Samuel Wendell Williston.

Manual of the families and genera of North American Diptera online

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Eirst submarginal cell more than half the length of the second. 10

7. Marginal cross-vein present 8

Marginal cross-vein absent. . . . Gokomyia Osten Sacken.

8. Second submarginal cell in contact with the discal cell, the anterior

cross-vein obsolete. ......... 9

Anterior cross-vein present, the first posterior cell intervening between
the submarginal and the discal cells. . Empeda Osten Sacken.

9. Anal cell closed; no empodia (Asia, Africa and West Indies).

MoNGOMA Westwood.
Anal cell open; empodia present (Central and South America).

Paratropesa Schiner.

10. Seventh longitudinal vein conspicuously bisinuate. Symplecta Meigen.
Seventh longitudinal vein straight. 11

11. Length of the auxiliary vein beyond the cross-vein at least twice that

of the posterior cross-vein. . . Trimicra Osten Sacken.

The cross-vein situated near the end of the auxiliary vein.

Gnophomyia Osten Sacken.



LIMNOPHILINI.

1. Discal cell open; antennae apparently 28-jointed in the $.

PoLYMERA Wiedemann.
Discal cell closed -2

2. Marginal cross- vein wanting. . . Phyllolabis Osten Sacken.
Marginal cross- vein present . • • 3

3. Wings pubescent Ulomorpha Osten Sacken.

Wings bare. .......•••• 4

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

Trichocera Meigen.
Seventh vein not unusual. .' . . . • • • • ^

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

Epiphragma Osten Sacken.
No such supernumerary cross-vein. . . Limnophila Macquart.



TIPULID^. 35

ANISOMERINI.

1, Three posterior cells; two submarginal cells. Anisomera Meigen.
Four or five posterior cells ; aiitennse of the $ sometimes much elon-
gated . . . . . .2

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

iliary vein and the marginal cross-vein. . . Eriocera Macquart.

The stigma occupies but a small portion of the space between the tip of

the auxiliary vein and marginal cross-vein. Penthoptera Schiner.

AMALOPINI.

1. Antennae composed of thirteen joints 2

Antennae composed of sixteen or seventeen joints. ... 4

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

branch of the second vein. , . . Dicranota Zetterstedt.

Only one cross-vein between these veins. ..... 5

3. Five posterior cells, both branches of the fourth vein furcate.

Rhaphidolabis Osten Sacken.
Four posterior cells, the posterior branch furcate.

Plectromyia Osten Sacken.

4. Four posterior cells; wings pubescent. . . . Ula Haliday.
Five posterior cells ; wings bare. . . . . . . . 5

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

the wing. ...... Amalopis Haliday.

Anterior cross- vein at a very oblique angle with the longitudinal axis of
the wing and parallel with the posterior cross-vein.

Pedicia Latreille.

CYLINDROTOMINI.

1. Five posterior cells; colors yellow and Jalack.

Cylindrotoma Macquart.
Four posterior cells. 2

2. Antennal joints subcylindrical, elongated 3

Antennal joints subglobular ; head and thorax conspicuously punctulate.

Triogma Schiner.

3. Colors yellow and black Liogma Osten Sacken.

Colors brownish and grayish. . . . Phalacrocera Schiner.

PTYCHOPTERIN^.
1. First submarginal cell much shorter than the second.

Idioplasta Osten Sacken.
First submarginal cell much longer than the second. ... 2



36 NORTH AMERICAN DIPTERA.

2. Three posterior cells Bittacomorpha Westwood,

Four posterior cells Ptychoptera Meigen.

TTPULIN^.

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 unusually slender, anterior branch of second vein present and
oblique. . - . . . • • • . . • 5

2. Antennge thirteen-jointed; male forceps complex.

DoLicHOPEZA Curtis.
Antennae with less than thirteen joints ; male forceps small, simple. 3

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

MEGiSTOCEPtA Wedemann.
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 Osten Sacken.
Head more closely applied to the thorax ; seventh vein terminates in the
margin at some distance from the anal angle.

Tanypremna Osten Sacken,

5. Antennae of $ pectinate or sub-pectinate 6

Antennae not pectinate. ........ 7

6. Ovipositor of 9 long, sword-like. . . . Xiphura BruUe.
Ovipositor of 9 lo"g but not sword-like. . Ctenopiiora Meigen.

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

sometimes arising together but the petiole always short,

Pachyrrhina Macquart.

Two posterior veins arise from the discal cell the anterior one furcate,

petiole always of considerable length. ..... 8

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

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

minute bristles. Holorusia Loew.

Two marginal cells. 10

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

LoNGURiA Loew.
Abdomen less elongate; antennae with thirteen joints. Tipula Linne.



BIBIONID^. 37

10. BIBIOXID^.

Moderately slender flies, of from three to ten millimeters in
length. Head usually somewhat flattened; front in the male
very narrow, or the eyes contiguous ; face short ; eyes round
or reniform, often densely hairy in the male ; ocelli large,
distinct. Antennae with from nine to twelve joints, cylindri-
cal, not longer than the head and thorax together, the joints
closely united. Proboscis not long, with thickened, hairy
labella ; palpi variable, sometimes long, with four or five dis-
tinct joints, at other times short. Thorax without suture ;
scutellum half round. Abdomen composed of seven or eight
segments, not short. Legs moderately long and strong, the
hind pair more or less elongated, the front femora thickened ;
front tibiae usually with a stout hook or coronet of spines at
the tip ; pulvilli and empodium distinct, the latter often pul-
villiform. Wings large, the anterior veins stouter than the
posterior ones; costa not extending on the posterior margin ;
second longitudinal vein wanting, the third arising from the
first ; third vein sometimes furcate ; fourth usually furcate ;
first basal and sometimes the second basal cell present ; no
discal cell.

This family comprises about three hundred described species
and is of wide distribution. The larvse are cylindrical, foot-
less, with transverse rows of bristles, usually with eyes ; they
feed on excremental or vegetable substances, especially on the
roots of grass. The pupse are inactive, mostly free, living
in excavated, smooth, oval cavities near the surface of the
ground, which the larvse have prepared before undergoing
their metamorphosis, and where the pupse remain before
emerging in the perfect form. In some species the males
differ very markedly in coloration from the females, so much
so that they are commonly mistaken for different species ;
they are easily distinguished for their very large eyes which
comprise nearly the whole head and are covered with hairs.
One of the most common species is Bihio albijjennis which



38 NORTH AMERICAN DIPTERA.

occurs early in the spring, in great numbers, especially about
willows, and i-ii gardens. It is conspicuous for its white wings
and black color, and like most other members of the family is
slow in its movements, flying heavily. B. femorata, a com-
mon species, is of a deep red color with black wings. B. tristis
has been observed in large numbers in many Kansas wheat-
lields, during the last week of April, apparently without
causing damage.

1. Second basal cell present 2

Second basal cell wanting 5

2. Third longitudinal vein furcate 3

Third vein not furcate. ......... 4

3. Palpi four-jointed ; first antennal joint elongate. Hesperinus Walker.
Palpi five-jointed. . . . . . . Plecia Wiedemann.

4. Front tibias with a stout, spine-like process at the tip. Bibio Geoffrey.
Front tibiae with a terminal coronet of spines. Dilophus Meigen.

5. Front tibiae ending in a spine-like process. . . Aspistes Meigen.
Front tibiae of the usual structure; third vein not furcate; hind meta-
tarsi shorter tlian the remaining joints together. Scatopse Geoffrey.



11. SIMULTIDiE.

Small flies, from three to six mm. in length, with thick,
compressed, short legs. Head hemispherical ; face short ;
eyes round or reniform, holoptic in the male ; no ocelli.
Antennas scarcely longer than the head, cylindrical, ten-
jointed; the two basal joints differentiated, the others closely
united. Proboscis not elongated, with small, horny labella;
palpi incur vate, four-jointed; the first joint short and the two
following of equal length ; the last one longer and more slen-
der than the preceding. Thorax ovate, without suture ; the
scutellum small. Abdomen cylindrical, composed of seven or
eight segments; genitalia concealed; legs strong and not elon-
gated ; femora broad and flat ; tibiae without terminal spurs ;
first joint of the tarsi longer than the following and usually



BIBIONID^.. 39

dilated in the male; the last joint very small. Wings large
and broad, with distinct alulae, anterior veins thickened, the
others slender ; auxiliary vein terminating in the costa about
the middle of the wing ; humeral cross-vein present ; second
longitudinal vein wanting, the first and third lying close by
each other; the third arising from the first rectangularly be-
fore the end of the auxiliary vein ; anterior cross-vein very
short ; fourth vein curved, forked nearly opposite the anterior
cross-vein ; the forks terminating near the tip of the wing.

The family Simuliidse, comprising about seventy -five known
species, is one of the best known popularly among diptera, on
account of the troublesome character of the flies, which are
scarcely less annoying than the true mosquito; they rarely
exceed five or six mm. in length, usually not more than three
or four, and will be immediately distinguished from the mos-
quito by their thick-set appearance, their shorter legs, their
shorter proboscis, and less slender antennae. In the southern
States they are known as "buffalo gnats" and '-turkey gnats",
and sometimes occur in almost incredible numbers ; cattle
when attacked by large numbers are driven almost frantic,
and will seek to evade them by rolling in the dust, rushing
about, or going into the water. When the flies are numerous
they will almost literally cover the cattle, especially seeking
the openings of the body, entering the nostrils and the ears,
the margins of the eyes, where they will actually lie piled
upon each other. When very numerous they will produce an
inflammatory fever, frequently terminating in death. The
well known European species is S. cohimbaczense, which during
some seasons in the regions of the Danube costs the death of
many cattle.

The larvae are very interesting creatures ; they are aquatic,
living most frequently in mountain streams, on stems of
plants, or stones, where they form for themselves elongated
cocoons, opened above. In the open end of these cocoons the
pupae ensconce themselves with the anterior part of the body



40 NORTH AMERICAN DIPTERA.

naked and free, from which extend eight or sixteen very long,
slender, threadlike breathing tubes. The perfect insect es-
capes under water and comes to the surface. The larvae are
soft-skinned, thickened at the extremities, with a cylindrical
head, two pairs of eyespots; on the first thoracic segment
there is a foot protuberance with bristly booklets; and the
end of the abdomen has several appendages for attachment.
But one genus is known in the family, Simulium, which
will be recognized from the characters already given.



12. RHYPHIDiE.

. Head nearly hemispherical ; eyes rounded, holoptic, or
nearly so in the male ; broadly separated by the front in the
female ; ocelli present. Antennae about as long as the thorax,
composed of sixteen joints, cylindrical, the two basal joints
distinctly differentiated; those of the flagellum closely united,
short-haired, gradually decreasing in size toward the end.
Proboscis moderately prominent, with small labella ; palpi
very long, four-jointed; the second joint longer and broader
than the others. Thorax convex, without transverse suture ;
scutellum semicircular, short and broad; metanotum strongly
developed. Abdomen cylindrical, composed of seven seg-
ments ; genitalia concealed or nearly so. Legs slender, with-
out spines ;• the coxse, especially the front pair, more or less
elongated ; metatarsi elongated ; tibiae without spurs or the
hind pair with minute ones ; empodia pad-like, the pulvilli
absent. Wings large, in rest lying flat upon the abdomen ;
auxiliary vein present; the costal vein reaching to the tip
of the third vein. Discal cell present, from which three
veins originate, and a fourth arises from the posterior basal
cell ; five posterior cells and two elongated basal cells present ;
a distinct stigma.

But very few species of this family are known, belonging
to but two or three genera. The typical genus Ehj/phvs con-



LEPTID^. 41

tains a number of species of wide distribution, specimens of
which are frequently found about the windows of dwelling
houses. The genus Olhiogaster has recently been described
from Mexico, " It differs from Ehyxjhus in the structure of the
head (eyes separated by a broad front in both sexes, and
occiput but very little developed), of the antennae (scapus
short, fiagellum of male filiform, etc.), of the thorax and abdo-
men, as also i^ the venation." (Osten Sacken.)

The larvae of Rhyphiis are worm-like, legless, naked, more
or less transparent, with snake-like movements ; there are two
short fleshy points at the posterior end. The pupae are free,
inactive, with two projections anteriorly ; they live in water,
brooks, pools, or puddles, or in rotting wood, hollow trees, or
manure.



13. LEPTID^.

Species of moderate or large size, more or less elongated,
usually thinly pilose or nearly bare, without distinct bristles.
Males holoptic or dichoptic. Empodia developed pulvilliform,
the pulvilli present. Tegulse small or rudimentary. Third
joint of the antennae complex or simple, with or without a
terminal or dorsal arista or terminal style. Veins of the wings
distinct, not crowded anteriorily ; third longitudinal vein fur-
cate ; basal cells large ; five posterior cells usually present.

As defined above, this family includes the Xylophagidae,
Leptidse and Coenomyidae of authors. It may be a question
whether this union is justifiable, but, on the whole, it seems
that the sole character which can be used to distinguish the
families — the structure of the third antennal joint — divides
the group unnaturally, throwing with the Xylophagidae forms
whose affinities are greatest with the Leptidae, notwithstand-
ing the antennal character.

The Xylophaginae include less than one hundred known
forms, and many of them are remarkable for their general



42 NORTH AMEKICAN DIPTERA.

resemblance to certain hymenopterous insects. Species of
Rhachicerus form a connecting link with the Nematocera, and
are apt to be confounded with the Rhyphidse, but the presence
of the pulvilli will distinguish them. The larvae are found
in decaying wood or under the bark of trees and are carnivor-
ous and predaceous, feeding upon the larvae of beetles and
other wood insects. The skin is parchment-like, the body
cylindrical. The mouth-parts and antennae are very small,
the maxillae short and hook-like. The first or the first three
segments back of the head are chitinized above ; the last seg-
ment above with a chitinized plate terminating posteriorly in
two hooks. The fourth to the ninth segments have bristly
pseudopods below. The pupae are free.

The Leptinae comprise something over two hundred known
species. They are usually of moderate size and not very active
in their habits. The larger species are commonly found in
meadows and woodlands, resting upon stems or trunks of trees
with their head downward. They are sometimes predaceous
upon other insects and the species of Symphoromyia have a
habit of sucking blood as do the horseflies. The larvae are
predaceous, living in the earth, in decaying wood or in pas-
sages made by woodboring beetles. Others live in moss, in
sand or in water. The eggs of Atherix are deposited in dense
masses attached to dry branches overhanging water. Not only
do numerous females contribute to the formation of these
masses, but they remain there themselves and die. The larvae
hatching, escape into the water. The flies of species of Ver-
mileo deposit their eggs in sand, and the larvae form conical
pitfalls in which to ensnare small insects. The tenth seg-
ment of these larvae bears above at its tip a transverse row of
long booklets directed backward, but with the hooks bent
forward ; the eleventh segment has a similar row directed
forward, the hooks of which are turned backward. On the
fifth segment below there is a simple unpaired grasping foot
which is capable of being protruded forward and downward ;



LEPTIDJ^.. 43

at its tip there are two triangular, sharp, flat, chitinous hooks,
and below them some stiff bristles. The booklets serve as
aids in boring in the sand and to fix themselves ; the organ on
the fifth segment enables the larva to seize and hold its prey,
and also in constructing the pitfalls. The larvae of the Lep-
tinse in general are cylindrical, with or without fleshy abdom-
inal legs. The last segment has a transverse cleft, the portion
above which is provided with two, often backward-bent points
or processes ; the under part is obtuse, with the two stigmata
between them.

TABLE OF GENERA.

1. Third joint of the antennge complex, the antennse more or less elongated ;

five posterior cells present. ....... 2

Antennae short or but little elongated, the third joint simple, with a ter-
minal or dorsal arista or a terminal style; face small, excavated;
proboscis short; some or all of the tibiae spurred. . Leptin^.

2. All the tibiae with spurs. Xylophagin^.

Front tibiae without spurs. . . . . . Arthroceratin^.

XYLOPHAGIN^.

1. All four posterior veins (i. e. the veins separating the posterior cells)

arise from the discal cell ; head small ; scutellum with spines.

CoENOMYiA Latreille.
The last posterior vein arises from the second basal cell, the fifth pos-
terior cell hence not contiguous at its base with the discal cell ;
scutellum without spines. ,. . . . . . . . 2

2. Third joint of the antennae acute at tip, . . Arthropeas Loew.
Third joint of antenna not acute at tip. ...... 3

3. Fourth posterior cell closed ; the third joint of the antennae much elon-

gate, composed of numerous, distinct divisions, often pectinate ; eyes

emarginate near the antennae. . . . Rhachicerus Haliday

Fourth posterior cell open ; third joint of antennae composed of eight

annuli, indistinctly separated. . . . Xylophagus Meigen.

ARTHROCERATTNiE.

1. Foiu'th posterior cell open. . . . . . . . . 2

Fourth posterior cell closed. {Subula preoc.) Subula Omyia nom. nov.



44 NORTH AMERICAN DIPTERA.

2. Face projecting on each side in a rounded, conical protuberance, thickly

covered with hair Glutops Burgess.

Face with two deep diverging furrows, running from the base of the
antennas to the oral margin. . . . Akthrockras Williston.

LEPTIN^.

1. Front tibiae with terminal spurs 2

Front tibige without terminal spurs 3

2. Front tibiae with a single spur; sometimes only four posterior cells pres-

ent in the wing Dialysis Walker.

Front tibiae with two spurs ; five posterior cells as usual.

Triptotrioha Loew.

3. Third joint of the antennse round, oval or pear-shaped, its bristle dis-

tinctly terminal. 4

Third joint of the antennae kidney-shaped, the arista more dorsal. 6

4. Anal cell open ; hind tibiae with two spurs. . Leptis Fabricius.
Anal cell closed 5

5. Third joint of the antennas with a slender arcuate bristle; hind tibiae

with one spur. . . . , . Chrtsopila Macquart.

Third antennal joint with a shorter, slender style.

( Spanta Meigen.

( Ptiolina Zetterstedt.

6. Hind tibiae with two spurs ; anal cell closed. . Atherix Meigen.
Hind tibias with a single spur; anal cell open.

Symphoromyia Frauenfeld.



14. STRATIOMYID^.

Small to moderately large, nearly bare or thinly pilose, bris-
tleless species. Head short, hemispherical or flattened, as
broad as the thorax. Ocelli present. Eyes contiguous or
separated by the front in the male. Antennae porrect, approx-
imated at the base, three-jointed, the third joint always com-
plex, usually with a terminal style or an arista. Proboscis
never elongated; palpi two or three-jointed, sometimes rudi-
mentary. Thorax never strongly convex ; scutellum often
with tubercles, spines or projection on its margin. Abdomen
composed of from five to seven segments, usually flattened,



STRATIOMYID^. 45

often elongated. Legs never thickly pilose ; without bristles,
the tibiae without spurs (except in some Beridinse); pul villi and
empodia pad-like. The costal vein of the wings does not
reach to the tip of the wing ; veins often crowded anteriorly,
and those posteriorly weak ; discal cell present ; four or five
posterior cells, and one or two submarginal cells present, the
anterior branch of the third vein short and often indistinct.

The family Stratiomyidse is one of considerable size, in-
cluding nearly one thousand known species. The flies are
invariably flower insects, seldom with any marked powers of
flight and never having the habit of hovering in the air. Not
a few species are caught in beating nets or on the windows of
dwelling houses. Many of the species have in life bright yel-
low or green markings. Their eggs are laid on the ground, on
plants about water, or perhaps on the surface of the water
itself. The larvae are carnivorous, or feed upon decaying veg-
etable material. The larvae of Chrysomyia have been found
in cow-dung, and under stones ; those of Sargus in the flowing
sap of elm trees ; those of Herm.etia in privies ; those of Pachy-
gaster in decaying wood ; those of Beris in moss ; those of
Stratioinyia, Odontomyia, Nemotelus, etc., in water. The lar-
vae of Stratiomyia have been found in salt and alkaline water.
The body is smooth and flattened, the last segment often pro-
longed into an elongated breathing tube and with a terminal
transverse cleft. The pupae are inactive, remaining within
the larval skin, the pupal skin remaining within, or partially
within, the larval skin when the fly escapes through a longi-
tudinal rent.

TABLE OF GENERA.

1. Abdomen with seven Ansible segments. .... Beridin^.
Abdomen with five or six visible segments. ..... 2

2. Three posterior veins,* all arising from the discal cell. Pachygastrin^.
Four posterior veins, the anterior ones sometimes rudimentary. . 3

* By posterior veins is meant those separating the posterior cells.



46 NORTH AMERICAN DIPTERA.

3. All the posterior veins arise from the discal cell, the fifth posterior cell

hence contiguous with the discal cell 4

The last posterior vein arises from the second basal cell. . , 5

4. Third joint of the antennae with a long, delicately fringed, lamelliform

style ; usually large, more or less elongated species ; males dichoptic

(Hermetiinse) Hermetia Latreille.

Third antennal joint not with such a style ; abdomen short.

Clitellarin^.

5. Antennae with a slender dorsal or terminal, bare or pubescent arista.

Sargin^.
Antennge never with a slender or long arista. . . Stratiomyin^.

BERIDIN^.

1. Three posterior veins, all arising from the discal cell.* . . 2
Four posterior veins, all arising from the discal cell; scutellum with

spines. ........... 6

2. Scutellum without spines. . 3

Scutellum with spines 4

3. Short, small species Allognosta Osten Sacken.

Elongate, larger species; head sometimes small. (Central and South

America) Chiromyza Weidemann.

4. Scutellum with ten spines (Central and South America).

Hetekacantha Schiner.
Scutellum with not more than six spines 5

5. Head hemispherical Beris Latreille.

Head not hemispherical, the front much flattened and elongate (Central

America). Berismyia Giglio-Tos.

0. Occiput flattened ; hind femora simple ; the last two abdominal seg-

ments small Scoliopelta Williston.

Occiput excavated ; hind femora thickened at the extremity.

Neoexaireta Osten Sacken.

SARGIN^.

1. Antennae elongate, with a terminal, pubescent style (Central and South


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Online LibrarySamuel Wendell WillistonManual of the families and genera of North American Diptera → online text (page 8 of 18)