotherfield, S. of Tunbridge Wells, Kent; 6, vi, 1886; colld. G. H. Verrall. British Museum Collection.
6. Ochlerotatus detritus 1 1 laliday)
FiSs- 55. 63, 67, i2i, 1
Culex detritus ; A. H. Haliday, 1833, Entomological Magazine, vol. i, p. 151. Culex sahnus, sp. n. ; E. Ficalbi, 1896, Bull. Soc. Entomologica Italia:
anno xxviii, p. 29. Culex Tcmci, n. sp. ; F. V. Theobald, 1903, A Monograph of the (
or Mosquitoes, vol. iii, p. 193.
Ochlerotatus detritus is distinguished by the white scales that freely scattered over its wings, abdomen and proximal parts of the
legs ; otherwise, it has a blackish ground-colour with pale basal abdominal rings. The light-and-dark speckled wings distinguish it from O. nemorosus, which it otherwise closely resembles and wh< wings are nearly entirely dark-scaled (figs. 67-8) ; the speckling of light scales on the darker parts of the abdomen above and the rows of black spots beneath1 also distinguish it from 0. nemorosus (fi| and the male genitalia of the two species are very different in detail (figs. 63-4). The larva is remarkable among the species of Ochlerotatus for the shortness of its siphon and the numerous small denticles on the proximal part of the pectcn-teeth (figs. 12 1-2). Other details are mentioned in the former section.
O. detritus occurs in Italy (see reference above), and there are in the British Museum Collection specimens from Majorca and Algeria. It is abundant in brackish water in the South of England, and h been taken in Wales and Ireland ; and 0. caspius is nearly al 1 found in company with it ; on the other hand, it does not accompany O. caspius where that species is found breeding inland. It ibable
that 0. detritus winters as a larva or an egg, since larvae are found early in the year, and after that the flies. "The species is, at lea double-brooded, for larvae and emerging flies have been taken in September. Probably, as with O. nemorosus, in summer droughts the shallow waters where they breed dry up, and the impregnated t flies tide over the dry period among vegetation. In Maw 1918, at Great Wakering, Essex, an interesting obs >n was made by
1 The "ventre trifariam fusco-puncl H I
sea-side habitat make it possible to identify certain II
go
Mr. A. J. Grove, who found males of this species swarming in company with males of Anopheles bifurcatus.
The following are British records of OcJderotatus detritus : —
Cornwall. — Sheviock, S. of St. Germans ; 7, ix, 191 2 ; colld. Lt.-Col. Yerbury. British Museum Collection.
Devon. — Tor Point, S. Devon; 19, iv, 1889; colld. Lt.-Col. Yerbury. British Museum Collection.
Essex. — Beckton Marsh, near Royal Albert Dock ; 16, iv, 1914 ; colld. F. W. Edwards. British Museum Collection.
Great Wakering, S.E. of Rochford ; v, 191 8 ; males swarming with males of A noplieles bifurcatus. Colld. A . J. Grove.
Walton-on-Naze ; 4 and 5, v, 1907 ; colld. Lt.-Col. Yerbury. British Museum Collection.
Hants. — Millbrook Marsh, N.W. of Southampton ; larvae and flies ; 8 and 13, viii, 1918, and 13, ix, 1918 ; colld. Corporal Ryan. Per Capt. M. Gross, R.A.M.C
Kent. — Dartford ; 14, vi, 1912 ; colld. Lt.-Col. Yerbury ; also the type- locality of Culex terriei (a synonym of Ochlerotatus detritus), see F. V. Theobald, 1903, A Monograph of the Culicidae or Mos- quitoes, vol. iii, p. 194. British Museum Collection.
Sheerness district; larvae ; 22, iii, 191 8, and 2, iv, 1918 ; and flies, 8, v, 1918. Colld. Major A. Macdouald, R.A.M.C
Sussex. — Worthing; 16 and 26, v, 1907, and 8, vi, 1907 ; colld. Rev.
A. E. Eaton. British Museum Collection. Wales. — Tal-y-bont, N. of Barmouth, Merionethshire ; larvae (in puddle behind shingle bank) and flies; vii, 1914 ; colld. F. W. Edwards. British Museum Collection.
Scotland. — Arrochar, Dumbarton; ix, 191 5 ; larvae in brackish water pools, full of decayed seaweed, reached on occasions by the tide ; colld. Miss L. H. Huie. British Museum Collection.
Brodrick, Arran ; v, 1919 ; brackish pools. Colld. F. IV. Edivards.
h -eland.— Holywood, Co. Down, N.E. of Belfast ; colld. A. H. Haliday. See original description.
Sutton, near Dublin. Per Dr. R. F. Scharjf.
7. Ochlerotatiis nemorosus (Meigen). Plate V., and figs. 9, 56, 64, OS, [13 1
Culex nemorosus; J. W. .Meigen, 1818, Systematische B
bekannten Europiiischen zweifliigeligen tnsekten, vol. i, p. \.
Culex sylvaticus ; J. W. .\reigen, 18 18, op. cit. p. 6 (non Cul 'tic us ;
J. F. Stephens, 1825, Zool. Journ., vol. i, p. 454, which is Culex pip\ see F. W. Edwards, 1912, The Entomologist, vol. xlv. \>. j;
Culex domesticus (parti m) ; J. F. Stephens, 1825, Zoological Journal, vol. i, p. 455; from Hertford {non Culex domestieus : E. Germar, 181 " nach Ualmatien und in das Gebeit von Ragusa, p. 290). The specimens so named in Stephen's collection in the British Museum an -sens,
and one C. nemorosus.
? Culex concinnus ; J. F. Stephens, 1846, Illustrations of British Entomok'- Supplement, p. 19, pi. xliii, fig. 1. (See F. W. Edwards, [912, The Entomologist, vol. xlv, p. 277.)
? Culex fusculus ; J. W. Zetterstedt, 1S50, Diptera Scandinaviae, vol. i\, P- 3459-
? Culex nigripes, Zetterstedt, var. sylvae ; F. V. Theobald, A
Monograph of the Culicidae or Mosquitoes, vol. ii, p 9^6. Culex concinnus of Stephens is either a variety of Ochlerotaius nemOTi (Meigen) or, probably, a distinct species. The general ground-colour of the type-specimen is darker, the dorsal surface of the thorax isgi I the sides, the colour of the abdominal rings is paler, and it is of a smaller size than O. nemorosus. Culex nigripes var. sylvae of Theoba closely with Culex concinnus.
Ochlerotatus nemorosus resembles O. detritus, but has few, if any, pale scales on the wings and on the darker parts of the abdomen above, and the abdomen is not spotted beneath. The pale transvei bands on the abdomen are whitish rather than yellowish, and do not tend to spread medianly to form a longitudinal band in the mid-line. as in O. rusticus. The male genitalia also are very peculiar (see fig. 64). The larva is remarkable for the great size of the anal gills, which taper to a fine point and are not sausage-shaped, as in Fin/aj gem'cu/ata,wh.ich also has very large anal gills ; their size, h< '\\ ever, var:
Hermaphrodite specimens have been described by Edwar 17.
Hull. Ent. Research, vol. vii. p. 2 1 6), taken on Harrow V. Common, and first noticed by him because apparently he w bitten by a male.
92
Ochlerotatus nemorosus is a more or less sylvan species, frequenting" the neighbourhood of woods and copses, and biting freely by day. It is found throughout central Europe. The Algerian record (F. W. Edwards, 191 1, Bull. Ent. Res., vol. ii, p. 248) is O. detritus. It is common in Britain. The larvae appear to occur especially in shallow pools on commons and heaths near woody places, where the bottom is composed of rotting leaves. In such waters they are found in spring, having hibernated in this stage ; and, since these pools readily dry up, the larvae are not met with in fine summers, and do not appear again until the rainy weather at the end of summer or in the early autumn. Then the pools are quickly re-stocked with larvae. But if, as in 191 8, the dried-up pools are re-filled at mid-summer, a brood of larvae are soon produced (see evidence of records in 191 8 and Edward's observations, 1917, Bull. Ent. Research, vol. vii, p. 216). It is almost certain that the impregnated females tide over the droughts among the herbage in woods.
Some British records are as follows : —
Bucks. — Burnham Beeches ; 7, v, 191 2 ; colld. F. W. Edwards. British Museum Collection.
Farnham Common, near Burnham Beeches ; 7, v, 191 2 ; colld. F. W. Edwards. British Museum Collection. Dorset. — Littlesea, Studland ; 31, vii, 191 1 ; colld. Rev. A. E. Eaton ; S, 12, 1.8, and 21, v, 1907, and 2, vi, 1912 ; colld. Lt. -Col. Yerbury. British Museum Collection.
Rempstone Heath, W. of Studland ; 30, v, 1907 ; colld. Lt.-Col. Yerbury. British Museum Collection. Essex. — Coopersale Common, N.E. of Epping ; larvae; 6, viii, 1918. Colld. D. J. Scourfield.
Epping Forest ; larvae ; emerged, 21 and 22, iv, 191 8 ; another larva pupated, 25, iv, and emerged, 29, iv, 191 8 ; colld. Lt. Tickner Edwardes, R.A.M.C. ; also 4 and 6, v, 191 8. Colld. K. G. Blair ; also 30, vii, 19 19. Colld. F. W. Edivards.
Epping Forest, Chigwell Row Recreation Ground ; larvae ; 1 viii, 1 91 8. Colld. D.J. Scourfield. .
Epping Forest, Monk Wood ; 31, iii, 1918. Colld. A. Bacot. Loughton ; larvae from sheltered pool, full and teeming with
larvae of 0. nemorosiis at beginning of May, then dried up, and again teeming at end of July when again filled Colld. Miss L. E. Cheesman.
Hants. — Southampton ; larvae and Hies ; received 2. v, i Id.
Major A. C. Parsons, R.A.M.C.
Lyndhurst ; colld. Lt.-Col. Yerbury. British Museum Collection.
Middlesex. — Hampstead Heath ; larvae, in company with larvae of Culex pipiens, in temporary pool under trees, with leaves at bottom ; 28, vii, 191 8. Colld. K. G. Blair.
Harrow Weald Common; 21, iv, 1912 (see F. \V. Edwan 1917, Bull. Ent. Research, vol. vii, p. 216); colld. F. \Y. Edwards. British Museum Collection.
Stanmore ; larvae; 20, iv, 1918. Colld. K. G. Blair. Stanmore Common ; 18, v, 1916 ; colld. F. W. Fduards. British Museum Collection.
Shropshire. — Longner Hall, S.E. of Shrewsbury; 1, v, [912, and v, 1918 ; colld. R. F. Burton. British Museum Collection.
Surrey. — Oxshott ; 28, v, 1902 ; colld. C. O. Waterhou<e. British Museum Col lee t ion.
Putney; 16, v. 1906; fly and larva; colld. C. O. Waterhous British Museum Collection.
Sheen Common; larvae in a pool recently rilled after being dry since the spring, when larvae of this species were present in it ; 21, vii, 1918. Colld. R. //. Thomas.
Scotland. — Nethy Bridge, S.W. of Grantown, Aberdeen-hire ; colld. Nuttall. British Museum Col lee t ion.
North Sutor, Cromarty ; 12, vi, 1894 ; colld. O. Grant. Museum Collection.
The Mound, N.W.of Dornoch, Sutherland ; 4, viii. [900 ; colld. Lt.-Col. Yerbury. British Museum Collection.
Pitlochry ; Perthshire; 4, ix, [91 5 ; colld. P. A. Buxl Cambridge University Museum Collection.
Torphins, Aberdeenshire, \\" "f Aberdeen and N 1 : >yne colld. J. M. Wright, P.M. British Museum <
94
8. Ocklerotatus rusticus (Rossi). Figs. 57, 65, 112.
Culex rusticus ; P. Rossi, 1790, Fauna Etrusca, vol. ii, p. 333.
Culex ornatus (partim) ; J. F. Stephens, 1825, Zoological Journal, vol. i, p. 454. (non Culex ornatus, Hoffmgg. ; J. W. Meigen, 1818, Systema- tise-he Beschreibung der bekannten Europaischen zweifliigeligen Insekten, p. 5. See F. W. Edwards, 1912, The Entomologist, vol. xlv, p. 277.)
Culex pungenst R.D. ; J. B. Robineau-Desvoidy, 1827, Mem. Soc. Hist. Nat., Paris, vol. iii, p. 407.
Culex quadratimaculatus, Nob. ; M. Macquart, 1834, Histoire Naturelle des Insectes ; Dipteres, vol. i, p. 34.
Culex diversus, n. sp. ; F. V. Theobald, 1901, Monograph of the Culicidae or Mosquitoes, vol. ii, p. 73, pi. xxvii, fig. 107.
Culex nemorosus, Meigen, var. luteovittata, mihi. ; F. V. Theobald, 1901. torn. cit., p. 85.
Ocklerotatus rusticus, though generally resembling O. nemorosus, is really a very distinct species. The yellow colour of the pale abdominal markings, and their tendency to spread medianly so as to form a line down the middle of the abdomen (fig. 57), readily distinguishes 0. rusticus from O. nemorosus. But the male genitalia of O. rusticus (fig. 65) differ so much from,those of the other British species of Ochlerotahis, that they may often be distinguished by the naked eye, mainly owing to their dense hairiness. The siphon of the larval 0. rusticus differs from that of its British congeners in the position of the tufted hair, in the possession of a minute second tufted hair, and in having several single hairs scattered over its dorsal surface (fig. 112). It also shares with O. vexans the peculiarity of the widely- spaced last two pecten-teeth. 0. rusticus does not appear to be a well-known species. It was originally described from Tuscany, and specimens from Ghent are in the British Museum Collection. It occurs in Denmark (C. Wesenberg-Lund) and Macedonia (J. Waterston ). In Britain it seems to be widely-distributed, and replaces O. nemorosus in some districts. The following are some records of O. rusticus from Britain : —
Hants. — Brockenhurst ; 1, v, 1905 (type of Culex nemorosus var. luteovittata); larvae and flies, 26, 27 and 29, iv, 1905 ; fly, 5, v, 1904 ; colld. C. O. Waterhouse. British Museum Collection.
Lyndhurst; 21, v, 1904; colld. G. II. Verrall. British Mm um
Co/lection. Herts— Felden, S. of Boxmoor ; 7, v, 1899 ; colld. A. Piffard. Britx
Museum L ollection. Kent. — Hy 'the ; 13, vi, 1S99 ; colld. A. Piffard. British Museum
Collection.
Sheerness district; iarvae ; 20, iii, 191 S. Colld. Ma;
Macdonald, R.A.M.C
Tunbridge Wells ; 5, vi, 1886; colld. G. H. Verrall. Britx
Museum Collection. Norfolk.- Merton, S. of Walton ; 30, vi, 1907 ; colld. Lord Walsingham
British Museum Collection. Shropshire. — Longner Hall, S.E. of Shrew-bury ; in garden, vi. 190
£ $ , lurking among Scilla nutans, 5, v, 191S ; ? 9, 13. v. [918 ;
colld. R. F. Burton. British Museum Collection. Sussex. — Goring Woods, N.W. of Worthing ; 24 and 2y. \ i.
colld. Rev. A. E. Eaton. British Museum Collection.
Tilgate, Sussex; 23, v, 1897; colld. G. II. Verrall. Brit.
Must 7/ m Collection. Warwickshire. — Brinkk;\v, N.W. of Rugby ; 30, vi, 1902 ; colld. Ma
E. E. Austen, U.S.O. British Museum Collection. Wales. — Porthcawl, S.W. of Bridgend, Glamorganshire; 31, v, 1
colld. Lt.-Col. Yerbury. British Museum Co/lection. Locality not specified. — See G. H. Verrall, 1901, A list of British
Diptera, second edition, p. 13 (as Culex rusticus).
IX. E IN LAY A, Theobald.
Fiulaya, now gen. ; I . X . Theobald, 1903, A Monograph of the Culicidae or Mosquitoes, vol. iii, p. 281. Genosyntypi ilia, n. sp., and
Culex Kochi, Donitz. Genolectotype, Fiulaya ; 1
H. Dyar, L. Howard, and F. Knah, 1 «> 1 7, The Mosquitoes North and South America and the West Indies, vol. iv. p. (>i
1. Fiulaya geniculates (Oh\i< ; Figs. 58, ' ''. 104. 1 17 120.
Culex genicuiatus ; G. A.Olivier. [791, Encyclope'die Me'thodique, Histoire
Naturelle, Insectes, vol. vi, p. 134-
96
Culex lateralis, Meg. : J. W. Meigen, 1818, Systematische Beschreibung der bekannten Europaischen zweifliigeligen Insekten, vol. i, p. 5. [Note : " Meg." = Megerle von Muhlfeldt, and is but the author of the name in MS.]
Culex ornatus (partim) ; J. F. Stephens, 1825, Zoological Journal, vol. i, p. 454; Hertford. (no?i Culex ornatus, Hoffmgg. ; J. W. Meigen, 1818, op. cit., p. 5. See F. W. Edwards, 191 2, The Entomologist, vol. xlv, p. 277.)
Culex guttatus ; J. Curtis, 1834, British Entomology, vol. viii, p. 537, pi. 537 (but not fig. 9) ; Cobham, Surrey.
Culex albo-punctatus, N. ; C. Rondani, 1872, Bull. Soc. Entom. Italiana, anno iv, p. 31.
Finlaya geniculates, is an easily recognised species. Its black ground- colour, with brilliant white knee-spots and triangular lateral spots on the abdomen, as well as the very pale greenish-yellow markings on the thorax, mark it distinctly from other British species. The larva, too, is very distinct if the " comb " of the eight abdominal segment can be seen ; for the scales of which it is composed form a single line, as in all the larval instar of the British species of Anopheles and A'edes and in the first larval instar of TJieobaldia annulata, Culex pipiens, Ochlerotatus caspius, O. nemorosus and, probably, of all Culicines. In the species of Ochlerotatus the scales of the " comb," in all but the first instar, are irregularly arranged. The teeth of the pecten of Finlaya geniculata are comparatively few, and straighter than in the species of Ochlerotatus. The pecten is comparatively short ; and the anal gills are very long and sausage-shaped.
Finlaya geniculata is a thoroughly sylvan species, and its larva lives, like that of Anopheles plum dens (and often in company with it), in water-filled holes in trees.1 Mr. Burton, of Longner Hall, Shrews- bury, has kept through the following winter, in a wooden tub, eggs which were laid in the autumn of 191 7 ; also a few larvae which hatched before the winter survived. In the spring of 191 8 the eggs hatched, and the larvae, with those that had passed through the winter, completed their metamorphosis and emerged as flies in April. This species, therefore, passes the winter as a larva or in the egg ;
1 Generally Beech trees, but it has been found in Hornbeam, Chestnut, Sycamore, and Ash (F. W. Edwards), and probably occurs in any tree having suitable water-filled holes. It is found also with Orthopcdomyia and Stegomyia, see p. no.
"7
and it is probable that the species of the allied genus Ochlerotatm "li- the same. It is also probable, judging from the respective at which the flies and larvae of various sizes have been found, and from the observations (though few) on the slow rate of growth of the lan that normally there is only one brood of Finlaya geniculate, in the year. Such is not always the case in Ochlerotatus, for 0. caspius, < '. detritus and 0. nemorosus, except in dry years, have at least t broods.
Finlaya geniculata is recorded from Austria, Russia, and Switzer- land (see F. V. Theobald, A .Monograph of the Culicidae or Mosquito. 1901, vol. ii, p. 53, and 1903, vol. iii, p. 191, as Culex lateral* specimens, too, from France (Alpes Maritimes) are in the British Museum Collection; it also occurs in Denmark and Macedonia. The following are some British records : —
Bucks. — Burnham Beeches; (1) 10 and 28, vi, 1907; colld. C. O.
Waterhouse ; (2) larvae and pupae associated with larvae of
Anopheles plumbeus in holes in beech trees, 4, iv, [916; pup
i8, iv, emerged 24, iv ; pupated 24, iv, emerged 30, iv ; pupated
28, iv, emerged 4, v ; pupated 30, iv, emerged 4, v ; colld.
F. W. Edwards. See F. W. Edwards, 1917, Bull. Ent Research,
vol. vii, p. 212. British Museum Collection. Cambs. — Cambridge, in bathroom of Livingstone Hotel ; 20, viii, 191
colld. C. B. Holman-Hunt. Cambridge University Museum
Collection. Cornwall. — Poltesco, N. of Ruan Minor, Lizard district ; 27, v. 19]
colld. Rev. A. E. Eaton. British Museum Collection. Scilly ; vi, 19 19. Colld. K. G. Blair. Essex. — Epping Forest; (1) Epping Thicks; larvae in hollows on
tree-bases; viii, 191 8 ; colld. D. J. Scourficlii :
larvae; colld. A. IV. Baeot ; 10, iv. 191 S. pupated 1, v.
emerged 9, v ; (3) Monkswood ; larvae in hollows on tree-ba
colld. D. J. Scourfield. viii, 1918. /A?///.s\— Gosport ; 22. vii, [892; colld. M. K Thomas. British
Museum Collection. Herts.— Bushey Heath ; 27. vii, 191 2 ; colld F. W. Edwards. B
Museum Collection.
11
98
Cassiobury Park, N. of Watford ; young larvae associated with
larvae of Anopheles plumbeus in hole at base of beech tree ;
21, viii, 1 91 6; colld. F. \Y. Edwards. See Bull. Ent. Research,
1 91 7, vol. vii,pp. 201, 2*12. Kent, — D art ford ; 14, vi, 1912 ; colld. Lt.-Col. Yerbury. British
Museum L olfaction. Middlesex. — Bedford Park, Chiswick ; 17, vi, 19 18. Colld. Dr. C. 'J.
Gahan.
Harrow ; 17, vi, 1914 ; colld. F. W. Edwards. British Museum
Collection.
Regent's Park, London, N.W. ; 4, viii, 191 5; colld. F. W.
Edwards, British Museum Collection. Oxon. — Stokenchurch ; 13, viii, 1907; colld. G. H. Verrall. British
Museum Collection. Shropshire. — Longner Hall, S.E. of Shrewsbury; 31, v, 1908, and
5, viii, 1918 ; flies; see also record above of eggs and larvae;
colld. R. F. Burton. British Museum Collection.
V. TAEXIORHYNXHUS, Arribalzaga.
Taeniorhynchus, nov. gen. ; F. L. Arribalzaga, 1891, Dipterologia Argentina, 1 ; Revista del Museo de la Plata, vol. i, p. 374, and vol. ii, p. 147. Genosyntypes, Culex taeniorhynchus ^ Arribalzaga, non Wiedemann, Taeniorhynchus confinnis, n. sp., and Taeniorkynchus fasciolatus. n. sp. Genolectotype, Culex titillans F. Walker, in J. E. Gray, 1848, List of the specimens of Dipterous Insects in the collection of the British Museum, part i, p. 5 ( = Culex taeniorhynchus Arribalzaga, non Wiedemann).
1. Taeniorhynchus richiardii (Ficalbi). Figs. 24, 26, 35, 38, 74.
Culex Richiardii, n. sp. ; E. Ficalbi, 1889, Bull. Soc. Ent. Italiana, vol. xxi,
P- 5°-
Taeniorhynchus richiardii is easily distinguished from all British gnats except Theobaldia annulata by having a pale ring in the middle of the first tarsal joint of the hind leg. And the wings, speckled with very broad scales, dark mixed with light, render it very easily distinguished from Theobaldia annulata. The most remarkable feature,
however, in Taeniorhynchus richiardii is th< >n of the larva, which
not only has no pecten, hut is of a peculiar shape, the true sip being exceedingly short, and its apparently pointed tapering end b< formed of the ventral pair of the valves that in a normal siphi i the aperture. The siphon is adapted for piercing the of sub-
merged plants,1 and for exploiting the air contained in them and thus obviating the necessity of periodic journeys to the surface for breath. Edwards has observed that this species spends the winter as a n< arly full-grown larva.- The pupa also is adapted to a submerged life, and pierces the roots of grass with its pointed thoracic trumpets. The fly appears about midsummer, and though widely distributed, does not seem to be very common. It was originally described from Italy ; specimens from Palestine are in the British Museum Collection ; and Waterston records it from Macedonia (Bull. lint. Research, i vol. ix, p. 8). British records are as follow
Cambs. — Wicken, N.E. of Cambridge; 2, vii, ioi;; colld. F. W.
Edwards. British Museum Collection. Dorset. — Littlesea, Studland ; 2, viii, [911 ; colld. Rev. E. A. E;
British Museum Collection. Durham. — Gibside, S.W. of Gateshead ; 10, viii, 19 16 ; colld. R. S.
Ba<mall. British Museum Collection. Hants. Church Farm, near Hook, E. of Basingstoke, Hants. ; 17, vii,
1 91 2 ; colld. F. W. Edwards. British Museum Collection. Herts. — Letchworth ; larvae. Colld. /•". //'. Edzvards ; Jan. [9]
Kent. Dymchurch, S.W. of Ilythc ; in an outhouse, with female Anopheles maculipennis , 25, vii, [918. Colld, G. Walt
Wye, N.E. of Ashford ; indoors ; colld. Theobald. F. I '.
Theobald, 1903, A Monograph of the Culicidae or
vol. Hi. p. 269. Middlesex. Ealing; 26. vii. [912; colld. II. Campion. Bn Museum Collection.
1 Glyceriafluitans',xx F. W. Edwards, 1919, and Typha; see C. Wi senberg-Lund, 1918,
- For a detailed account of this Ian Monthly Magazin 5, vol. v, 1-. 83. Also, C. Wes(
belige Meddelelser fra Dansk Naturhi ing in Kjppenhavn, ■■
II 2
IOO
Norfolk. — Norwich and the Norfolk Broads ; obs. Dr. Long. See F. V. Theobald, 1903, A Monograph of the Culicidae or Mos- quitoes, vol. Hi, p. 269.
Shropshire. — Longner Hall, S.E. of Shrewsbury ; 30, vii, 1918. Colld. R. F. Bur ton.
Sussex. — Angmering Ponds, S.E. of Arundel ; colld. Rev. A. E. Eaton. See F. IV. Edwards, 19 12, The Entomologist, vol. xlv, p. 261.
Patching Pond, N.W. of Worthing; 9, ix, 1907; colld. Rev. A. E. Eaton. British Museum Collection.
Warwickshire. ^-Sutton Coldfidd ; colld. R. C. Bradley. See F. W. Edwards^ 191 2, The Entomologist, vol. xlv, p. 261.
VI. THEOBALDIA, Neveu-Lemaire.
Theobaldia, nov. gen. ; M. Neveu-Lemaire, 1902, Comptes Rendus Heb. des Se'ances et Memoires de la Soc. de Biologie, vol. liv, pp. 133 1-2. Genotype, Culex annulatus, Schrank.
1. Theobaldia annulata (Schrank). Figs. 8, 21, 33, 36, 76, 123-5.
Culex annulatus; F. v. P. Schrank, 1776, Beytriige zur Naturgeschichte,
p. 97. Culex affinis, Mihi ; J. F. Stephens, 1825, Zool. Journ., vol. i, p. 452;
Hertford ; in June. Culex calopus ; J. F. Stephens, 1825, loc. cit. ; near London (non Culex
calopus, Hofifmgg. ; J. W. Meigen, 1818, Systematische Beschreibung
der bekannten Europaischen zweifliigeligen Insekten, vol. i, p. 3).
Specimens thus labelled in Stephens' Collection in British Museum.
Theobaldia annulata is one of the commonest and most easily distinguished of British gnats. Its great size, boldly-contrasted black and pale-cream colouring, as well as its domestic habits, force it upon the attention. With Anopheles maculipennis it is known from all other British species by having spots on the wings. They are formed by the aggregation of dark scales. From A. maculipennis it may be known by its burly build, as well as by its banded legs and abdomen. Culicella morsitans and C. fumipennis also have a tendency for the aggregation of wing-scales into spots, but this is only a tendency, and the characters given on p. 30 indicate how these two species can
easily be distinguished from Tlteobaldia annulata. The larvae of the two species of Culicella, and that of Theobaldia annul at a, differ from the larvae of other species of British gnats in the position of the tufl hair at the proximal end of the siphon instead of near the m And the pecten-teeth of T. annulata% produced into hair-like termii tions, distinguish the larva of this specie- from those of Culicella morsitans and C. fumipennis (figs. 76, [23 -5).
Theobaldia annulata, like Anopheles maculipennis, and i ule* /\r. (and often in company with these), winters as a female fly in cell.. outhouses, etc. ; and may be troublesome in mild weather in the winter, by becoming active owing to the warmth and biting in the house. It is possible that in exceptionally mild winters some lan may survive, since they have been recorded at dates very late in the year. Some eggs which hatched in captivity in the British Museum 2nd Sept., 1918, passed through several instar, but most died before the fourth instar was attained, and none pupated. Their death, however, may have been due to unnatural conditions or unsuitable food. On the other hand, some very young larval Anoph plnmbeus, taken in Epping Forest and Culross, Fifeshire. in late- summer, 191 8, having attained the fourth larval instar are still alive at the present time (Feb. 1919). Larval Theobaldia annulata is some- times found with Culex pipiens in water-butts ; and. as far as I am aware, these are the only British species which are found in what may be called domestic waters.
Theobaldia annulata occurs throughout Europe, in X. Afri and in Mesopotamia there is a variety apparently adapted to desert conditions, the white scales becoming yellow, and the black- brown. The American records probably refer to /'. maccrack .nil T. dugesi (see H. Dyar, L. Howard and F. Knab, [915, Mosquit \. of Central America and the West Indies, vol. iii. pp. 404 and | Specimens in the British Museum Collection have been obtained from Norway, Switzerland, Southern France, Cyprus, and Moroco Miss A. L. Lang has sent me a specimen from M< nastir ; Mr V. I .n records it from Mikra in the Salonica district Bull. Ent. R ch, 1918, vol. ix, p. 91 ; and Major E. E. Austen, 1 tells me h< with one specimen in Palestine.
In Britain the species has been collected from soman]
102
that it would serve no purpose to enumerate them. But it is worth noting that specimens from as far north as Inverness-shire and Aberdeen are in the British Museum Collection.
VII. CULICELLA, Felt.
Culicella, n. gen.; E. P. Felt, 1904, New York State Museum Bulletin 79, p. 39 1 C. Genotype, Culex dyari, Coquillett.
I. Culicella morsitans (Theobald). Figs. 23, 31, 34, 37, 59, 69, 71, 77.
Culex morsitans, n. sp. : F. V. Theobald, 1901, Monograph of the
Culicidae, vol. ii, p. 8, pi. xx, fig. 79. ? Culex dyari, sp. nov. ; D. W. Coquillett, 1902, Journ. New York Ent. Soc.
vol. x, p. 192.
Culicella morsitans and C. funtipennis are very similar species hardly to be distinguished as flies, but having quite distinct larvae. The blunt abdomen, the short first hind-tarsal joints, and nearness of the posterior cross-vein to the other cross-veins characterise these two species of Culicella and separate them from the other British gnats except Theobaldia annuldta. That species, however, besides having spotted wings, has a median pale longitudinal band on the second abdominal segment and the posterior cross-vein almost in a line with the mid cross-vein, characters not possessed either by Culicella morsitans or C. fumipennis. In C. morsitans there are very few, if any, white scales on the proboscis of the female (fig. 69), and in the male the first foreJtarsal joint is decidedly longer than the remaining four joints ; the pattern, too, on the underside of the male abdomen is generally diffused rather than clearly marked (fig. 71). In the larva (fig. 77) the axis of the pecten is nearly parallel with that of the siphon, and there are no single scattered spines on the siphon as there are in C. fumipennis, the axis of whose pecten is oblique with that of the siphon. (Note : The siphons of the two species are figured by F. W. Edwards, 19 12, The Entomologist, vol. xlv, p. 262, figs. 3, 4, but, unfortunately, the names have been transposed in the legends.) According to F. W. Edwards, the larvae of both British species of Culicella feed mainly at the bottom and prefer open pools. When disturbed they wriggle beneath the leaves. Evidently they shun the surface, and may well be on the way to developing similar habits to
Taeniorhynchus. Mr. Edwards suggests that it is even possible thai
that genus may have been derived from Culicella.
C. morsitans appears to be mainly a British . and in Britain
to be somewhat commoner than C. fumipennis. The type-sp< is
from Eridge, Sussex. There are specimens in the British Museum Collection from Ghent and Southern France, and de Meijere • it
from Holland (Tidschrift v. Ent., nil 1. vol. liv, p. [38). It occurs
in Denmark and Macedonia. British records are as follow
Bucks. — Burnham Beeches; 10, vi, 1907; colld. C. O. Waterhouse ;
6. v, 19 1 4 ; colld. F. W. Edwards. British Museum Collection. Essex. — Epping Forest; larvae; 21, iv, 1918 ; one pupated 24. iv, and emerged 1, v; and another pupated 23, iv, and emci 29, iv ; colld. Lt. Tickner Edwardes, R.A.M.C. ; pupa, 13, v, 1 emerged 16, v. 191 8 ; colld. Miss Cheesman.
Rochford ; 11, 12, and 15, vi, 1907 ; colld. Rev. A. I'.. Eaton. British Museum Collection. Hants. — Brockenhurst ; 30 and 31, iv. and 9, 15, and 28, v. colld. C. O. Waterhouse. British Museum Collection.
Lyndhurst ; colld. Lt.-Col. Yerbury. British Museum Collect: Hunts.— Wood Walton Fen, E. of Ramsey; 13-15, iv, [914; colld.
F. W. Edwards. British Museum Collection. Middlesex. — Harrow Weald Common; pupa; 28. iv. 1913 ; olid.
F. W. Edwards. British Museum Collection. Norfolk.— Ormesby. N. of Great Yarmouth ; 25. vi. [918 ; colld «".. II.
Yerrall. British Museum Collection. Shropshire. — Longner Hall, S.E. of Shrewsbury ; in garden, i6,vi,
5, vii, 191 8; colld. R. F. Burton. British Museum ion
S,^;/^— Newmarket ; 26. viii, 1908; colld. G. II. Yerrall. B
Museum Collection. .S///7T/.— Mitcham Common ; larvae; 3, v. [918, pu| Il8,
emerged 15, v, [918 ; pupa collected 3, v. 1918, emerged '• \ . : Colld. Miss L. E. Cheesman.
Woking. See /■'. W Edzvards, 1912, /'■ vol. xlv, p. 262. Sussex— Angmering Ponds, S.E. of Arundel ; 4, vii, 1 A. E. Eaton. British Museum Collection.
104
Eridge, S. of Tunbridge Wells, Kent ; type-specimen of C?ilex morsitans ; colld. G. H. Verrall. British Museum Collection.
Patching Pond, N.W. of Worthing ; 10, ix, 1907 ; colld. Rev. A. E. Eaton. British Museum Collection.
Wales. — Llanidloes, Montgomeryshire; 24, vii, 1918. Colld. R. F. Burton.
2. Culicella fumipennis (Stephens). Figs. 70, 72, 78.
Cukx fumipennis, Mini. ; J. F. Stephens, 1825, Zoological Journal, vol. i,
P- 453- Culicada Theobaldi, n. sp. : J. C. H. de Meijere, 1911, Tidschrift voor Entomologie, vol. liv, p. 142, pi. ix, figs. 10-16. See F. W. Edwards, 1 91 2, The Entomologist, vol. xlv, p. 277.
The white scaling at the sides of the proboscis in the female (fig. yo), and the length of the first fore-tarsal joint and the pattern of the underside of the abdomen in the male (fig. 72) are the only characters hitherto observed whereby the imago Culicella fumipennis can be distinguished from C. morsitans (see pp. 44-5). And since these differences are matters of degree, they are by no means as certain guides for determination as is desirable. I have not been able to discover any differences in the male genitalia. The larvae, however, have very different siphons (see figs. 77-8), and can be distinguished at a glance under sufficiently high magnification. It would be of great interest to determine by numerous experiments if these two species always bred true, and that they were not one species with a dimorphic larva. Also, since the genitalia are so similar, whether they would interbreed, and in that case whether the siphons of resulting larvae would exhibit dominance or mixed characters ; and in the former case whether the 3 : 1 Mendelian proportion would occur in the second generation.
Culicella fumipennis appears to be nearly as common as C. morsitans and as widely distributed. De Meijere records it (as Culicada TJieobaldi) from Holland, Noe from Italy, and Waterston from Macedonia.
British records are as follows : —
Bucks. — Burnham Beeches; larvae and flies; 6, v, 1914; colld. F. W. Edwards. British Museum Collection.
Dorset.— Burton Mere; 27, v, 1910; colld. Rev. A E. Eaton 6 itish
Museum Colli xtion.
Littlesea, Studland ; 2, viii, 1 « # 1 1 ; colltl. Rev. A. E. 1
British Museum Collection.
Studland; 21, v, 1912 ; colld. Lt.-Col. Yerbury.
Museum C ollection. Hants. — Brockenhurst ; flies and larvae ; 15, v. [904 ; 3, IO, 12.
vi, 1905 ; 15, vi, 1906; colld. C. 0. Waterhouse. British May
Collection. Middlesex. — Harrow-on-the-Hill ; 14, v, 1905; colld. W. D. I.
British Muse inn Collection.
London, British Museum (Nat. Hist), Diptera Room ; 4. ix,
1916 ; colld. F. W. Edwards. British Museum Collecti Shropshire. — Longner Hall, S.E. of Shrewsbury ; in garden. [<
1908; colld. R. F. Burton. British Museum Collection.
Shrewsbury ; on windows in Board Room, Shrewsbury Infirmary ;
3, ix, 1910 ; colld. R. F. Burton. British Museum Collecti Surrey. — Ripley, N.E. of Guildford ; type-specimen ; colld. I F
Stephens. British Museum Collection. Wales. — Llanidloes, Montgomeryshire; 24, vii, [918. Colld. R. F,
Burton. Scotland. — Dingwall, Cromarty ; 31, v, 191 1 ; colld. Lt-Col. Yerbury.
British Museum Collection.
Invcran, Sutherland ; 17, vii, [886; colld. (i. H.Verrall. B
Museum Collection.
VIII. CULEX, Linnaeus.
Culex; Linnaeus, 1758, Systema Naturae, Regnuni Animate, editio p. 602. Genpsyntypes, C. pipiens, C. hi fur cat us, C /•■ C. reptans and C. stercorals. Genolectotype, C. pip D. W.
Coquillett, 1910, Proc. United States National Museum, vol. xxxvii,
P- 5-9-
1. Culex pipiens Linnaeus.
Figs. 1, 16, 19, 22, 32, 79, 121
Culex pipiens ; Linnaeus, 1758, Systema Naturae, Regnum Anin
decima, p. 60 2. Culex bicolor; J. F. Stephens, 1825, Zool Journal, »
from Hertford. (Probably Culex J. W. Meig
io6
Svstematische Beschreibung der bekannten Europaischen zweifliigeligen Insekten, vol. i, p. 9. See F. W. Edwards, 1912, The Entomologist, vol. xlv, p. 277.)
Culex lutes cms ; }. F. Stephens, 1825, loc. cit.; from Darenth. (non Culex lutes cens ; J .C. Fabricius, 1775, Systema Entomologiae, p. 800. See F. W. Edwards, 1912, The Entomologist, vol. xlv, p. 277.)
Culex punctatus ; J. F. Stephens, 1825, loc. cit. ; no locality is recorded, (non Culex punctatus ; J. AW Meigen, 1818, Systematische Beschreibung der bekannten Europaischen /.weirliigeligen Insekten, vol. i, p. 9. See F. W. Edwards, 191 2, The Entomologist, vol. xlv, p. 277.)
Culex marginalis, Mihi. ; J. F. Stephens, 1825, op. cit. p. 455 ; one female ; London See F. W. Edwards, 191 2, The Entomologist, vol. xlv, p. 277.
Culex rufus ; J. F. Stephens, 1825, op. cit., p. 456 ; from Hertford (common). (non Culex rufus, Hoffmgg. ; J. W. Meigen, 18 18, Systematische Beschreibung der bekannten Europaischen zweifliigeligen Insekten, vol. 1, p. 7. See F. W. Edwards, 1912, The Entomologist, vol. xlv, p. 277.)
Culex domesticus (partirh) / J. F. Stephens, 1825, op. cit., p. 455 ; from Hertford. (Probably Culex domesticus ; E. F. Germar, 18 17, Reise nach Dalmatien und in das Gebiet von Ragusa, p. 290.) Three specimens under this name in Stephens' collection in the British Museum are Culex pipiens and one Culex nemorosus.
Culex sylvaticus ; J. F. Stephens, 1825, op. cit., p. 454; one specimen, in June, from Coombe Wood, (non Culex sylvaticus; J. W. Meigen, 18 18, Svstematische Beschreibung der bekannten Europaischen zweifliigeligen Insekten, vol. i, p. 6, which is Ochlerotatus nemorosus, q.v.)
The male Culex pipiens may be known at once from other British gnats, except C. apicalis, by the pointed palpi which curl upwards through an angle of about 90 (fig. 19). The female ma}' be known from Ae'des and Ochlerotatus by the blunt abdomen (fig. 16) and simple claws ; and from Taeniorhynchiis, Theobaldia and Culicella by the long first hind-tarsal joint (fig. 32). The long fork and short stalk of vein 2 of the wing is also an easily seen character distinctive of Culex. The creamy colour of the pale abdominal bands and their basal position distinguishes both sexes of Culex pipiens from C. apicalis. The larva is known by its long slender siphon (less slender than that of C. apicalis) and several scattered hair-tufts with few hairs.
Culex pipiens is quite the commonest British gnat, and is abundant everywhere. It is the more noticeable, as it frequents houses and, with Anopheles maculipennis and Theobaldia aunulata. spends the winter as an impregnated female fly in the shelter of buildings.
Any collection of water that is not too foul serves as a breeding-place. Water-butts and zinc cisterns, as well as pond.-, in various situatii in fact, any stagnant water appears to satisfy the larv pipiens. One unusual situation is recorded by A. Macdonald, jun.. from Culross, Fifeshire. He found larvae in collections of water in a disused saw-pit in what had been a copse situated on a m<;or ; but the trees had lately been cut down, so that where the water was there was now no shelter at all. The water was dark-coloured, but cle; Foreign records show Culex pipiens larvae to be still less particular in their breeding-places. H. Dyar, L. Howard and F. Knab (1915, Mosquitoes of North and Central America and the West Indies, vol. iii, p. 367) say that the larvae are able to thrive in highly polluted water, and quote catch-basins of sewers and water highly charged with the refuse from slaughtered animals as localities for them. They quote Ficalbi as recording the larvae of Culex pipiens from fonts consecrated water in churches and in sulphurous water ; and J. Waterston (1918, Bull. Ent. Research, vol. ix, p. 10) found them in Macedonia in an artificial washing-pool amid soap-suds, and in extremely foul-smelling, but quite clear, rocky pools of a sewaj effluent. It is probable, then, that in England Culex pipiens is more particular in its breeding-places, but for lack of observation it is not credited with such foul propensities.
C. pipien s occurs throughout Europe, in northern Africa. E. Afri Madagascar, and restrictedly in X. America. From the last-mention fact, Dyar, Howard and Knab consider that the species has been introduced into X. America from Europe. It is worthy of n< I that Culex fatigans. a species so much resembling Culex pipiei the only satisfactory characters for distinguishing the two sped in details of the male genitalia, has a very wide geographi tri-
bution in the warmer parts of the world, and has been records I 1 ■'. V. Theobald, 1901, A Monograph of the Culicidae or Mosquitoes, vol. ii. p. 154) from Spain and Portugal. Now it is evident that, since the two species are so much alike that it needs a microscope-preparati before their differences can be seen, it may easily happen that • fatigans maybe present in a country without being detected.: for il C. pipiens is common. C. fatigans will not be sought possible that if C fatigans were to extend its range it mij
ioS
long time be unnoticed. The practical interest of C. fatigans is that it conveys (and presumably can transmit) the worms that cause filariasis and the organism that causes dengue fever. It is desirable, therefore, that C. pipiens should be closely watched in case C. fatigans extended its range ; and the possibility should not be forgotten of C. pipiois acquiring the disease-bearing habits of C. fatigans where the range of these species overlap, and by this means spreading the diseases concerned over its own range.
Culex pipiens, Linnaeus ; var. doliorum, Edwards.
Culex pipiens, var. doliorum (nov.); F. W. Edwards, 191 2, The Entomo- logist, vol. xlv, p. 263.
Culex nigritulus, Zetterstedt ; F. V. Theobald, 1901, A Monograph of the Culicidae or Mosquitoes, vol. ii, p. 140.
non Culex nigritulus ; J. W. Zetterstedt, 1850, Diptera Scandinaviae, vol. ix,
P- 3459-
Edwards describes as a variety of Culex pipiens a form which is much smaller, darker, and having a thorax without any reddish tint, and recognises it as identical with British specimens referred by Theobald to Culex nigritulus, of Zetterstedt. Theobald's specimens were from larvae living in water-butts, but the locality is not mentioned. Edwards' type-specimen of his variety doliorum was also reared from a larva which with others was " swarming in water-barrels at Kings- wear, S. Devon." They were found in October, 191 1. A single specimen from Bushey Heath, Herts, and collected by F. W. Edwards, 27, vii, 191 2, is in the British Museum Collection.
2. Culex apicalis, Adams.
Figs. 73, 129.
Culex apicalis, n. sp. ; Adams, 1903, Kansas Univ. Sci. Bull., vol. ii, p. 26. Culex pyrenaicus, n. sp. ; Brolemann, 1919, Ann. Soc. Ent. France, vol. lxxxvii,
p. 427. Culex hortensis, Ficalbi ; F. W. Edwards, 191 5, Entomologist's Monthly
Magazine, ser. 3, vol. i, p. 167. non Culex hortensis; E. Ficalbi, 1889, Bull. Soc. Ent. Italiana, vol. xxxi,
p. 217.
Culex apicalis resembles the more southern and eastern species C. hortensis, but has broader wing-scaling and. no white spot at the distal end of the tibia. A single specimen of this species was taken
109
by F. Jenkinson at Logie, Elgin, X.B., n, ix, [911, and is now in th< Cambridge University Museum. The type-specimen came from N. America, and that of C. pyrenaicus from the Pyrennee . and I latter form has also been taken at Rambouillet and la Creuse in France (see J. Ville'neuve, 1919, Bull. Soc. Ent. France, p. 5$
IX. ORTHOPODOMYIA, Theobald.
Orthopodomyia^ nov. gen.; F. V. Theobald, 1904, I Entomolog
vol. xxxvii, p. 236. Genotype, O. alipes, n. -p.
I. Orthopodomyia albionensis, MacGregor.
Figs. 1 30- 1 2.
Orthopodomyia albionensis, sp. nov.: M. E. MacGregor, 1919, Journ. k
Army Medical Corps, vol. xxxiii, p. 451, and plate. ? Culex pulchripalpis, X.; C. Rondani, 1872, Bull. Soc. Ent. Ital., anno
P- 3i.
? Culex pulchripalpis, Rondani (1872) ; E. Ficalbi, 1899, Bull. Soc. Ent. Ital.,
anno xxxi, p. 220. non Culex pulchripalpis ; F.V.Theobald, 1901, A Monograph of the Culicidae
or Mosquitoes, vol. ii, p. 16, which is Ochlerotatus ca spins, q. v.
Orthopodomyia albionensis is easily distinguished from all other British gnats by the long palps of the female (fig. 130) and by the fourth tarsal joint of that sex (fig. 131 ) which, at least in the fore-l< is not longer than broad. The general black ground-colour with brilliant white (not creamy) markings also distinguish both sexes from all the British forms except Finlaya geniculates and Stegomyia fascia (added to the British list while this work was in the pr \>. 112.
The complete white abdominal bands and white-banded tarsi distinguish it from the former, and its larger size and three pairs (instead of two pairs) of white longitudinal stripes on the dorsal surface of the thorax distinguish it from Stegomyia fasciat ell as
the absence of the silvery-white lateral row of abdominal s species, and the larva has no pecten on an otherwise norma n
(fig. T32).
In July of this year ( 1 9 1 9 ) , Major A. Macdonald collected some larvae in Epping Forest from a tree-hole from which he had forn: ■obtained the larvae of Anopheles plum be us. They were reared by
I IO
Capt. M. E. MacGregor at Sandwich, Kent, and the emergent flies were mosth- Finlaya geniciilata. Among them, however, appeared four Ortkopodomyia, described by MacGregor as a new species. But Rondani's original diagnosis of Culex pulcliripalpis, and Ficalbi's later more detailed description do not leave the matter free of doubt ; and it may be that the Epping Forest specimens are of Rondani's species Until it is possible, therefore, to compare Italian with the English material, it is better to accept MacGregor's name for this form.
rEKzr-
FiG. 130. — Head of female Ortkopodomyia
albionensis, showing the rather long palps.
Fig. 131. — End of fore-tibia and fore-tarsus of female of the same species, showing short fourth tarsal joint.
Through the kindness of Major A. Macdonald and Capt. M. E. MacGregor, a specimen of each sex of Ortkopodomyia albionensis is in the British Museum. On the 31st July, Mr. F. W. Edwards and Capt. MacGregor visited the tree-hole and collected a good deal of material. That brought back by Mr. Edwards yielded only Finlaya geniculates ; but from Capt. MacGregor's material emerged a few Ortkopodomyia and two specimens of Stegomyia fasciata, a second mosquito new to Britain from this tree-hole. On another visit, on nth August, to the same tree-hole, Mr. Edwards secured a single
larva of 0. albionensis in the fourth iristar, and five pupae, three of which he reared to the imago-stage. Again, in September, Mr. 11. Main I three more larvae, one in the second and two in the third instar, i to the spot in Epping Forest whence the others were obtain* d. These are still (Jan. 1920) alive, one in the third and the other two in the fourth instar, and it is likely that will hibernate in this condition.
It is a great encouragement to collectors that, while this work v in the press, this and two other species new to Britain, namely, Ochlerotatits curriei (see p. 84) and Stegomyia fasciata (see p. ii2> have been discovered.
Fig. 132. — Siphon ;ind comb-scale of the fourth-instar of larva of same S]
IV. REPUTED, DOUBTFUL, AND FOSSIL BRITISH SPECIES.
Stephens (1825, Zoological Journal, vol. i. pp. 452-456) re< as British several of Meigen's species which have not since been found. Fortunately, Stephens' collection is in the British Museum, and his determinations have been revised by Mr. F. W. Edwards (see The Entomologist, 1912, vol. xlv, p. 2771. All are referable to known British species. References to these are included in the synonymy under the account of the species to which they refer.
Besides these there are the following n of foreign
Britain : —
Cuhx lutescens; J. C. Fabricius, 1775- Systems Entomologii
Recorded as British l.y F.V.Theobald, 1901, A Monograpl < the
I 12
( ulicidae or Mosquitoes, vol. ii, p. 168, from Kingston-on-Thames, in 1S85 ; but the specimen no longer exists. Also by G. H. Verrall, 1888, A List of British Diptera, p. 10.
Stegomyia fasciata (Fabricius). Culex fas ciatus : J. C. Fabricius, 1805, Systema Antliatorum, p. 36. Two specimens of this mosquito emerged from the pupal material (otherwise Finlaya geniculata) collected by Capt. M. E. MacGregor from the tree-hole in Epping Forest from which the larvae and pupae of Orthopodomyia albionensis had already been obtained (see above). Stegomyia fasciata is the mosquito concerned in conveying Yellow Fever; and, being a ready breeder, is reared extensively in research laboratories in England. It would not, therefore, be a matter for surprise had escaped specimens of the fly been taken from the neighbourhood of laboratories. But to find it in the larval and pupal stages in Epping Forest is another matter, and it appears likely that, if no mistake has been made, this is a genuine case of the introduction of a foreign species. It will be interesting to note whether the species will survive the winter in the locality where it appears to be established. Stegomyia fasciata differs in general appearance from all other British forms, except Finlaya geniculata and Orthopodomyia albionensis, \x\ being a black species with brilliant white markings ; and from the two species mentioned in being much smaller and having a pair of sickle-shaped white bands on the thorax, a second pair of straight, yellowish, longitudinal lines between these, and a lateral row of silvery-white spots on the abdomen in addition to the usual banding. Orthopodomyia albionensis has three pairs of very narrow, white, longitudinal lines on the thorax, Finlaya geniculata has a median, pale, greenish-yellow line and a pair of similar lateral lines on the dorsal surface of the thorax, and lacks the white tarsal bands of the other two species (see M. E. Macgregor, 191 9, Bull. Ent. Research, vol. x, p. 91).
' Before leaving- the subject of reputed British species, it is worthy of remark that there is a widespread belief in the occurrence of foreign gnats (" mosquitoes " they are generally called in this connection) intro- duced into this country by means of ships. The belief appears in letters written to the Museum, in entomological literature (see the case of the "Norway Mosquito" recorded in the Entomological Monthly Magazine, 1895, p. 227, which was merely Ochlerotatus caspius), and finds perennial expression in the Press; there is an echo of it in Theobald's remark on Culex pulchripalpis (see under Ochlerotatus
'13
caspins, p. 83); and it is a possible explanation of the remarkab and isolated occurrence of Culex apicalls, an Ai in and Medit
ranean species, in Elgin (see p. 10S), and the single case of Stegi m fasciata quoted above. But. apart from the fact that, th means impossible, such introduction is uhlikely,1 there is n ve
evidence that any gnat taken in Britain was introduced, and all sup- cases (except the two last mentioned) that have been in proved to be ordinary British species. Such rumours, then, should treated with scientific scepticism, and conclusive evidence demand
Though beyond the original intention of this work, it is of inter to observe that at least three species of gnat are found sils in
Britain. These are from the Oligocene of Gurnard Bay, W. of C< ro Isle of Wight, and are described by T. D. Cockerell. 1915, Pi United States National Museum, vol. xlix, pp. 488-9, pi. Ixi, fig. 12. and pi. lxii, figs. 1 and 2. They are named as follows : —
Culex protolepis, Cockerell, op. fit., p. 488, pi. lxii, fig. 1. Culex pro for Ainus, Cockerell, op. cit., p. 48S, pi. lxii, fig Culex petrifactellus, Cockerell, op. cit., p. 4S9, pi. Ixi. fig. 12.
From the figures and descriptions of these forms it is evident th they are Culicidae, but a more exact determination is not possible. To assign them to the genus Culex is but conjecture.
Gnats have also been described from the Baltic amber, which probably is also Oligocene in age. And since Baltic amber is frequently picked up on our eastern coasts, it is possible that gnat-fauna may be found in Britain.
V. EVOLUTIONARY AXI) CONCLUDING
REMARKS.
It is evident from the foregoing account that there is much yet to be found out about British Mosquitoes. About their structure, for there may be many other differences than those given in the diagnostic tables, and these mav be more definite and more seen than those characters which are given ; besides, the first two
ept in the case of the "cultivated
U4
larval instar of Ochlerotatus detritus have not been described ; and only the last larval instar of Taeniorkynchus richiardii, Aedes cinereus, Ochlerotatus vexans, 0. ivaterhousei, 0. auuulipes, 0. rusticus, Culieella
morsitans, C. fumipeuuis and Orthopodoiuyia albionensis ; and no larval stasre of Ochlerotatus curriei. And about their habits, both as flies and larvae ; the times of appearance of the former, their distribution, the stations they mostly frequent, their enemies and other adverse circum- stances affecting them, the kind of prey they prefer (for instance, Culex pipiens is said especially to attack birds), and their mating habits ; and, in observing the larvae, the kind of water they like best, the amount of impurities they can stand, the nature of their food and of their foes, and the behaviour in the winter of those that hibernate, are instances of what needs to be done. The remarks on pp. 5-1 1 illustrate the directions and scope of some of the conclusions to be drawn from the habits of mosquitoes. And, though a knowledge of the structure of each instar of even' species is of immediate use for identification, it is of still greater interest if it points to possible conclusions concerning the evolution of gnats. The study of post-embryonic growth-stages as affording evidence of the phylogeny of any group is becoming more widely pursued by biologists, and has been applied with encouraging results especially by those whose work lies among fossil organisms. And one of the commonest occurrences met with by palaeontologists is that of homceomorphy both in convergent and in parallel evolution — homoeomorphs being organisms closely resembling one another, yet having a different ancestry manifested in differing post-embryonic growth-stages. Hence, if two gnats resemble one another so closely that their separation is a matter of considerable trouble, it is not surpris- ing to find their larvae differing considerably, as in Culieella morsitans and C. fumipennis. Again* it is probable that such larvae, in common with other more distantly-connected species, will resemble one another more closely in the earlier instar. Thus, a larval difference (unless, as in Taeniorkynchus, the larval peculiarity is obviously the result of direct adaptation to a peculiar environment) is probably of more significance than a difference in the imago. This principle has been recognised as fundamental by American authors, notably by Dyar and Knab, and they accordingly classify mosquitoes primarily with regard to their larval characters.
H5
A glance at the British forms will show the value of some of th< larval characters. It is evident that the genus Anopheles differs more from the other genera of gnats than these d<» among themselves : but the larval differences are more striking than those of the imago. And even the first larval instar of Anopheles differs considerably from the first larval instar of a Culicine — notably in r> [ng no siphon, in
having anterior clypeal hairs, float-hairs and the scaler of the comb united basally. It is even possible that the " secondary comb " of the first instar Anopheles with its separated scales is the homologuc of the comb of the Culicines. It is likely, then, that Anopheles diverged from the main stock before this had divided into various Culicine lineages. The first instar (as far as it is known) of the various Culicine genera have the hair on the siphon approximately in the position of the hair- tuft in the later instar ; and this renders it likely that the genera A Finlaya and Ochlerotatus diverged along one line, Theobaldia, Culicella, and possibly Taeniorhynchus along a second line, and Cnlex alon third line. It is evident from an examination of the first larval instar of various species that the arrangement of the comb-scales in a single disconnected row is a primitive one. This primitive condition is re- tained in Aides, Finlaya and Taeniorhynchus throughout their larval life. It is of interest to note that this primitive line has apparently independently broken up into a triangular patch with the scales irregularly arranged in Ochlerotatus, in Theobaldia (and presumably Culicella) and in Cnlex. From the first instar, too, it is seen that the arrangement of the post-antennal hairs is approximately in a line. In the second, third and fourth larval instar of Ochlerotatus, the mill post-antennal hair has moved forward and inward, showing that in this character Ochlerotatus has advanced beyond the other allied genera.
The arrangement of the larval hairs has been considered from an evolutionary point of view. What of their form ? Culicid larvae are remarkable for the extraordinary variety of form displayed in the hairs springing from the integment. These may be apparently simple, split at the end, slightly branched, once or twice bifurcate, pinnately branched or feathered, dendroid, tufted, with flattened laminae forming rosettes (as in float-hairs) or fringed scales (as in the comb), stiffened so as to be bristle-like or hardened into a spine
i :
n6
or tooth. It is reasonable to suppose that these are all modifications of a simple hair, and that various degrees of branching (from mere splitting of the end to a fringed scale or a tufted hair consisting of several sub-equal branches united at the base, and themselves having tiny secondary and pinnately-arranged branches) have been imposed upon the simple hair during evolution, and that the general develop- ment of a hair is an anagenesis from more simple to more complex. But in certain cases, hairs may be seen to be secondarily simple and to be in catagenesis or declining evolution. Such are the anterior clypeal hairs of Anopliclcs plnnibens in the last two instar. Those of the third instar (fig. 88) are more complex than those of the fourth (fig. 82), and those of the second (fig. 94) than those of the third instar. It is probable, too, that the smooth antennae of Anopheles plumbens, Finlaya genicn/ata, and OrtJwpodomyia is a secondary con- dition correlated with their life in tree-holes; that is, that the appressed spines or scales were originally present, but were lost during evolution. There is, however, no ontological evidence in this case.
It is possible, while in all the cases hitherto mentioned, the h'air, scale, or tooth is derived from a single hair, the pecten-teeth, on the contrary, are compound in origin, and that each tooth is comparable with the comb of the eighth segment. In the first instar of O. neino- rosus the more distal pecten-teeth may have several smaller denticles on each side of a larger one, and are reminiscent of the very minute rows of graduated teeth that cover the siphon and chitinous " saddle " of the ninth segment.
It is often asked of what use to the organism is the comb or the pecten. For that matter, what use has been discovered for any of the marvellously-shaped hairs with which the larva is so abundantly adorned ? The function of the palmate hairs of Anophe/es, it is true, is to help the organism to float, and of the brushes to collect and direct particles of food. But in most cases a use has yet to be found for the hairs of Culicid larvae. But is it likely that every branch and every form of hair has an adaptive significance ? I think not. Given an organ that during evolution begins to vary in a definite direction, certain variations will be seized upon and adapted to definite uses. But it often seems that a process in evolution once started continues with an increasing momentum, and often cannot be checked ; and has
1 17
no relation to Natural Selection, except that it may
by hampering the organism. Such has almost certainly ha
in connection with the skeletal structures of variou
particularly in the matter of calcium carbonate secretion. In the
case of the larval hairs, it is possible that a tendency to branching,
flattening, and otherwise modifying the shape of a simple hair a
in primitive Culicid larvae; and as evolution proceeded this tend
gained in momentum in even- lineage, and has pi to the
extremes now met with in present-day Culicids. Where it could
put to a use this was done, as in the case of the float-hair- But oft n.
if not generally, when confronted with a Culicid larval h are
dealing, not with a complex adaptation, but with a variation which
has got out of hand possibly by the removal of some inhibiting
factor, which made for conservatism in an organ with great potential
variability.1
Before concluding, I would acknowledge, with many thanks, the ready assistance I have received from the following ; chiefly in the shape of material, particularly of various larval stages, but Ivice
and information. Without this help the handbook, imperfect as it is, would be vers- greatly impoverished : —
John Archibald, Esq., late R.A.M.C. ; R. F. Burton, Esq.; M L. E. Cheesman ; Dr. J. Davidson, late Capt. R.A.M.C : Dr. J. J. Day, late attd. R.A.M.C. ; Tickner Edwardes, Esq., late R.A.M M. Gross, Esq., late Capt. R.AAI.C. ; A. J. Grove, Esq., of the I. Government Board ; Col. S. P. James ; G. II. Lockett, Es . and the boys of Gresham's School, Holt; Major A. Macdonald, R.A.M Angus Macdonald, jnr. ; Major A. C. Parsons, R.A.M. C. : Mr. Ryan, late R.A.M.C. ; Dr. Hugh Scott'- ; D. J. So airfield. Esq. ; C. 1 Esq.; F. B. Taylor, Esq.; A. Vassall, Esq.; and my coll Major E. E. Austen, D.S.O. ; K G. Blair, Esq.; G. R Brook, ! late R.A.M.C. ; F. W. Edwards, Esq. ; and J. Waterst n, Es R.A.M.C.
1 C.Wesenberg-Lund (1919, \ idensk. Medd. fra 1 >ansk naturhisl I 1
accounts for the abundance and length of the larval hairs as at motions in the environment, but he does not aci
- By an oversight on p. 84, no acknowledgment to Dr. H presenting the Museum with specimens collected by him near Wareham.
1 [Q
INDEX OF THE TRIVIAL NAMES MENTIONED.
PAGE
affinis Stephens . . . . ioo albionensis MacGregor vi, 2*6-7, 109-11, ri2, 114, i-5 albofasciatus Macquart . . 8i albopunctatus Rondani . 96
alipes Theobald .... 109
annulatus Schrank vi, 24, 26, 29,
30, 32, 47, 70, 71, 74, 96> 98,
100-2, 106, 121-5
annulipes Meigen v, 35, 36, 38,
40, 42-3, 62, 63-6, 85-6, 87-8,
114, 122, 124
apicaliS Adams vi, 45, 46, 7--
106, 108-9, 113, 123, l25
bicolor Stephens (1 Meigen) . 105
bifurcatUS Linnaeus v, vii, 6, 32,
33-4, 35> 5°>5'-4 57-8, 73-5,
76-7, 78, 9°, io5> I22~3>
Plate II.
caJopus Stephens {non Meigen) 100 can tans Meigen .... 86-8
caspius Pallas v, vii, 24, 26, 28-9,
35, J^> 37, 38, 41, 43, 49- 59,
60-1, 62-7,81-4, 86, 89,96 7.
109, 112-3, 121-2, 124,
Plate IV.
ciliaris Linnaeus .... 79
cinereus Meigen v, 7, 17, 21,22, 23, 28, 47, 58,79-81, 114,121,
i-3 concinnus Stephens ... 91 confinnis Arribdlzaga ... <»s confirmatus Arribalzaga . . 8i
eurriei Coquillett v, 35, 37, \\,
62, 65-6, 82, 84 5. in. 114
detritus Hali. lay v, 35, 37,39,
4/, 4: \. 59 '"■ 65 '■• 69* 86. 89 90. 91 2, 97, 1 14, '-1-'-
1-4 diversus Theobald ... 94
doliorum Edwards . . 79i 108 domesticus Stephens, partim
(non Germar) . . • • 91
domesticus Stephens, partim
(and probably Germar) . 106 dorsalis Meigen ....
dugesi Dyar & Knab . . 10 1
dyari Coquillett . . . • 102
equinus Linnaeus . . . . 105
fasciatus Fabricius 10, 27, 51, 109-1 11, 112, 11; t'asciolatus Arribdlzaga fatigans Weidemann . . -i°7 : fenestralis Scopoli . . 5, 121
fumipennis Stephens \ i, 32. 44 r. 72, 100-3, 104 5. 1 11. 123
fusculiis Zetterstedt . .
fuscus Osten Sacken . . :<>. 80
g-eniculatus < Hivier vi, - 26. 28, 17, 39, 43i ■ 69, 70. 78, 91, 95 8. 109
112, II". 122, 124
mttatus Curtis ''''
■
hortensis Fi< albi • kochi Donitz . . ■ • lateralis Mi igen . leucopygus Eysell . lutcovittata Theobald ... "4 lutescens Fabricius . ' ' '
lutescens Stephen •• I >ri- cius). ...... ,o0
maccrai Dyar >v Knab
macula tits Me
I 20
maculipennis Meigen
28,
PAGE
v, vii, 5, 33-4, 35, 5°,
22, 24,
51-6, 57-8, 73-6, 77-8, 99-
101, 106, 1 2 1-3, Plate I.
marginalis Stephens . . . 106
morsitans Theobald vi, 25, 29-30,
32, 44-5, 4-, 71, 100-1, 102-4,
114, 121-3
nemoroSUS Meigen v, vii, ir, 15,
35, 37, 39, 4°, 4i, 42-3, 62, 63-4, 65, 67, 86, 89, 91-3, 94, 96-7, 106, 116, 121-2, 124 nigripes Staeger .... 78 nigripes Zetterstedt ... 91 nigrittilus Theobald . . 79, 108 nigritulus Zetterstedt . . 79, 108 onondagensis Felt ... 82 ornatus Stephens {non Meigen)
94, 96
81
113
penicillaris Rondani .
petrifactellus Cockerell
pipiens Linnaeus vi, 3, 4, 10. 22,
-V, 29, 45, 46, 48, 70, 72-3,
79, 91, 93, 96, ioi, 105-8,
114, 1 2 1-3, 125
pllimbeus Stephens v, vii, 32,
33-4, 35, 5°, 5*-6* 57-8, 68,
74, 76, 78-9, 96-8, 101, 109,
116, 122-4, Plate III.
plumosus Linnaeus . . 4, 121
poicilia Theobald .... 95
pPOtOlepis Cockerell . .113
protorhinus Cockerell . .113
pulchripalpis Rondani 83, 109, no
pulchripalpis Theobald 81, 109, 112
PAGE
pulicaris Linnaeus. . . . 105 punctatus Meigen .... Si pinutatus Stephens {non
Meigen) 106
ptmgens Robineau-Desvoidy . 94 pyrenaicus Brolemann . . .108-9 quadratimaculatus Macquart . 94 regelationis Linnaeus . . .^,121 reptans Linnaeus .... 105
richiardii Ficalbi vi, 24, 26, 30,
47- 98-100, 114, 1 2 1-3
rufus Gimmerthal . . .79,80
riifus Stephens {non Meigen). 106
rusticus Rossi v, 25, 27, 35, 37,
39, 4i-3, 48-9, 59, 62, 65, 67,
S5-6, 91, 94-5, 114, 122, 124
. . 89
• • i°5 . . 91 . . 91
salinus Ficalbi stercoreus Linnaeus sylvae Theobald . sylvaticus Meigen . sylvaticus Stephens
Meigen). sylvestris Theobald taeniorh xncJuts Arribalzasa
{non Wiedemann) .
terriei Theobald .
thcobaldi de Meijere .
titillans Walker
variegatus Schrank
vexans Meigen v, 35, 36, 37, 38,
40, 4^-3, 59, 6l> 65~6, 85, 86,
94, 114, 122, 124
waterhousei Theobald v, 35, 36,
37, 38, 4°, 42-3, 6*t ^2-6, 85,
86-7, 88, 114, 122, 124
{11011
106 59, 61, S5
98
89, 90 104
98 87
I 2 I
LIST OF FIGURES.
i. Culex pipiens Linnaeus. Wing, to show nomenclature of veil _•. Chironomus plumosus (Linnaeus). Wing.
3. Trichocera regelationis (Linnaeus). Wing.
4. J? hyp hus fenes trail's Scopoli. Wing.
5. Aedes cinereus Meigen. Pupa.
6. Diagram of mosquito, to show the nomenclature of the pans.
7. Anopheles maculipennis Meigen. Diagram of larval head to show 1
distribution of hairs.
8. Theobaldia annulata (Schrank). Diagram of larval head to show
distribution of hairs.
9. OcJikrotatus nemorosus (Meigen). Diagram of larval head t<
distribution of hairs.
10. Anopheles maculipennis Meigen. Diagram of larva to sh
nomenclature of parts.
11. A'edes cinereus Meigen. Diagram of larva to show the nomenclat
parts.
12. Anopheles maculipennis Meigen. Diagram of und< i side of larval 1
show nomenclature of parts.
13. A edes cinereus Meigen. Antenna of male.
14. A edes cinerais Meigen. Antenna of female.
15. Anopheles maculipennis Meigen. Abdomen ol male.
16. Culex pipiens Linnaeus. Abdomen of female
17. Acdes cinereus Meigen. Profile of the head of male.
18. Anopheles maculipennis Meigen. Palp 0!' male, from aboA
19. Culex pipiens Linnaeus. Palp of male, from the si
20. Ochlerotatus caspius (Pallas). Palp of male, from abo
21. Theobaldia annulata (Schrank). Palp of male, from aboi
22. Culex pipiens Linnaeus. Scutellum.
23. Culicclla morsitans (Theobald). Genitalia of male.
24. Taeniorhynchus richiardii (Ficalbi). Hind iale.
25. Ochlerotatus caspius (Pallas). Claws ale.
26. Taeniorhynchus richiardii (Ficalbi). Claw
27. Anppheles maculipennis Meigen. H female, from a
28. Ochlerotatus caspius (Pallas). Headoffemal ive.
29. A'edes cinereus Meigen. Head of female, bom ah-
122
30. Ochlerotatus caspius (Pallas). Claws of fore-leg of female.
31. Culicella morsitans (Theobald). Claws of fore-leg of female.
32. Culex pipiens Linnaeus. Hind-leg of female.
33. Theobaldia annulata (Schrank). Venation of distal part of wing.
34. Culicella morsitans (Theobald). Parts of 3rd, 4th and 5th longitudinal
veins to show relative positions of cross-veins.
35. Taeniorhynchus richiardii (Ficalbi). Parts of 3rd, 4th and 5th longitudinal
veins to show relative positions of cross-veins.
36. Theobaldia annulata (Schrank). Second abdominal segment, from above.
37. Culicella morsitans (Theobald). Second abdominal segment, from above.
38. Taeniorhynchus richiardii (Ficalbi). Piece of the third longitudinal vein to
show the broad scales.
39. Culicella morsitans (Theobald). Piece of the third longitudinal vein to
show the narrow scales.
40. Anopheles maculipennis Meigen. Scale-tuft on anterior part of thorax.
41. A. bifurcatus (Linnaeus). Scale-tuft on anterior part of thorax.
42. A. bifurcatus (Linnaeus). Scutellum.
43. A. plumbeus Stephens. Scutellum.
44. A. maculipennis Meigen. Side-piece and clasper of genitalia of male.
45. A. bifurcatus (Linnaeus). Side-piece and clasper of genitalia of male.
46. A. plumbeus Stephens. Side-piece and clasper of genitalia of male.
47. Ochlentalus caspius (Pallas). Right hind-leg.
48. O. vcxans (Meigen). Right hind-leg.
49. 0. waterhousei (Theobald). Right hind-leg.
50. O. annulipes (Meigen). Right hinddeg.
51. O. caspius (Pallas). Abdomen of female, from above.
52. O. vcxans (Meigen). Abdomen of female, from above.
53. 0. waterhousei (Theobald). Abdomen of female, from above.
54. O. annulipes (Meigen). Abdomen of female, from above.
55. O. detritus (Haliday). Abdomen of female, from above.
56. 0. ncmorosus (Meigen). Abdomen of female, from above.
57. 0. rusticus (Rossi). Abdomen of female, from above.
58. Finlaya geniculata (Olivier). Abdomen of female, from above.
59. Ochlerotatus caspius (Pallas). Genitalia of male.
60. O. vcxans (Meigen). Genitalia of male.
61. O. -ivatcrhousei (Theobald). Genitalia of male.
62. O. annulipes (Meigen). Genitalia of male.
63. O. detritus (Haliday). Genitalia of male.
64. O. ncmorosus (Meigen). Genitalia of male.
65. O. rusticus (Rossi). Genitalia of male.
66. Finlaya geniculata (Olivier). Genitalia of male.
67. Ochlerotatus detritus (Haliday). Scales on fork of second longitudinal
vein.
68. 0. ncmorosus (Meigen). Scales on fork of second longitudinal vein.
123
69. Culicella morsitans (Theobald). Proboscis of fem
70. C.fumipennis (Stephens). Proboscis of female.
71. C. morsitans (Theobald). Sixth abdominal segment of m >ro
beneath.
72. C. fumipennis (Stephens;. Sixth abdominal segment of male, from
beneath.
73. Culex apicalis Adams. Sixth abdominal segment of female, from ai
74. Taeniorhynchus richiardii (Ficalbi). Siphon and comb-scale of Ian
75. Aides cinereus Meigen. Siphon, pecten-tooth and comb-scale of larva.
76. Thcobaldia annulata (Schrank). Siphon, pecten-tooth and comb-s<
larva.
77. Culicella morsitans (Theobald). Siphon, pecten-tooth and comb-scale of
larva.
78. C. fumipennis (Stephens). Siphon, pecten-tooth and comb-scale
larva.
79. Culex pipiens Linnaeus. Siphon, pecten-tooth and comb-scale of larva.
80. Anopheles maculipennis Meigen. Head of fourth larval instar. Si. A. bifurcatus (Linnaeus). Head of fourth larval instar.
82. A.plumbeus Stephens. Head of fourth larval instar.
83. A. maculipennis Meigen. Comb of fourth larval instar.
84. A. bifurcatus (Linnaeus). Comb of fouth larval instar.
85. A.plumbeus Stephens. Comb of fourth larval instar.
86. A. maculipennis Meigen. Head of third larval instar.
87. A. bifurcatus (Linnaeus). Head of third larval instar. •88. A. plumbcus Stephens. Head of third larval instar.
89. A. maculipennis Meigen. Comb of third larval instar.
90. A. bifurcatus (Linnaeus). Comb of third larval instar.
91. A.plumbeus Stephens. Comb of third larval instar.
92. A. maculipennis Meigen. Head of second larval instar.
93. A. bifurcatus (Linnaeus). Head of second larval instar.
94. A.plumbeus Stephens. Head of second larval instar.
95. A. maculipennis Meigen. Comb of second larval instar.
96. A. bifurcatus (Linnaeus). Comb of second larval instar.
97. A.plumbeus Stephens. Comb of second larval instar.
98. A. maculipennis Meigen. Head of first larval instar.
99. A. bifurcatus (Linnaeus). Head of first larval instar. 99a. A. plumbcus Stephens. Head of first larval instar.
100. A. maculipennis Meigen. Combs of first larval instar.
101. A. bifurcatus (Linnaeus). Combs of first larval instar. 101a. A.plumbeus Stephens. Combs of first larval instar.
102. A. maculipennis Meigen. Tuft of bristles on ventral sui ninth
abdominal segment of first larval instar.
103. A. bifurcatus (Linnaeus). Tuft of bristles on ventral surl I ninth
abdominal segment of first larval instar.
I24
103a. A. plumbeus Stephens. Tuft of bristles on ventral surface of ninth abdominal segment of first larval instar.
104. Finlaya geniculate. (Olivier). Antenna of fourth larval instar.
105. Ochkrotatus caspius (Pallas). Siphon, pecten-teeth and comb-scale of
fourth larval instar.
106. O. caspius (I 'alias). Siphon, pecten-teeth and comb-scale of third larval
instar.
107. O. caspius (Pallas). Siphon, pecten-teeth and comb-scale of second
larval instar. 10S. O. caspius (Pallas). Siphon, pecten-teeth and comb-scale of first larval
instar. 109. 0. vexans (Meigen). Siphon of fourth larval instar (from fig. of Aedes
sylvestris in Dyar, Howard and Knab). no. O. wat'erhousei (Theobald). Siphon, pecten-teeth and comb-scale of
fourth larval instar. in. O. annulipes f Meigen). Siphon, pecten-teeth and comb-scale of fourth
larval instar.
112. 0. rusticus (Rossi). Siphon, pecten-teeth and comb-scale of fourth
larval instar.
113. 0. nemorosus (Meigen). Siphon, pecten-teeth and comb-scale of fourth
larval instar.
114. O. nemorosus (Meigen). Siphon, pecten-teeth and comb-scale of third
larval instar.
115. O. nemorosus (Meigen). Siphon, pecten-teeth and comb-scale of second
larval instar.
116. O. nemorosus (Meigen). Siphon, pecten-teeth and comb-scale of first
larval instar.
117. Finlaya geniculata (Olivier). Siphon, pecten-teeth and comb-scale of
fourth larval instar.
118. F. geniculata (Olivier). Siphon, pecten-teeth and comb-scale of third
larval instar.
119. F. geniculata (Olivier). Siphon, pecten-teeth and comb-scale of second
larval instar.
120. F. geniculata (Olivier). Siphon, pecten-tooth and comb-scale of first
larval instar.
121. Ochkrotatus detritus (Haliday). Siphon, pecten-teeth and comb-scale of
fourth larval instar.
122. O. detritus (Haliday). Siphon, pecten-teeth and comb-scale of third
larval instar.
123. Theobaldia annulata (Schrank). Siphon, pecten-tooth and comb-scale
of third larval instar.
124. T, annulata (Schrank). Siphon, pecten-tooth and comb-scale of second
larval instar.
125. T. annulaia (Schrank). Siphon, pecten-tooth an<l i
larval instar.
126. Culex pipiens Linnaeus. Siphon, 1
larval instar.
127. C. pipiens Linnaeus. Siphon, pecten-tooth and •
larval instar.
128. C. pipiens Linnaeus. Siphon, pecten-tooth and comb-
instar.
129. C. apicalis Adams. Siphon, pecten-tooth and comb I >arth
larval instar.
130. Orthopodomyia albionensis MacGregor. Headoffemal
131. Orthopodomyia albionensis MacGregor. Fore-tai female.
132. Orthopodomyia albionensis MacGregor. Siphon and comb-scali
fourth larval instar.
An< ipheles maculipi i i
i
Anopheles bifurcatu
PLAT
Anopheles plumbeus Stephens. Fern
4
Ochlerotatus caspius I Pall i I
Ochlerotatus nemorosus (Meigen). I
QL
536
B68
& r
British Museum (Natural History) Dept. of B
A handbook of Britisl mosquitoes
PLEASE DO NOT REMOVE CARDS OR SLIPS FROM THIS POCKET
UNIVERSITY OF TORONTO LIBRARY
•
*S
I
k?
:
I
L Jf
t P '
|
% |
|
B ^^B ^Hl ^^H ^^M |
1 , 1 |
i
:
i «*
I