_Key to Genera._
_a._ Eye developed.
_a^1._ No comb on head.
_a^2._ Pygidium not projecting backwards; frons
with tubercle _Ceratophyllus_.
_b^2._ Pygidium strongly convex, projecting
backwards; frons without tubercle _Pygiopsylla_.
_b^1._ Two spines at angle of genæ _Chiastopsylla_.
_b._ Eye vestigial or absent.
_a^1._ Abdomen without comb.
_a^2._ Hind edge of tibiæ with about eight short
and several long bristles, which do not form
a comb.
_a^3._ Fifth segment in fore and mid tarsi with
five, and in hind tarsus with four bristles _Neopsylla_.
_b^3._ Fifth segment in fore and mid tarsi with
four, and in hind tarsus with three lateral
bristles, there being an additional pair of
bristles in all the tarsi on the ventral
surface in between the first pair _Ctenophthalmus_.
_b^2._ Hind edge of tibiæ with about twelve short
and three long bristles, the short ones forming
a kind of comb _Ctenopsylla_.
_b^1._ Abdomen with at least one comb _Hystricopsylla_.
Genus. *Pulex*, Linn.
*Pulex irritans*, L., 1758.
Male 2 to 2·5 mm. in length, females about 4 mm.; reddish or dark
brown; head without bristles; thoracic and abdominal rings of bristles
on the dorsal aspect, and small hairs directed backwards at the
posterior margin. The barrel-shaped white eggs are deposited in cracks
in the boards, sweepings, spittoons, etc.; they produce legless larvæ
consisting of fourteen segments, which, after about eleven days, are
transformed into pupæ; after another eleven days the flea emerges.
[Illustration: FIG. 382.--_Pulex irritans._ 14/1.]
[Illustration: FIG. 383.--Larva of flea. Enlarged. (After Railliet.)]
[Illustration: FIG. 384.--_Pulex serraticeps._ 22/1.]
Fleas live in human dwellings all over the world, and periodically
pass on to persons to suck their blood. They may deposit their
eggs on very uncleanly individuals, and even undergo development,
therefore it is possible to find larvæ and pupæ on such persons.
The dog flea, _Pulex serraticeps_, is easily distinguished from the
flea of man by the large thick bristles on the posterior margin of
the first thoracic ring (fig. 384).
Genus. *Xenopsylla*, Glink.
*Xenopsylla cheopis*, Rothschild.
This is the common rat flea of tropical countries. Rothschild[377]
says: “Although practically cosmopolitan, it cannot apparently flourish
in temperate and cold climates.”
[377] _Bull. Ent. Res._, 1911, i, pt. 2, p. 92.
In the male the bristles of the flap-like process of the clasper all
slender; in the female the narrow portion of the receptaculum seminis
long. Originally discovered in Egypt.
This is apparently the chief plague flea. The Indian Plague Committee
have proved that this flea is easily infected when fed on plague rats,
and that the bacillus multiplies rapidly in the flea’s stomach and
that the fleas may remain infective for fifteen days. How the flea
infects man does not apparently seem to have been proved, as it does
not do so through its bite, but the excrement is highly infective. It
is probable that this poisoned fæcal matter gets to the wound caused by
the piercing mouth.
*Xenopsylla brasiliensis*, Baker,
occurs on rats in West Africa and has been introduced into Brazil.
Genus. *Ctenocephalus*, Kolen.
Includes the cat and dog fleas. The dog flea, _C. canis_, Dugès, is
found on the dog all over the world, but especially in temperate
climates. It also occurs on rats. Man is often badly bitten by this
insect and it overruns houses. The eggs are laid on rugs, carpets and
dust and dirt and amongst dogs’ hair, but are not fastened to it and
fall anywhere. The ova may hatch in about fifty hours and the larvæ
live for seven days and then spin their cocoons amongst dust and dirt.
The pupal stage lasts about eight days.
The cat flea (_C. felis_) is widely distributed over the world, and
occurs on many mammals beyond the cat, and is also found on rats.
Genus. *Hoplopsyllus*, Baker.
A genus found in North America related to Pulex, but at once recognized
by the prothorax bearing a comb.
*Hoplopsyllus anomalus*, Baker,
which is found on the ground squirrel (_Citellus beecheyi_) in
California, and according to Rothschild once found on the rat, has been
proved to carry the plague bacillus and to play an important part in
plague infection in California.[378]
[378] “Report United States Public Health, 1909,” xxiv, No. 29.
Genus. *Ceratophyllus*, Centis.
*Ceratophyllus fasciatus*, Bosc.
This flea is also found on the rat in Europe and will attack man. It is
a plague carrier. It has eighteen to twenty teeth on the prothoracic
comb and no black spines on the head. The genus Ceratophyllus of Centis
has a pronotal comb and three ante-pygidial chætæ on each side. Two
other specimens recorded: _C. londiniensis_, Rothsch., and _C. anisus_,
Rothsch. The former on rats and mice in London, the latter on _Felis_
sp. from Japan and _Mus norvegicus_ in California.
Genus. *Ctenopsylla*, Kolen.
This genus contains a very abundant rat and mouse species, _C.
musculi_, Dugès, which is widely distributed over the globe.
Genus. *Hystrichopsylla*, Tasch.
Large hairy fleas, with no eyes and one or more combs on the abdomen.
In the Mediterranean area one species, _H. tripectinata_, Tirah, is
common on rats and mice, and also in the Azores. Several others occur
on rats and mice. For information concerning these the reader is
referred to Rothschild’s papers.
*Pulex pallipes* is another species found on the rat and man.
*Systematic, Anatomical, and Biological Remarks on Mosquitoes.*
Mosquitoes come in the _Nematocera_, one of the sub-orders of the
_Diptera_, and are divided into numerous families, of which, however,
the _Culicidæ_ are of most interest to us here. Other families as the
_Psychodidæ_ and _Chironomidæ_ are also of considerable importance,
_vide_ following pages. The head is small, the facetted eyes are
placed laterally, but there are no accessory eyes (ocelli). In
front of the eyes are situated the comparatively long antennæ, the
differences of which strongly mark the distinction of sex.[379]
[379] [This is by no means always the case; in the genera Deinocerites,
Wyeomyia, Limatus, Theobald, and in Sabethes, Robineau Desvoidy, they
are nearly the same in both sexes.--F. V. T.]
The antennæ are composed of fifteen or sixteen segments. In the male
they are covered with long whorl-like hairs, while in the female the
antennal hairs are short--differences that are perceptible even with
the naked eye.[380] The proboscis, which is longer than the antennæ,
protrudes from the inferior aspect of the head and is composed of
the following parts (figs. 387 and 388): Two grooved half tubes,
facing one another, of which the upper one is the upper lip (labrum)
and the lower one the lower lip (labium), which represents a pair
of coalesced maxillæ. Within the tube formed by the labrum and
labium are the mandibles and maxillæ, transformed into instruments
for piercing, and a single puncturing organ, the hypopharynx. On
the right and left, next to the proboscis, are placed the straight
five-jointed palpi, the final joint of which is thickened in the
male.[381] In biting, the labrum, which is swollen at its free end,
is not introduced into the wound like the other mouth parts, but
is bent backwards. The labium and hypopharynx push direct into the
skin; the maxillæ and mandibles, however, which are needle-like
and serrated at the tips, penetrate with a saw-like movement. [The
swollen free end of the labrum really means the _labellæ_, two
articulated pieces, supposed by some to be the labial palpi. In most
species the mandibles are not serrated at their ends.--F. V. T.]
The saliva is introduced into the wound through the lumen of the
hypopharynx, while the blood is sucked up by the mosquito in the
groove of the labium.
[380] [This is not always the case, _vide_ previous note.--F. V. T.]
[381] [This is only so in Anophelina and in the genus Theobaldinella,
Neveu-Lemaire, Grabhamia, Theobald, Acartomyia, Theobald, etc. In true
Culex and many other genera the male palpi are pointed.--F. V. T.]
The three thoracic segments are soldered together. The central one
carries the membranous wings on the sides of the dorsal surface; the
posterior somite carries the small halteres (rudimentary posterior
wings). There are three pairs of long slender legs on the lower side.
[Illustration: FIG. 385.--Head of a male (_a_) and of a female (_b_)
Anopheles. Slightly enlarged. (After Giles.)]
[Illustration: FIG. 386.--Head of a male (_a_) and of a female (_b_)
Culex. (After Giles.)]
[Illustration: FIG. 387.--Mouth parts of _Anopheles claviger_.†
_h._, hypopharynx; _md._, mandible; _mx._, maxilla; _u.l._, upper lip;
_l.l._, lower lip; _p._, palpi. (After Grassi.)]
† [This should read _Anopheles maculipennis_, Meig.; there was no
type of _A. claviger_.--F. V. T.]
[Illustration: FIG. 388.--_Anopheles maculipennis_: transverse section
through the proboscis of a female (_a_) and a male (_b_). _hy._,
hypopharynx, with duct of the salivary gland; _m._, muscles; _md._,
mandibles; _mx._, maxillæ; _l._, labium; _l.l._, labrum. (After Nuttall
and Shipley.)]
The abdomen has no limbs, is composed of eight (rarely nine) distinct
segments; the sexual and anal orifices are at the posterior end, the
stigmata on the sides. The intestinal canal (fig. 389) is composed
of three principal divisions; the anterior part reaches as far as
the front pair of legs, and consists of the œsophagus, which is
provided with two small lateral diverticula. [At the commencement of
the œsophagus are one or more diverticula, which vary in size; they
contain air, food and bacteria.--F. V. T.] The mid gut reaches as
far as the fifth and sixth abdominal ring; in front it is thin, and
has numerous small supra-œsophageal ganglia; the posterior part is,
however, more dilated. Four or five Malpighian tubes, the excretory
organs, discharge at the place where the mid gut passes into the
terminal gut.
The pair of salivary glands have one common excretory duct leading
into the hypopharynx.
[Illustration: FIG. 389.--Longitudinal section of an Anopheles, showing
alimentary canal. In the forepart of the thorax is the salivary gland
consisting of three tubules; ventrally, the suctorial stomach extending
into the abdominal cavity; the stomach, and at the posterior end of the
abdomen the Malpighian vessels. (After Grassi.)]
These glandular bodies are situated in the thorax; each consists
of three slightly serpentine tubules, the dorsal and ventral tubes
being long, the central one shorter. The above-named characteristics
apply to both genera Culex and Anopheles, but in the genus Culex
is smaller, Anopheles larger. [In Anopheles the ends of the ducts
in the lobules are dilated, whilst in most of the genera the ducts
are the same size all along. The lobules may bifurcate, and in
Psorophora there are five lobules.--F. V. T.] The legs of the genus
Culex are about the same length as the whole body; in Anopheles they
are double that length.[382] In Anopheles the palpi and proboscis
are of equal length; in Culex the condition is different, according
to sex. In the male the palpi are longer than the proboscis; in the
female considerably shorter and the number of segments diminished.
The venation of the wings exhibits further points of differentiation,
as also their adornment, though this last sign is not by any means
always conclusive; most species of the genus Culex have unspotted
wings, whilst those of Anopheles are usually spotted. More important
is the fact that in Culex the abdomen is decorated with small scales,
similar to those on butterflies, whereas there are small bristles on
the abdomen of Anopheles. [This cannot be said to be a character by
which an Anopheline may be told from a Culicine, for in such common
Anopheline genera as Cellia and Neocellia we get plenty of scales
on the abdomen.--F. V. T.] An experienced observer can, however,
separate the two genera by the difference in size and their manner
of resting. When settled they either touch the resting place with
all the legs or only with the four anterior legs. In consequence
of the different length of the legs, the body of Culex approaches
the resting place more closely; moreover, Culex holds the abdomen
parallel or at an acute angle to the resting surface, whereas
Anopheles carries the abdomen directed upwards (at an angle of about
145°) and holds the head down. Both genera, however, usually only
rest on the four anterior legs, and then, as has long been known,
Culex carries the third pair directed towards the dorsum, while those
of Anopheles hang down.
[382] [This is certainly not always the case.--F. V. T.]
In regard to the differentiation of the species, I must refer you
to the special literature, and content myself by observing that
about 150 species of Culex and about fifty species of Anopheles have
been described, of which fifty about four are found in Europe.
[The number of known Anophelines now is more--100 species--of other
Culicidæ over 700.--F. V. T.] According to our present knowledge it
appears that the entire genus Anopheles can transmit malaria to man;
this observation has been confirmed in _Anopheles claviger_, Fabr.;
_A. maculipennis_, Meig.; _A. bifurcatus_, L.; _A. superpictus_,
Grassi; _A. pseudopictus_, Gr., all of which are found in Italy,[383]
Germany, etc., as well as in the tropics. Moreover, in _A. costalis_,
Loew; _A. funestus_, Giles (Africa); _A. quadrimaculatus_, Say (North
America), and _A. rossii_, Giles; the latter is perhaps identical
with _A. superpictus_, Gr., as well as with _A. culicifacies_
(India). [_Anopheles maculipennis_ and _A. claviger_ are the same.
Certainly neither _maculipennis_ nor _bifurcatus_ has been found
in the tropics. _Anopheles quadrimaculatus_, Say, is the same as
_A. maculipennis_. There is no evidence that _all_ Anophelines
carry malaria, but there is much to show that certain species
only are capable of so doing. A list of known carriers is given
later.--F. V. T.]
[383] Compare Ficalbi, E., “Venti spec. di zanzare (_Culicidæ_)
ital...,” _Bull. Soc. ent. ital._, 1899, xxxi; abstracted in
_Centralbl. f. Bakt., Par. u. Infektionsk._, 1900, xxviii, p. 397.
[Illustration: FIG. 390.--_Anopheles maculipennis_, Meigen. Enlarged.
(After Grassi.)]
Everyone is aware that mosquitoes swarm at sunset in fine weather,
and then seek out human beings and other warm-blooded animals to take
food. In this regard, however, the sexes differ, for it is almost
without exception that the females only suck blood, while the males
subsist on the juices of plants (blossoms or fruits).[384] After
sucking, and when night has fallen, the mosquitoes find a place of
refuge, for which purpose they utilize the grasses or foliage of
trees and bushes, or inhabited or uninhabited rooms of houses, also
cellars, stables, verandahs, etc., where they also pass the day.
[384] Both males and females may be kept alive in captivity for a long
time if given fruits, or even only sugar and water.
[Some mosquitoes bite in the daytime--Stegoymia and some Anophelines;
some bite right into the night, as _Culex fatigans_ and _C.
pipiens_.--F. V. T.]
The period required for digestion varies according to the
temperature. It takes two days in summer, and may take up to ten days
or more in cool weather. After digestion is complete more food is
taken up, this being necessary [in some species only--F. V. T.] for
the maturing of the sexual products in the female.
[Illustration: FIG. 391.--Larva of _Anopheles maculipennis_, Fabr.
Enlarged. (After Grassi.)]
[Illustration: FIG. 392.--Larva of Culex. Enlarged. (After Grassi.)]
It is still unknown under what circumstances copulation takes
place;[385] in any case, sooner or later the females are fecundated,
and when the ova have become mature, and the season is not too far
advanced, they seek a suitable place in which to deposit them.[386]
These are larger or smaller, permanent or temporary, collections of
standing water, pools, puddles, lakes, pits, water in rain-water
barrels, basins, etc. Nevertheless, certain kinds prefer certain
waters; thus _Anopheles_ (_claviger_) _maculipennis_ and several of
the Culices seek stagnant water overgrown with swamp vegetation and
decomposing vegetable matter; _A. bifurcatus_ and certain Culices,
clear water with some vegetation (such as fountains and the lakes in
gardens and parks); _Culex pipiens_ has a preference for rain-water
barrels, even though the water be dirty and evil-smelling. [I have
found the larvæ of _Anopheles bifurcatus_ living in great numbers in
ponds and lakes completely overgrown with floating water-weeds, and
those of _Culex pipiens_ in liquid manure.
[385] The act of copulation in many species is now known. The female
Culex has three receptaculæ seminalis, while the female Anopheles has
one receptaculum seminis.
[386] It is certain that the females perish immediately after
depositing the ova; but this does not always hold good, as a part of
them survive for a few days. The males die soon after copulation.
_Sexual Organs of the Mosquito._--The female has a pair of ovaries,
opening into a single tube by the ovarian tubes; into the single tube
opens a duct coming from the spermathecæ, and also a mucous gland.
The spermathecæ store up the male cells. The male organs consist of
two testes joined by ducts (vasa deferentia) to the ejaculatory duct
formed by their union. Each vas deferens is joined by a short tube
with the sac-like vesicula seminalis.--F. V. T.]
There is also a difference in the manner in which Culex and Anopheles
deposit their ova. Culex deposits two to three hundred eggs in
compact heaps that float on the water, and in which the eggs stand
perpendicularly one next the other; whereas _Anopheles maculipennis_
deposits only three or four up to twenty eggs, united in groups that
float horizontally on the water; the eggs of _A. bifurcatus_, again,
are arranged in star-like groups. The eggs are about 0·75 mm. in
length, and assume a dark hue soon after being laid. The development
only occupies a few days. The young larvæ grow rapidly, changing
their integument several times; the larvæ also differ in the various
genera, though they have a general resemblance (figs. 391 and 392).
The long legless larva has a flattened head, a fairly broad,
rectangular, or trapeziform thorax, on which there are bristles, and
an abdomen distinctly segmented, and on the segments of which there
are also lateral bristles. The situation of the stigmata marks the
difference between the two genera. Though in both genera the stigmata
are at the posterior end and on the dorsal surface, they are in
Anopheles close to the surface of the body; in Culex, however, they
are on the free end of a long tube (siphon).
[Illustration: FIG. 393.--Pupa of _Anopheles maculipennis_, Meig.
Enlarged. (After Grassi.)]
The position of the larva in the water also differs. The larva of
Anopheles lies almost horizontally beneath the surface of the water,
the posterior border of the penultimate abdominal segment, upon which
the stigmata are situated, being on the surface; whereas the larva of
Culex hangs head downwards perpendicularly in the water, the point of
the siphon only touching the surface.
In about a fortnight the larva is fully grown and becomes a pupa.
The pupa (fig. 393), which moves in jerky movements, remains in the
water, but partakes of no food. In shape it somewhat resembles a
tadpole, that is to say, it consists of a bulky anterior portion, on
the surface of which the head, with its appendages, is recognizable,
and a more slender segmented abdomen. Above, on the thorax, there are
two small trumpet-shaped breathing tubes for the conveyance of air to
the tracheal system. After three or four days the perfect mosquito
hatches out, remains a short time on the surface of the water until
its chitinous integument is hardened, and then flies away.
The females that are fertilized in the autumn hibernate in sheltered
spots in the open air, or in houses, cellars, under stairs, in
stables, barns, etc., and are the progenitors of the first generation
of the following year.
In accordance with the climate of a country, or the kind of weather
of a year, the conditions in regard to the manner of life and the
duration of the development of the mosquito vary. At all events,
the life-history of the mosquito elucidates many points relating to
malaria which were hitherto not understood.
[The length of the egg, larval and pupal life varies so much that it
is not possible to give an account of any value here. Frequently the
eggs may incubate in two days, whilst I have had _Stegomyia fasciata_
eggs from Cuba that have hatched out under abnormal circumstances
more than two months after they were laid (“Mono. Culicid.,” iii,
p. 6). Some larvæ, as _Anopheles bifurcatus_, live for months during
the winter. Some mosquitoes therefore hibernate as larvæ. The larvæ
and pupæ of the different genera present very marked characters,
mainly in regard to the structure of the siphons. Specific
differences may be found in the frontal hairs of Anopheline larvæ and
in the number and arrangement of a group of spines at the base of the
siphon in Culicines.--F. V. T.]
*Culicidæ or Mosquitoes.*
The importance of these insects to man is very great. They not only
produce painful bites, which may become inflamed and give rise to a
considerable amount of œdema, but they are more important on account
of the part they play in the distribution of various diseases.
_Culicidæ_ may not only carry disease germs, but act as intermediate
hosts for certain parasites, such as some of the _Anophelina_ for
malarial parasites, Culex for Filariæ, and Stegomyia for yellow
fever, etc.; the last-named is in any case the distributor of
that fatal disease. It is therefore very necessary to know the
life-history, habits and characters of these pests.
Mosquitoes exist in almost all parts of the world from the Arctic
circle to the tropics; temperate regions suffer from them less than
the two extremes, but even there they form not only a source of great
annoyance but of danger as malaria and possibly now and again yellow
fever carriers. A few years ago comparatively few species were known,
now some 800 odd have been described. Their number will probably not
stop far short of 1,000, in spite of the fact that many have been
described under different names, yet really the same species. Some
are purely domestic, others entirely sylvan; the former, as we might
expect, often have a very wide distribution, having been taken from
place to place in boats and trains. The more rapid transport becomes,
the greater becomes the possibility of this wide distribution of
many species increasing, and the spread of other species from their
natural home to foreign parts by sea and then by trains further
inland.
[Illustration: FIG. 394.--Heads of Culex and Anopheles: (1) Culex
male; (2) Culex female; (3) Anopheles male; (4) Anopheles female.
(After Daniels.)]
All _Culicidæ_ are aquatic in their larval and pupal stages. Almost
all small collections of water, both natural and artificial, may
form breeding grounds for these pests. Some even breed in pitcher
plants and many in bromelias. The favourite resorts for the larvæ
of Anophelina are small natural collections of water, such as
puddles, ditches and small pools around swamps; certain species (_A.
maculipennis_, etc.) live in rain barrels as well. They may also
occur in the sluggish water at the edges of rivers or even in mid
river, where the flow is checked by masses of water weeds (_Myzomyia
funesta_, etc.). The Stegomyias prefer artificial collections of
water, but also occur in natural pools. The yellow fever species
(_S. fasciata_) prefers small collections, such as in barrels, pots,
jars, etc. Culex occur in all manner of places--rain barrels, tanks,
cisterns, ponds and ditches. Some of the South American species of
Culex, Wyeomyia, Joblotia, etc., breed in the collections of water
at the base of bromelia leaves.[387] Very few Culicid larvæ live in
salt water except in Australia, where Dr. Bancroft has found them in
salt water of specific gravity 1·040 (_Mucidus alternans_ and _Culex
annulirostris_). Other salt water mosquitoes are known in America.
The food of the larvæ is very varied; the majority appear to feed
upon confervæ, small crustacea and insects; some are cannibals,
readily devouring others of their own kind. The larger larvæ of
Megarhinus, Psorophora, Toxorhynchites and Mucidus are extremely
ravenous and devour one another.
[387] “Wald Mosquitoes und Wald Malaria,” Dr. Lutz, _Centralbl. f.
Bakt., Par., u. Infektionsk._, i Abt. Orig., xxxiii, No. 4.
[Illustration: FIG. 395.--_a_, eggs of Culex; _b_^1 _b_^2, eggs of
Anopheles; _c_, egg of Stegomyia; _d_, egg of Tæniorhynchus; _e_, egg
of Psorophora.]
There are two main types of larvæ, the Anopheline and Culicine;
in the former there is no respiratory siphon, in the latter the
siphon is long or moderately long. The head offers certain marked
peculiarities which are of specific value; this especially applies
to the _Anophelina_, in which the frontal hairs are of great
service in distinguishing the larvæ,[388] whilst in Culex the
number and position of the spines at the base of and on the siphon
are characteristic. The position assumed by the larvæ in the water
also varies in the different groups; most of the Anophelines lie
horizontally, most of the _Culicina_ and _Ædeomyina_ hang head
downwards. The pupæ also vary, but not to the same extent; the chief
differences to be noticed are in the form of the two respiratory
trumpets.
[388] Information sent me by Dr. Grabham shows this statement to be not
quite correct, as the frontal hairs may vary in different stages of the
same larva. This he has shown in _Cellia albipes_, Theob., and I have
noticed it in a Nyssorhynchus from Africa.
[Illustration: FIG. 396.--Diagram showing the structure of a typical
mosquito. (Theobald.)]
The eggs, which may be laid separately (_Anopheles maculipennis_,
_Stegomyia fasciata_, _Joblotia nivipes_, etc.), or in rafts
(_Culex pipiens_, _C. fatigans_) or in chains (_Pseudotæniorhynchus
fasciolatus_), present a great variety of forms. The most peculiar
are shown in fig. 395 (Tæniorhynchus, Culex, Stegomyia, Anopheles,
Psorophora).
As in all insects, they differ very materially in each species of one
genus. Those best known are the Anopheline eggs.
The eggs always float on the surface of the water; immersion soon
destroys them, but many may occur in mud and can resist desiccation.
[Illustration: FIG. 397.--Types of scales, _a_ to _k_; head and
scutellar ornamentation, 1 to 5; forms of clypeus, 6. (Theobald.) 1,
head and scutellum of Stegomyia, etc.; 2, of Culex and Mansonia; 3, of
Howardina, Ædes, etc.; 4, of Megarhinus and Toxorhynchites, etc.; 5, of
Cellia and some other Anophelines; 6, _a_′, clypeus of Culex; _b_′ of
Stegomyia; _c_′, of Joblotia.]
_Characters of Adult Culicidæ._--The chief characters by which true
mosquitoes, or _Culicidæ,_ are known are the following:--
(1) Wings always with the veins covered with scales; the longitudinal
veins, usually six in number (in one genus seven); the costal vein
carried round the border of the wing.
(2) Head, thorax and abdomen usually, but not always (Anopheles,
etc.), covered with scales.
(3) Mouth parts formed into a long piercing proboscis.
As a rule the males may be told from the females by their antennæ
being plumose, whilst in the females they are pilose (_vide_
fig. 394), but this does not invariably hold good, for in
Deinocerites, Theobald, and Sabethes, Desvoidy, and others, they
are pilose in both sexes. The labial palpi are very variable in
regard to their form and the number of segments; in the _Anophelina_
they are long in both sexes, as long or nearly so as the proboscis,
more or less clubbed in the males; in _Culicina_, _Joblotina_ and
_Heptaphlebomyia_, they are long in the males, short in the females;
in _Ædeomyina_, short in both sexes.
[Illustration: FIG. 398.--Neuration of Wing. _Explanation of Wing,
Veins and Cells._--A, costal cell; B, sub-costal cell; C, marginal
cell; D, first sub-marginal cell (= first fork cell); E, second
sub-marginal cell; F, first posterior cell; G, second posterior cell (=
second fork cell); H, first basal cell; I, second basal cell; J, third
posterior cell; K, anal cell; L, auxiliary cell; M, spurious cell; _c_,
costal vein; 1_st_--6_th_, first to sixth longitudinal veins; _a_, _a_′
and _a_′′, incrassations (_a_′ called by Austen the sixth vein, _a_′′
the eighth vein); y, supernumerary cross vein; z, mid cross vein; _p_,
posterior cross vein; _s.c._, sub-costal. (Theobald.)]
_Scales_.--The most important structural peculiarities in _Culicidæ_
are the scales, which form the chief and most readily observed
characters for separating genera and species. The importance of scale
structure has been recently ignored by some workers, who are probably
right academically, but as a means of separating groups, and so more
easily running down a species, the practical man is strongly advised
to follow this method. As to what a genus is, is purely a matter
of personal opinion. If one examines any recent standard work on
entomology one will find a species being placed in varied genera by
the varied authorities.
The head, thorax, abdomen and wings are in nearly all cases clothed
with squamæ of varied form, of which the following are the main types
(fig. 397):--
(1) Flat, spade-shaped scales (_a_).
(2) Narrow curved scales (_e_).
(3) Hair-like curved scales (_d_).
(4) Spindle-shaped scales (_f_).
(5) Small spindle-shaped scales (_g_).
(6) Upright forked scales (_h_) and (_i_).
(7) Twisted upright scales (_j_).
(8) Inflated or pyriform scales (_k_).
(9) Mansonia scales (_b_).
(10) Small broad asymmetrical scales (_c_).
Various other varieties are found on the wings, such as:--
(1) Narrow linear lateral scales.
(2) Narrow lanceolate scales.
(3) Broad lanceolate scales.
(4) Elongated, broad, truncated scales (= Pseudotæniorhynchus-like
scales).
(5) Pyriform scales.
(6) Asymmetrical broad or Tæniorhynchus scales.
(7) Flat spade-like scales.[389]
[389] Heart-shaped scales occur on the wings of Etiorleptiomyia.
The wings have a series of scales along the middle line of the veins,
and also lateral scales to all or nearly all the veins. The wing
is also fringed by a series of scales (fig. 396), which, however,
are of little systematic importance; the so-called “border scales”
(b.s.) vary, however, to some extent, and are useful characters in
separating some of the Tæniorhynchus.
THE CLASSIFICATION OF _Culicidæ_.
SECTION A.--Proboscis formed for piercing; metanotum nude.
Scutellum simple.
I. Wings with six-scaled longitudinal veins.
A. Palpi long in the male.
α. Palpi long in both sexes, clavate in ♂ _Anophelina_.
I. First submarginal cell as long or longer than the second
posterior cell.
Antennal segments without dense lateral scale tufts.
{ {Wing scales
{ { lanceolate _Anopheles_, Meigen.
{ {Wing scales
{ { mostly long
{ { and narrow _Myzomyia_, Blanchard.
{Prothoracic {Wing scales
{ lobes { as above,
{ simple; no { but fourth
{ flat head { long vein
Thorax and { scales { near base
abdomen { { of third and _Neomyzomyia_, Theobald.
with hair- { { outstanding
like scales{ { scales on
{ { prothoracic
{ { lobe
{ {Wing scales
{ { partly large
{ { and inflated _Cycloleppteron_, Theobald.
{ Prothoracic lobes mammil-
{ lated; some flat head
{ scales. Basal lobe of ♂
{ genitalia of two segments _Stethomyia_, Theobald.
Prothoracic lobes with dense
outstanding scales _Feltinella_, Theobald.
Thorax with some narrow curved scales;
abdomen hairy _Pyretophorus_, Blanchard.
Wing scales small and lanceolate. Wing
scales broad and lanceolate _Myzorhynchella_, Theobald.
Thorax with hair-like curved scales,
some narrow curved ones in front;
abdomen with apical lateral scale
tufts, scaly venter; no ventral tuft _Arribalzagia_, Theobald.
Thorax with hair-like curved scales;
abdominal scales on venter only, with
a distinct ventral apical tuft _Myzorhynchus_, Blanchard.
Much as above, but abdomen with long
spine-like dense lateral tufts _Chrystia_, Theobald.
Thorax with very long hair-like curved
scales; abdomen pilose, except last
two segments which are scaly; dense
scale tufts on third femora; wings
with broadish, blunt, lanceolate
scales _Lophoscelomyia_, Theobald.
{Abdominal scales as
{ lateral dorsal patches
{ of small flat scales;
Thorax and { thoracic scales narrow
abdomen { and curved, or spindle-
{ shaped _Nyssorhynchus_, Blanchard.
with scales {Abdomen nearly completely
{ covered with irregular
{ scales and with lateral _Cellia_, Theobald.
{ tufts
{No lateral scale tufts _Neocellia_, Theobald.
Thoracic scales hair-like except a few
narrow curved ones in front; abdominal
scales long, broad and irregular _Kerteszia_, Theobald.
Thorax with hair-like curved scales and
some broad straight scales, others
spatulate on sides. Abdomen covered
with fine hairs except last three
segments, which are scaly. Tufts of
scales on hind femora. Wing scales
lanceolate _Manguinhosia_, Cruz.
Antennal segments with many dense scaly
tufts _Chagasia_, Cruz.
Antennæ with outstanding scales on
second segment, more appressed ones on
the first. At least one segment of
abdomen with long flat more or less
spatulate scales _Calvertina_, Ludlow.
II. First submarginal cell very small _Bironella_, Theobald.
With a distinct cylindrical tubercle
projecting obliquely from the
prothoracic region _Dactylomyia_, Newstead
and Carter.[390]
Scutellum trilobed.
First submarginal cell much smaller
than the second posterior cell;
proboscis long and bent _Megarhininæ._
Palpi long in both sexes _Megarhinus_, Rob. Desvoidy.
Last segment of ♂ palpi blunt. Last
segment of ♂ palpi long and pointed _Ankylorhynchus_, Lutz.
[390] The following genera of Anophelites have been founded by
James†:--
† _Records of Indian Museum_, 1910, iv, No. 5, p. 98.
(1) Abdomen with hairs but no scales. Thorax with dorsum with
long narrow curved scales, which form on the anterior promontory a
thick bunch projecting over the neck. Prothoracic lobes with a tuft
of rather broad true scales, upright forked scales of head of usual
broad expanding type: Patagiamyia, James. Includes Gigas, Giles, and
Lindesayi, Giles. Both seem to me typical Anopheles.
(2) Abdomen as above; Thorax very similar. Prothoracic lobes
with hairs, no scales. Upright forked scales of head rod-shaped:
Neostethopheles, James. Includes Atkenii, James; Immaculatus, Theobald;
Culiciformis, James and Liston. These seem to me to be true Anopheles.
(3) Abdomen with hairs and scales on dorsum of each segment; ventrally
there are six scaly tufts on the apices of six segments. Thorax
with scales and a tuft of outstanding ones on prothoracic lobes:
Christophersia, James. Type Halli, James. Very close to if not
identical with Cellia.
(4) Head with narrow curved scales lying rather flat upon head and
flat lateral scales, upright forked ones behind. Central lobe of
scutellum with tuft of narrow curved scales, lateral lobes with large
flat oval scales; male palpi longer than proboscis, two large apical
segments with long projecting hairs: Leslieomyia, Christophers. Type
_Leslieomyia tæniorhynchoides_, Christophers, from Amritsar, India.
(5) Abdomen with first six or seven segments with hairs only, eighth
and seventh (?) with scales, also genital processes. Thorax with hairs
and narrow curved scales sharp pointed, blunt-ended broad scales on
each side of anterior third. No tufts of scales on prothoracic lobes.
Head usual type of upright forked scales: Nyssomyzomyia, James. Type
Rossii, Giles.
β. Palpi short in the female _Toxorhynchites_, Theobald.
First submarginal cell longer than the
second posterior cell _Culicinæ._
Legs more or less densely scaly; head
not entirely clothed with flat scales;
all the legs densely scaly.
Wings with large pyriform scales _Janthinosoma_, Arribalzaga.
Head entirely clothed with flat scales.
Legs uniformly scaled with flat scales.
Head and scutellar scales all flat and
broad.
Palpi of ♀ short, of ♂ thickened
apically and tufted _Stegomyia_, Theobald.
Palpi of ♀ longer than in Stegomyia and
in ♂ long and thin, acuminate, simple _Desvoidea_, Blanchard.
Head scales mostly flat, but a median
line of narrow curved ones; scutellar
scales flat on mid lobe, narrow curved
on lateral lobes and palpi longer than
proboscis _Macleayia_, Theobald.
Head scales mostly flat, irregular,
narrow curved ones behind; mid lobe
scutellum with flat scales, lateral
with narrow curved; ♂ palpi shorter
than proboscis _Catageiomyia_, Theobald.
Head scales mostly flat, but a few
narrow curved ones in middle in front;
scutellar scales all flat _Scutomyia_, Theobald.
Head scales all flat; scutellar scales
all narrow curved _Skusea_, Theobald.
Head with flat scales, except a small
median area of narrow curved ones;
scutellar scales all narrow curved _Howardina_, Theobald.
Head with all flat scales except a thin
line of narrow curved ones behind;
scutellar scales all narrow curved _Danielsia_, Theobald.
Head with small flat scales over most
of surface, with median line and line
around eyes of narrow curved ones;
scutellar scales bluntly spindle or
club-shaped _Hulecoetomyia_, Theobald.
Head and scutellar scales narrow
curved.
Wing scales long, narrowly lanceolate,
collected in spots; palpi clubbed in
♂; five-jointed and rather long in ♀ _Theobaldia_, Neveu-Lemaire.
Wing scales (lateral) long and narrow,
and ♀ palpi three-jointed, ♂ not
clubbed and hairy _Culex_, Linnæus.
Wing scales at apex of veins dense and
rather broad, femora swollen; small
dark species _Melanoconion_, Theobald.
Wings with short, thick, median scales
and short, broadish lateral ones on
some of the veins; scales mottled;
fork-cells rather short _Grabhamia_, Theobald.
Wings with dense, broadish, elongated,
truncated scales _Pseudotæniorhynchus_, Theobald.
Wings with broad, short, asymmetrical
scales _Tæniorhynchus_, Arribalzaga.
Head covered with rather broad, flat,
spindle-shaped scales; scutellum with
small flat scales to mid lobe _Gilesia_, Theobald.
Head clothed with flat, irregularly
disposed scales all over, with patches
of narrow curved ones; ♂ palpi clubbed _Acartomyia_, Theobald.
Abdomen with projecting flat lateral
scales with deeply dentate apices;
wings not ornamented _Lasioconops_, Theobald.
Wings ornamented; scutellum with flat
and narrow curved scales _Finlaya_, Theobald.
γ. Palpi short in ♂ and ♀ _Ædeomyina._
Wings unornamented.
Antennæ pilose in ♂ and ♀; second joint
very long _Deinocerites_, Theobald.
Antennæ plumose in the ♂.
Head clothed with narrow curved and
flat scales.
Mid-lobe of scutellum with six border-
bristles.
Scutellum with narrow curved scales.
Palpi in ♀ four-jointed, in ♂ two-
jointed _Ædes_, Meigen.
Mid-lobe of scutellum with four border
bristles.
Scutellum with flat scales.
Head clothed with flat scales only.
Fork-cells normal length.
Mid-lobe of scutellum with four border-
bristles.
Palpi of ♀ two-jointed _Verallina_, Theobald.
Palpi of ♀ five-jointed, metallic _Hæmagogus_, Williston.
Fork cells very small or small.
Scutellar scales flat.
First submarginal cell longer than the
second posterior cell; no flat scales
on mesothorax _Ficalbia_, Theobald.
First submarginal cell smaller than the
second posterior cell; flat scales on
mesothorax _Uranotænia_, Arribalzaga.
Scutellar scales narrow curved.
First submarginal cell as in Uranotænia _Mimomyia_, Theobald.
Wings ornamented with Mansonia-like
scales _Ædeomyia_, Theobald.
SECTION B.--Metanotum ornamented with chætæ, squamæ or both.
α. With chætæ only.
Proboscis longer than whole body;
lateral wing scales Tæniorhynchus-like _Phoniomyia_, Theobald.
Proboscis as long as whole body in ♀ }
frons drawn out into a prominence; } _Binotia_, Blanchard =
wing scales rather broad and long } _Runchiomyia_, Theobald.
Proboscis not as long as the whole
body; lateral vein scales narrow _Wyeomyia_, Theobald.
Proboscis not as long as whole body,
swollen apically; wing scales long and
broad _Dendriomyia_, Theobald.
β. Metanotum with squamæ and chætæ.
Palpi short in ♂ and ♀.
Proboscis straight in ♀ and ♂; legs
with scaly paddles _Sabethes_, Rob. Desvoidy.
Venation like Sabethes.
Legs simple _Sabethoides_, Theobald.
Venation like Culex _Goeldia_, Theobald.
Proboscis in ♂ elbowed, with two scaly
tufts _Limatus_, Theobald.
Palpi long in ♂, short in ♀ _Joblotina_, Blanchard.
II. Wings with seven-scaled longitudinal
veins: Culex type _Heptaphlebomyia_, Theobald.