Samuel Wendell Williston.

Manual of North American Diptera online

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that of the posterior or great cross-vein (8) . . Triniicra.
The cross-vein situated near the end of the auxiliary vein (10) .



1. Discal cell open; antennae apparently 28-jointed in the ^ (28).

Discal cell closed. . . . . . . . . . 2

2. Marginal cross-vein wanting. .... Phyllolabis.
Marginal cross-vein present. ....... 3

3. Wings pubescent, . . . . . . Ulomorpha.

Wings bare. '4

4. Seventh vein very short, abruptly incurved toward the anal angle

(5) Trichocera.

Seventh vein not unusual. .5

5. A supernumerary cross-vein between the auxiliary vein and the

costa (p. 80, 5) Epiphragma.

No such supernumerary cross-vein (1, 9, 19) *. Limnophila.

* A wingless form has recently been referred to this genus, with
doubt, by Mr. Coquillett.



1. Three posterior cells; two submarginal cells (13) . Anisomera,
Four or five posterior cells; antennae of the $ sometimes much

elongated. .......... 2

2. The stigma occupies nearly the whole space between the tip of the

auxiliary vein and the marginal cross-vein, . Eriocera.

The stigma occupies but a small portion of the space between the
tip of the auxiliary vein and marginal cross-vein,



1. Antennae composed of thirteen joints ..... 2
Antennae composed of sixteen or seventeen joints, . . 5

2. Two cross-veins between the first longitudinal vein and the anterior

branch of the second vein, ..,,.., 3
Only one cross-vein between these veins. , . , , 4

3. Front with a gibbosity behind the antennae (2), . Dicranota,
Front without gibbosity Polyangaeus.

4. Five posterior cells; both branches of the fourth vein furcate (14) .

Rhaphidolabis .
Four posterior cells; the posterior branch furcate, Plectromyia,

5. Four posterior cells; wings pubescent. .... Ula,
Five posterior cells; wings bare, ...... 6

6. Anterior cross-vein nearly at right angles with the longitudinal axis

of the wing. ,,.....,, 7

Anterior cross-vein at a very oblique angle with the longitudinal

axis of the wing, and parallel with the posterior cross-vein

(p. 80, 1) Pedicia.

7. Rostrum much longer than the head. . . . Ornithodes.
Rostrum shorter than the head (4) . . . . Amalopis


1, Five posterior cells; colors yellow and black. Cylindrotoma,
Four posterior cells, ......... 2

2, Antennal joints .subcylindrical, elongated. .... 3
Antennal joints subglobular; head and thorax conspicuously punct-

ulate Triogma.

3, Colors yellow and black. ...... Liogma.

Colors brownish and grayish, .... Phalacrocera.



1. First subniarginal cell much shorter than the second. Idioplasta.
First subniarginal cell much longer than the second. . . 2

2. Three posterior cells (12) ..... Bittacomorpha.
Four posterior cells. . . . . . Ptychoptera.


1. Legs long and slender, especially the tarsi; anterior branch of the

second vein absent, obsolete or perpendicular, the rhomboid
cell more or less square. ....... 2

Legs not unusuallj^ slender, anterior branch of second vein present
and oblique. ......... 5

2. Antennae thirteen-jointed; male forceps complex. Dolichopeza.
Antennae with less than thirteen joints; male forceps small, simple. 3

3. Fifth posterior cell not in contact with discal cell. Megistocera.
Fifth posterior cell in contact with discal cell. ... 4

4. Head on a neck-like prolongation of the thorax; seventh vein short,

running into the anal angle. . . . Brachypremna.

Head more closely applied to the thorax; seventh vein terminates

in the margin at some distance from the anal angle. Tanyprema

5. Antennae of $ pectinate or sub-pectinate. .... 6
Antennae not pectinate. ........ 7

6. Ovipositor of 9 long) sword-like. . . . . Xiphura.
, Ovipositor of 9 lo"g but not sword-like (p. 80, 4) . Ctenophora.

7. Three posterior veins arising from the discal cell, the two anterior

sometimes arising together but the petiole always short (p. 80, 7)

Two posterior veins arise from the discal cell, the anterior one fur-
cate, petiole always of considerable length. ... 8

8. Antennae serrate; northern species. . . . Stygeropis.
Antennae not serrate below. ....... 9

9. Marginal vein wanting, but one marginal cell; antennal joints short

with minute bristles. ...... Holorusia.

Two marginal cells. ......... 10

10. Abdomen slender, very long; antennae composed of twelve joints.

Abdomen less elongate; antennae with thirteen joints (27).



Thickly haired, minute flies, in appearance moth-like.
Head small; ocelli wanting. Antennae as long as the
head and thorax together, bead-like; thickly haired;
composed of from twelve to sixteen joints; the two basal
joints shorter and short-cylindric. Proboscis usually
short ; or more or less elongated ( Ph lebotomus) and
rigid; palpi incurved and hairy; composed of four joints
of nearly equal length. Thorax not very convex, with-
out transverse suture; scutellum rounded. Abdomen
cylindrical, composed of from six to eight segments;
male genitalia prominent. Legs short, densely hairy;
claws small. Wings large, ovate or lanceolate in shape;
when at rest lying roof-like over the abdomen ; densely
covered with hair or tomentum, which also forms a fringe
around their margin; the costal vein continuous about
the wing; veins strong, for the most part concealed be-
neath the hair ; venation formed almost wholly by longi-
tudinal veins; the anterior cross-vein is short and lies
near the root of the wing and is often difficult of discern-
ment; the second longitudinal vein arises near the origin
of the first and is furcate. Fourth vein furcate; between
these two furcations there are usually two longitudinal
veins, the precise homologies of which are uncertain; the
front one is often supposed to be an additional furcation
of the second ; or it may be a furcation of the third occur-
ring before the anterior cross-vein, a peculiar structure
found elsewhere in diptera only among the Tipulidae
i^^Ptychopterince) . The vein just before the posterior furca-
tion terminates near the tip of the wing. Fifth and sixth
veins terminate in the border of the wing, as does also
the seventh, which is, sometimes, very short.




The members of this familj^ are often very minute,
rarely exceeding the length of four millimeters ; they are
observed in shady places, on windows, in outhouses, or
running about on leaves near streams of water, and will
be readily recognized by their peculiar moth-like appear-
ance ; they run about nimbly, but their flight is weak.
The larvae live in rotting vegetable material, in dung, or
in water; they are peculiar in having both open spira-
cles and tracheal gills ; the maxillae are imperfectly de-
veloped, there are eye-spots on the head, and the segments
behind the head are without feet, but are provided with
sucking disks, in the aquatic forms at least.

Fig. 26. Psychodidse. 1, Psychoda, W\v\g\ 2, Pericoma, ^Nxng
(Eaton); 3, Sycorax, wing (Eaton); 4, Trichoniyia, wing (Eaton).


1. Two simple longitudinal veins between the forked veins. . 2
One simple longitudinal vein between the forked veins. . 4

2. The first simple vein arises from the forked vein much beyond the

anterior cross-vein {Flebotonius!) . . Phlebotomus.
The first simple vein arises near anterior cross-vein. . . 3

3. The second simple vein ends at or near tip of wing (1) . Psychoda
The second simple vein ends distinctly beyond tip of wing (2).


4. The seventh longitudinal vein (the most posterior one) not much

shorter than the sixth (4) Trichomyia.

The seventh longitudinal vein very short (3) . . Sycorax.


III. Family DIXID^.

Fig. 27. Dixa species; enlarged. After Kellogg.

Rather small, slender, nearly bare species. Proboscis
somewhat projecting; palpi four-jointed; antennae long,
the basal joints thick, those of the flagellum hair-like,
and the joints indistinctly distinguishable. Eyes round,
dichoptic; no ocelli. Thorax strongly convex, without
transverse suture ; scutellum transverse ; metanotum
arched. Abdomen long and slender, composed of seven
or eight segments, thickened posteriorly in the male,
pointed in the female. Legs long and slender; coxae
somewhat elongated; tibiae without terminal spurs.
Wings comparatively large; auxiliary vein present, ter-
minating in the costa before the middle of the wing; the
second vein arises from the first near the middle of the
wing and appears to be the beginning of the third vein,
which continues its direction while the second arches
suddenly forward at or near the anterior cross-vein and
is furcate; fourth vein furcate; four posterior cells pres-




ent; the two basal cells complete; the anterior cross-
vein is near the beginning of the third vein, where the
second vein curves forward.

The family Dixidse comprises about a score of known
species belonging to the single genus Dixa. The genus
has been placed among the Tipulidse and Culicidae, but
is provisionally isolated into a separate family. The
larvae are aquatic, living in ponds or slowly running
water; they resemble those of the mosquitoes. The flies
are found in bushy, moist places about forests, and have
been observed by Winnertz dancing in the air in swarms.

IV. Family CUIvICID^.

Slender flies, for the most part characterized by the
projecting, slender proboscis and the thickly plumose
antennae of the males. Head small, subspherical; eyes
reniform; ocelli wanting. Antennae slender, elongate,
composed of fourteen or fifteen joints; first joint globose,
the following elongated, nearly or quite cylindrical and
beset with whorls of hair, forming, with but few excep-
tions, in the male a dense plumosity, but shorter and
less conspicuous in the female ; in the male the last two
joints almost always more elongated and nearly bare.
Thorax ovate, arched, but not projecting over the head,
without transverse suture; scutellum narrow, uni- or
trilobate; metanotum usually arched. Abdomen long
and narrow, somewhat flattened, composed of eight or
nine segments; male genitalia prominent; ovipositor
short. Legs long and slender; coxse not elongate ; tarsi
long; claws often denticulate, especially in the males.

Fig. 28. Venation of Culex.

Wings long and narrow, while at rest lying flat over
the abdomen; with six fully developed longitudinal
veins reaching the costal margin; the hind margin is



fringed with hair or scales and the costal vein encom-
passes the wing ; auxiliary vein distinct, reaching to or
beyond the middle of the wing; second, fourth and fifth
longitudinal veins furcate; third vein simple, arising
from the second angularly beyond the middle of the wing;
anterior cross-vein situated near or even proximal of the
origin of the third vein. Two basal cells present, elon-
gate, the anal cell wide open. Veins of the wings cloth-
ed with scales.

The foregoing description and figure of the wing do
not wholly agree with those of other writers. It is evi-
dent, unless we change the nomenclature of the brachy-
cerous flies, that the furcation of the second vein does
not form a submarginal cell; the so-called 'first submar-
ginal cell' is in reality the second marginal. Further-
more, it is as clearly apparent that the so-called 'poste-
rior cross-vein' is not the vein of that name among the
brachycerous and cyclorrhaphous flies, but is, rather, the
'discal' or 'discoidal cross-vein', or the 'anterior basal
cross-vein'; or, at least, a cross-vein which has not yet
received a definite name.

Since the last edition of this work was published, in
1896, the marvelous discoveries in the life histories of the
Culicidae, and their agency in the transfer of disease,
have given to the family an importance in man's econo-
my second to that of no other group of insects. Indeed,
one may say with entire truth that these little flies, or
'gnats' as the English call them, are the most baneful
and pestilential of all known insects. The microscopical
parasites producing malaria, yellow fever and filariasis
are now known with certainty to be transferred by the
agency of certain mosquitoes from one human being to
another, and it is probable, though of course not certain,
that if all the germ-bearing mosquitoes could be made
extinct these diseases would at least cease to trouble



Fig. 29. Mochlonyx cinctipes. Female adult; enlarged.
After J. B. Smith.



mankind. The parasitic microorganism is a small pro-
tozoan which undergoes development in the red corpus-
cles of the blood, destroying them, and there seems to be
no way, in general at least, in which it may be transfer-
red from one person to another save by the activity oi
these insects. Taken into the mosquito's stomach with
the blood sucked up by the insect it there undergoes
sexual regeneration, of which the newly generated germs
or 'blasts', penetrating the walls of the mosquito's stom-
ach, reach the salivary glands, and are thence transfer-
red with the poisonous saliva emitted by the insect into
the wounds made by its puncturing 'bites'.


Fig. 30. Ciilex- taeniorhynchus. i, female adult ; 2, front claws
of female; 3, front, 4 middle, 5, hind claws of male; all much enlarged.
After J. B. Smith.



Not all mosquitoes are criminals in this respect. Only
certain forms of Anopheles (in its wide sense) are known
to carry the germs of malaria ; while but a single species,



Fig. 31. Anopheles pu7ictipennis. i, female adult; 2, female pal-
pus; 3, genitalia; 4, part of wing vein showing scales; 5, front, 6,
middle claws of male; all much enlarged. After J. B. Smith.



the Ciilex or Stegomyia fasciata, is so far known to cause
the deadly yellow fever. But these disease-bearing spe-
cies are widely distributed over the earth, accounting
for the wide distribution of malaria and yellow fever.

Fig. 32. Aedes fusciis. 1, female adult; 2, female palpus; 3, male
palpus; 4, front, 5, middle, 6, hind claws of male; all much enlarged.
After J. B. Smith.


Probabh^ we shall yet learn of other mosquitoes which
are culprits in these respects.

This gravely important bearing of the mosquitoes in
man's economy has given a tremendous impulse to their
study, though not always with the most happy results so
far as their taxonomy is concerned. Whereas ten or
twelve years ago only about one hundred and fifty spe-
cies of the family were known, we now have an accred-
ited list of Culicidae of nearly or quite six hundred spe-
cies, and there are probably several hundred more yet
awaiting discovery.

It seems a fact that the mosquitoes present but few and
slight structural differences among themselves ; the many
closely related forms seem to indicate a late geological
crudescence. Such organisms are always difficult to
classify. The wing venation has acquired much fixity,
whereas the many secondar}^ sexual differences in the
mouth-organs would indicate a late adaptation to blood-
sucking habits. The Culicinae probably have developed
from the corethrine type, which is doubtless an older
type, now decidedly on the wane. Until within a few
years scarcely a half dozen genera of the mosquitoes had
been recognized by dipterologists, and they were based
chiefly on the secondary sexual mouth characters. Within
these few years, however, the numerous writers on this
group of insects have proposed fully one hundred gen-
era, for the most part merely subdivisions of the older
genera, founded on minor characters, chiefly the shape
and arrangement of the scales of the body and wings. It
seems to be the consensus of opinion among other dipter-
ologivSts that the use of such characters has been car-
ried to an undue and even absurd extreme. Of course
the first requisite in classification is that distinguishing
characters shall be 'natural', that is genetic, not homo-
plastic or parallel characters. When such are found it



really makes little difference how far they are carried,
save that their use in one group, necessitates or stimu-
lates the use of like minor characters in other groups.
One cannot raise a genus of Culicidse to family rank,
without raising all other genera of like degree pari passu.
But I am firmly of the opinion that the scale characters
are in a high degree artificial, and that their use will

Fig. 33. Aedes niusiciis. i, female adult; 3, claws of female front;
6, hind claws of male; enlarged. After J. B. Smith.



never be accepted by dipterologists in general. And
secondary sexual characters should also be tabooed so
far as possible, since they represent merely evolutional

The formation of so many genera from these slight
characters, is, however, no 'worse than the attempt to
classify and name genera and species purely from the
larval stage, which has been done to a degree never be-
fore attempted by scientific dipterologists.

Upon the whole the characters made use of in the fol-
lowing table, verbally modified from Dyar and Knab,
come nearest to my own views of proper classificatory
characters for the family. I am not able to test the table
thoroughly, and cannot vouch for it, but I believe it to
be the best that has so far appeared. The student may
also consult a recent table of the genera published by
D. W. Coquillett.*

The habits of the immature stages of the Culicidse are
so familiar to all that little need be said here regarding

The eggs are laid by the females upon the surface of
stagnant or nearly stagnant water, in groups or singly,
whence the young larvae, hatching, descend into the
water to form those active little creatures of the rain-
barrel, commonly known as 'wigglers'. The pupal stage
is less active, passed in large part near the surface of the
water, hanging by the respiratory tubes. The adult in-
sect emerges from the pupal skin through a rent, using
its discarded shell as a temporary raft until its wings
are fully extricated.

The following description of the larvae of the mosqui-
toes is paraphrased from Dyar and Knab:

* Bull. U. S. Dept. Agric. Tech. Ser. No. ii (1906).




Fig. 34. Psorophora ciliata. i, female adult; 2, female palpus; 3,
front; 4, hind claws of male; enlarged. After J. B. Smith.




Head well formed, enclosed in a chitinous covering;
with compound eyes, single-jointed antennse, a group of
liairs before tke oral orifice, toothed mandibles, maxillae,
and single-jointed palpi. Thoracic segments consolida-
ted into a transversely elliptical flattened mass ; abdomen
with nine slender and moniliform segments, the eighth
with a dorsal, respiratory opening, often prolonged into
a chitinous tube; last segment furnished with a chitin-
ous plate, and usually with four delicate anal append-
ages. The body has setae in tufts or singly, usually
more or less conspicuously feathered. From other aquatic
nematocerous larvae, the mosquitoes are distinguished
by the presence of the mouth-brush, the shape of the
anal segment and the absence of abdominal feet. The
larvae of Dixa and the Corethrinae are practicably indis-
tinguishable from those of the Culicinae, save by minor

I^'ig- 35' Culicidse. i, Megarhinus^ wing; 2, Megarhiniis, head,
male; 3, Aedes, wing; 4, Hcemagogus, head, female; 5, front claws
of Hcsniagogtis, male; 6, Wyeoniyia, head of female; 7, Corethra, hind

Proboscis short, not adapted for piercing. . . Corethrinae.
Proboscis much longer than the ^ head, firm, adapted for piercing.
Mosquitoes Culicinae.

*I especially commend to the student interested in this family of flies
the comprehensive and richly illustrated Report upon the Mosquitoes
of New Jersey (1904), by Prof. J. B. Smith,




1. Hind metatarsi shorter than the following joint {Corethra^ Coquil-

lett) . (fig. 29) Mochlonyx.

Hind metatarsi longer than the following joint. ... 2

2. Small species; ungues simple. ....'.. 3
Large species (10 mm); ungues bifid. . . . Pelorempis.

2. Antennae verticillate {Sayomyia Coq\x\\\&\X) (7). Corethra.

Antennae of male thickly clothed with long hairs; of the female

with a basal and an irregular median circlet of hairs on each

joint Corethrella,


1. Metanotum without setae (Culicini) . ..... 2

Metanotum with setae (Sabethini). ..... 15

2. vScutellum evenly rounded, not lobed. ..... 3

Scutellum distinctly trilobate. .....: 4

3. Second marginal cell longer than itspetiole (fig. 31) Anopheles.
Second marginal cell less than half as long as its petiole (1, 2).


4. Hind tibiae near their tip with a row of seven to twelve closely

set setae. .......... 5

Hind tibiae with none to five sparsely set setae. ... 14

5. Scutellum with its median lobe elongate, collar-like, not tubercu-

larly prominent, ......... 6

Scutellum with its median lobe distinctly prominent and tuber-
cular. ........... 7

6. Terminal antennal joints slender, long. . . Mansonia.
Terminal antennal joints short, broad. . . . Aedomyia.

7. Second joint of antennae very long, 14:1. . Deinocerites.
Second joint of antennae moderately long, less than 8;i. . 8

8. Second marginal cell less than half as long as its petiole.

Second marginal cell at least nearly as long as its petiole. 9

* My examination of the literature leads me to quite different con-
clusions than those of Coquillett regarding the types of Corethra and
Mochlofiyx. There is no call for disturbing these names so long es-


9. Head with a distinct neck, the occiput broad and exposed (fig. 34) .

Head without distinct neck, appressed to the thorax. . 10

10. Cross-veins approximated and nearly in line with the basal sec-

tion of the third vein. . . . - . Culiseta.

Cross-veins not approximated, separated by at least the length of

the posterior. ......... 11

11. Last segment of the female abdomen not extensile, large, trun-

cate; male genitalia with the harpes slender, columnar, with

bent, spined tip Tseniorhynchus.

Last segment of the fetiiale abdomen extensile, slender; male
genitalia with harpes broad, concavely curved. . . 12

12. Clypeus bare. ......... 13

Clypeus with dense appressed scales. . . . Stegomyia.

13. Prothoracic lobes approximated (4,5). . Haemagogus.
Prothoracic lobes well separated (figs. 32, 33). . Aedes.

14. Empodia large. Lutzia.

Empodia small (fig. 30) Oulex.

15. Clypeus M'ithout hairs. . . . . . . . .16

Clypeus hairy on the sides. ..... Joblotia.

16. Prothoracic lobes contiguous, densely hairy. . Sabethes.
Prothoracic lobes well separated. ...... 17

17. Eyes narrowly separated by the front; proboscis rather short,

swollen at tip. ......... 18

Eyes contiguous at vertex. . . . . •. . . 19

18. Hind tarsi with two claws, normal (6). . . Wyeomyia.
Hind tarsi with but a single claw. . . . Limatus.

19. No erect forked scales on occiput; proboscis longer than the body.


With a row of erect forked scales on occiput; proboscis not longer

than the body. . . . . . . . . . 20

20. Face normal, smooth. .... Lesticocampa.
Face with a conical process above the clypeus. Runchomyia.

The following synonymy is given by Dyar and Knab:

Anopheles Meigen: Myzotnyia Blanch., Cycloleppteron Theob:
Nototricha Coq., Cellia Theob., Arribalzagia Theob., Coelodiazesis
D. and K.

Mansonia Blanch.: Pneiimaculex Dyar.


Taeniorhynchus Lynch: Coquillettidia Dyar.

Aedes Meigen: Ochlerotatus J^ynch., Hetoronycha hynch.,Ja?Uhino-
sonia Lynch, Conchyliastes Coq., Grabhatnia Theob., Howardina
Theob., Culiselsa Felt, Ciilicada Felt, Ecculex Felt, Prolocu/est: Felt,
Pseudoculex Y)ya.r, Gyni7iornetopa Coq., Lepidoplatys Q.oq^., Feltidia
Dyar, Ceratocystia D. & K.

Hsemagogus Will.: Cacomyia Coq., Stegoconops 'L,\x\.z.

CulexLinn.: NeoculexTiyox, Culicella Felt, Melanoconion, Theob.,
Ttnolestes Coq. , Micrcsdes Coq. , Isostomyia Coq. , Mochlostyrax D.&K.

Sabethes R.-D. : Sabethoides Theob.

Wyeomyia Theob.: Dendroniyia T\\eoh.

Liraatus Theob.: Stniondella Laveran.

Joblotia Blanchard: Trichoprosopon Theob.


Gnatlike flies of slender form, seldom reaching ten mil-

Online LibrarySamuel Wendell WillistonManual of North American Diptera → online text (page 7 of 25)