Samuel Wendell Williston.

Manual of North American Diptera online

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more than once, arbitrarily and without giving reasons,
rejected the earlier names of genera and species for ones
of his own creation, and the present seems to be one of
the most flagrant examples. The description and figure


of Payitophthahnus tabaninus Thunberg leiave no doubt
of the form to which they apply, and the description was
published two years earlier than that of Acanthomera, and
was quoted by Wiedemann. Possibly Wiedemann thought
the name inappropriate, but, to say the least, it is no
more inappropriate than his Acanthomera, in which the
'spiny femora' may be only an individual character, cer-
tainly not generic.

The relationships of the family are very close indeed
to the Stratiomyidae, and the families might, very prop-
erl}^ be united.



Fig. 63. Taba7ius lineola\ enlarged. After Lugger.

Head large, the occiput flattened or concave. Antennae
porrect, the third joint composed of from four to eight
segments or annuli. Byes large, pubescent or bare, con-
tiguous above in the male, and often with some of the
facets much larger than the others; in the living insect
of either sex usually with green or purple bands or spots.
Ocelli present or absent. Proboscis projecting, some-
times as long as or longer than the body ; palpi two-joint-
ed, that is with one movably articulated joint, which is
variable in length and thickness in different genera.
Thorax and abdomen clothed with fine hairs, never with
bristles. Abdomen broad, never constricted at the base,
composed of seven visible segments ; genitalia never
prominent. Legs moderately stout, the tibiae sometimes
much dilated; middle tibiae always with two spurs at
tip; empodium developed pulvilliform, the pulvilli al-
ways present. Wings but little variable; two submar-




ginal and five posterior cells always present ; basal cells
large, anal cell usually closed, but never far before the
border of the wing; the marginal vein encompasses the
entire wing. Squamae of considerable size. Flies of mod-
erate or large size, never slender; rarely with brilliant

Fig. 64. Pangonia guttata; enlarged.

This family includes the insects commonly called horse-
flies, green-headed flies, etc., and has a wide distribution
over the world. About eighteen hundred species have
received names, of which not less than two hundred and
seventy-five are from North America. None of the spe-
cies are active on dark, cloudy days, though some are
partial to shady woods, and are very annoying to stock
in such places. On clear, warm days, horseflies begin
flying as soon as the sun has warmed the air, and are


usually most active toward the latter part of the fore-
noon, although they are plentiful about cattle and horses
during most of the time while the sun is shining. The
females only are bloodsucking in habit; the males feed
upon the juices of plants, the honey-dew secreted by
plant-lice and scale insects, and similar substances.
The females also will feed as the males do, when nothing
more to their liking is procurable. Their bites are pain-
ful, but are not usually attended with that inflammation
or swelling characteristic of the mosquitoes andpunkies.

Most species of Tabanidse may be collected in various
situations. Sweeping the grasses and weeds of marshy
places, collecting from fences and trunks of trees in the
early morning, or from plants much infested by plant-
lice or certain scale insects throughout the day, netting
specimens that fly about stock or the collector's own
head, or that may be found upon various flowers, or cap-
turing such as may enter the doors and alight upon the
windows, all are productive of results. Collections made
in these ways are pretty sure to represent well the tabanid
fauna of any locality.

The eggs of the Tabanidse are deposited in large masses
on the stems and leaves of plants or in similar places
over water or in marshy land. They are spindle-shaped,
brown or black in color, and, in ordinary summer temp-
erature, hatch in from seven to nine days The larvae
feed upon various small creatures, and in such cases as
have been observed reach maturity and change to pupae
the following spring. The pupal stage is completed in
three or four weeks, the whole cycle from the deposition
of the eggs to imaginal maturity thus requiring about
eleven months for its completion. The larvae may be
sought for in rotting logs and stumps, in the soil in the
vicinity of ponds, under stones about ditches, or swim-



ming free in the water; indeed one may occasionally find
them in the most unexpected places. The pupae are
difficult to find in nature, though they usually rest near
the surface of the ground wherever the larvae come to
maturity. I^arvae taken in the spring are easily reared
in jars of moist earth on a diet of angle worms; but only
a single specimen can be reared in each jar, for they are
cannibalistic in nature. The body of the larvae is eleven-
segmented, each segment usually encircled by a row of
fleshy protuberances, which are most pronounced on the

Fig. 65. Tabanidse. i, Tabanus, wing; 2, 3, Tabanus, antennae,
4, Dichelacera, antenna; 5, Snowielliis, head, side; 6, H csniatopota
head, in front; 7, Diachlorus, head, front; 9, Lepidoselaga, front leg;
\o,StibasO}na,\&%\ 11, Chrysops, head; 12, Chrysops, leg; 13, Goniops,
head, front; 14, Silvius, antenna; 15, Apatolestes, head, front; 16, Pity-
ocera, antenna (CTi<<lio-Tos) . FignresbyJ. S. Hine.


ventral side, where they serve as prolegs. The head is
small, but distinct, and the mouth-parts are peculiar;
the mandibles are two strongly chitinized pieces which
work antero-posteriorly ; when they are retracted the an-
terior ends point directly forward, but when protruded,
they point downward and backward, thus forming a pair
of hooks by which the prey is held.


1 . Hind tibiae with spurs at tip , . . . 2

Hind tibiae without spurs at tip. ...... 8

2. First six segments of the third joint of antennae each produced

into a pair of long processes (16). . . . Pityocera.
None of the segments of third joint of antennae produced into lat-
eral processes. ......... 3

3. Third joint of antennae composed of five segments, the first of

which is much longer than the following ones; ocelli present. 4

Third joint of antennae composed of eight segments, the first of

which is only slightly longer than the following ones. . 5

4. Second joint of antennae only half as long as the first (14) .


Second joint of antennae distinctly more than half as long as the

first (11, 12) Ohrysops.

5. Fourth posterior cell of wing closed {Dielisa). . . Scione.
Fourth posterior cell open. ....... 6

6. Eyes of female acutely angulated above; wings in both sexes dark

on anterior part, hyaline behind (13) . . . Goniops.

Eyes of female not acutely angulated above; wings nearly uniform

in color or hyaline. ........ 7

7. Front of female wide; much wider below than above; proboscis

only a little longer than the palpi (15) . . Apatolestes.

Front of female of normal width or narrow; its sides usually par-
allel; ocelli present or absent; proboscis often long or very long.


8. Third joint of antennae composed of four segments; front of female

very wide (6) Hamatopota.

Third joint of antennae composed of five rings or segments; front
of female not unusually wide. ...... 9


9. Third joint of antennae with a distinct basal angle or process
above. .......... 11

Third joint of antennae not with a process or distinct angle

above. .......... 10


10. Front of female narrow; front tibiae rather broad (7) .


Front of female of normal width; front and middle tibiae greatly
dilated (9). Lepidoselaga.

11. Hind tibiae ciliate with long hairs. ..... 12

Hind tibiae not ciliated. ....... 13

12. Third antennal joint with a very long basal process, the annulate

portion short; front tibiae dilated (10). . . Stibasoma.

Third antennal joint with a basal prominence; antennae situated

on a projecting prominence (5). . . . Snowlellus.

13. Basal process of third antennal joint unusually long, at least reach-

ing the third ring of the joint; body long (4) Dichelacera.

Basal process of third joint often short or obsolete, at most not

reaching the end of the first segment (2, 3). . Tabanus.

A. Kyes pubescent; an ocelligerous tubercle present in the male.

Therioplectes .

B. Eyes bare; no ocelligerous tubercle. . . Tabanus.

C. Kyes pubescent; no ocelligerous tubercle. . Atylotus.


Fig. 66. Opsebius pterodontinus, en\a.rged.. After Lugger.

Small to large, never elongate, pilose or nearly bare
flies. Head small or very small, formed chiefly by the
large eyes, which are usually contiguous in both sexes
above or below, or above and below the antennae; three,
two or no ocelli present; antennae composed of two or
three joints, with or without a terminal arista or bristle.
Proboscis rudimentary or long, sometimes very long.
Thorax large, spherical; squamae very large and inflated;
scutellum large. Abdomen closely united to the thorax,
large and inflated. Legs rather stout; the tarsi with
three membranous pads under the claws. Venation
variable, the veins sometimes weak and indistinct; often
a supernumerary cross-vein between the third and fourth

This family, the Cyrtidae or Acroceridae, comprises a
small number of curious flies with curious habits. The}^




are easily recognizable by their small head and large, in-
flated squamae. No family characters can be drawn from
the venation, owing to the great differences often exist-

Fij<. 67. Cyrtidae. i, Acrocera, wing; 2, Acrocera, head; 3, Phi-
lopota, wing. 4, Philopota, head; 5, Oncodes, wing; 6, Oncodes, head;
7 (number removed by engraver), Pterodontia, wing; 8, Pterodontia,
head; 9, Ooicca, wing; 10, Ocncca, head; 11, Eulonchus, wing; 12,
Eulo>ichus, head; 13, Lasia, wing; 14, Lasia, head.


ing between forms otherwise related. In the few forms
in which the larvae are known they are parasitic upon
spiders or their cocoons. 'In the spring of 1887, while
hunting for spiders, I found hanging in cobwebs several
soft white maggots and pupae. The webs were generally
old and out of repair, and a closer examination showed
that no living spider was in them, but almost every one
had an empty skin of a common spider Amaurobius sylves-
tris, nearly full grown. The skin of the legs and thorax
was not clean like a moulted skin, but dirty and opaque,
as though eaten out, and the skin of the abdomen when
present was torn and shriveled. From this I concluded
that the maggots came out of the spiders, and from their
size must have nearly filled them. The maggots varied
considerably in size, the largest being a quarter of an
inch long, while others w^ere not more than half as large.
The hinder half of the body was thicker than the front
half and nearly spherical. They hung head downward,
holding to the web by their jaws and were also partly
supported by threads under and around them.' The
author of the foregoing, J. H. Emerton, reared from other
specimens of these larvae a fly belonging to the genus
Aciocera. The larvae of Astomella lindelii, according to
Brauer, are so lodged in the abdomen of the spider that
the posterior terminal stigmata are in relation with the
lung-tubes of the spider. The eggs are said to be de-
posited on dried twigs.


1. Antennae without terminal arista or style. .... 2
Antennae with a terminal arista. ...... 3

2. Antennae short, third joint rounded, with terminal bristly hairs. 3
Antennae elongate. ........ 7

3. Antennae inserted below the middle of the head in profile. . 4
Antennae inserted above the middle of the head. ... 6



4. Wings with a stout costal spur near the tip of first vein (7, 8)

Wings without such spur. ....... 5

5. Proboscis small or vestigial"^ {5,Q). . . . Oncodes.
Proboscis elongate, directed backward; prothoracic lobes broadly-
united above (3, 4) . Philopota.

6. Venation complete; eyes pilose (fig. 66) . . , Opsebius.
Venation more or less obsolete; eyes bare (1, 2). . Acrocera.

7. Proboscis very small, vestigial. ...... 8

Proboscis elongate. ......... 10

8. Kyes bare. . ^ Appeleia.

Eyes pilose or pubescent. ....... 9

9. Third joint of antennae with terminal bristly hairs. Pialeoidea.
Third antennal joint not with terminal bristly hairs (9, 10).


10. Ocelli wanting; large flies (13, 14) . .... Lasia.
Ocelli present; moderately large flies (11,12). . Eulonchus.

* Compare Nothra ainericmia Bigot. The occurrence of this genus
in North America is doubtful. If, however, Bigot correctly recognized
it, the species should be sought for under Oncodes.


Species of moderate size, not elongate, thinly or densely
pilose. Venation complicated; the fourth and fifth veins
are curved forward to terminate before the tip of the wing;
the anterior cross-vein is obsolete, that is the third and
fourth veins coalesce for a short distance; basal cells
long. Antennae small, short; third joint simple, with a
terminal, slender, jointed style. Proboscis sometimes
elongate. Ovipositor of the female elongate, often slen-
der. Tibiae without spurs; empodia developed pulvilli-
form, but, with the pulvilli often minute. (See fig. 69.)

Fig. 68. Wing of Rhynchocephalus volatiais.
a, third submarginal cell; b—-t\ first — fifth posterior cells.

Throughout the world about one hundred species of
this family are known, the larger part of which are from
South America and Australia. Only six species are
known from North America and two or three from all
Europe. Some of the species have the wings with nu-
merous cross-veins, almost recticulate in appearance.
Megistorhynchus longirostris from Africa, though only
about two-thirds of an inch in length, has a proboscis
nearly three inches long. The adults are flower flies,
resembling in their habits the Bombyliidse.

But little is known of the larvae. The females of Hii^-
Tnoneura obscura have been observed laying their eggs
deeply within the burrows of Afithaxia, a wood-boring



insect, in the pine rails of fences. The eggs were found
in clusters and the young larvae hatched from them differ-
ed very singularly from those of a more mature growth.
They were more slender, but differed chiefly in having each
of the abdominal segments from the sixth to the twelfth
provided with a pair of false legs bearing a single elon-
gate seta at the tip, the hooks pointing backward; on the
thirteenth segment there were two pairs of similar setae,
the hooks of which, however, pointed forwards, thus en-
abling the larva to attach itself firmly and raise itself
erect. These young larvae issued in great numbers from
the burrows in which they were hatched and, placing
themselves erect, were blown away by the wind. Here
for a time they have not been followed, but it is probable
that they attach themselves by the aid of the ventral
hooks to the bodies of large-sized beetles, by which they
are carried into the ground when the females enter to de-
posit their eggs. This is probable from the fact that
hundreds of pupae and pupa skins were observed near
the fence. On. searching below these the larval skins
were found at a depth of about two inches, and still deeper
were found the remains of the beetles, Rhizotrogus solsti-
tialis, in some instances with the larvae yet within them.
Females of Rhynchocephalus sackeni have been observed
by Bruner apparently depositing eggs in the stems of
Eriogonum alatuTn.

I. Proboscis short, protruding but little from the oral opening; eyes
bare or pilose; two or three submarginal cells. Hirmoneura.

Proboscis long; antennae broadly separated; eyes bare; ovipositor
composed of two slender lameilse; three submarginal cells
present (fig. 68). .... Rhynchocephalus.


Rather large, elongate, chsetophorous, thinly pilose
flies. Antennae three-jointed, with or without a small,
short style. Front not excavated, broader in the female.
Ocelli present. F'ace short. Proboscis not adapted for
piercing, the labella not horny. Third longitudinal vein
of wings usually furcate; basal cells large; five posterior
cells present. Bmpodia wanting. Male forceps enlarged.

Fig; 71. Apioceridae. Apiocera hartispe.v, head; 2, Apiocera har-
uspex, wing; 3, Apiocera, sp. (Australia! wing; 4, Apiocera (gen. nov.
Australia) wing ; 5, Rhaphioniidas acton, head ; 6, Rhaphioniidas
acton, wing.

Less than a score of species of this family are known
throughout the world, seven of which have been de-
scribed from North America. The genera have been
variously placed among the Mydaidse, Asilidse and


Fig. 69. Trichophthalma, species (Nemestrinidae); enlarged.

Fig. 70. Apiocera, species; enlarged. (Australia.)


Therevidae, but seem best isolated into a distinct group,
though the relationships of Rhaphiomidas with the My-
daidse are evident; perhaps as close as with Apiocera.
The members of the genus Apiocej'a have much the ap-
pearance of large Therevidse or of Asilidse, from which
they will be at once distinguished by the anterior curva-
ture of the third and fourth veins of the wings. The
larvae are unknown. See fig. 70.

I. Palpi two-jointed, large; the second vein from the discal cell ter-
minates beyond the tip of the wing (1, 2) . . Apiocera.
Palpi one-jointed, small; the second vein from the discal cell ter-
minates before the tip of the wing; proboscis elongate {Aponii-
das) {5,Q) Rhaphiomidas.


XX. Family MYDAID^.

Rather large to very large (see fig. i, page i6), thinly
clothed or bare, elongated flies. Venation complicated,
the basal cells long, the fourth vein always terminating
at or before the tip of the wing; posterior branch of
fourth sometimes present and terminating also before the
tip of the wing, as in Rhaphiomidas (Apioceridae), but
not present in American species. Antennae composed of
-four joints, the fourth always, the third usually elongate.
Front excavated betv\^een the eyes; both sexes dichoptic;
ocelli wanting. Proboscis with fleshy labella, and with-
out palpi (in our species). Kmpodia very little devel-
oped, not pulvilliform.

Fig. 72. Mydaidse. i, Dolichogaster, wing; 2, Dolichogasier,
antenna; 3, Mydas, antenna.

The family Mydaidae comprises only about a hundred
known species, more abundantly represented in Austra-
lia, Africa, South and Central America. The family


MYDAID^. igj

comprises the largest of known diptera. The relation-
ships of the family are very close with Rhaphiomidas of
the Apioceridse, through the Tricloninae.

The larvae of species of Mydas live in decaying wood,
and it is probable that other members of the family have
similar habits. They are known to be predaceous in
some cases upon the larvae of beetles. The larvae of M.
fulvipes are nearly two inches in length, with swellings
below the abdominal segments for locomotion; the body
is depressed and somewhat widened, with the posterior
extremity broader and somewhat obtuse. The pupa of
M. clavatus has at its anterior end two strong, sharp, out-
wardly curved hooks ; the first abdominal segment has
at its anterior border above, a row of very long, erect
spines, curved backward at the tip. Another series of
spines is situated on the anterior border of the last seg-
ment; and, on the same segment there is a pair of hooks
at the tip curved downward.


1. Terminal segment of the female abdomen with a circlet of spines. 3
Terminal segment of female abdomen without circlet of spines. 2

2. Antennae but little longer than the head, the third short and the

fourth expanded ; cross-vein between the second and fourth
posterior cells present or not (1, 2). . Dolichogaster.

Antennae much longer than the head, the third and fourth joints
elongated; the latter moderately or but slightly expanded [Vhy-
loniidas)^. (Fig. i, and 3.) . . . , . Mydas.

3. Hind tibiae of female with spur; a short vein ends in hind margin

of the wing between the second and fourth posterior cells.


Hind tibiae of female without terminal spur; no such cross- vein;

proboscis elongate. Leptomydas.

* I have examined specimens of Phylomidas phylocerus, the type
species of the genus, from Norton County, Kansas, in the University
of Kansas Museum. The genus is not valid, differing from Mydas
only in the more expanded fourth antennal joint.

XXI. Family ASILID^.

Fig. 75. Promachiis vertebratus, nsiiuraX s\7.&. After Washburn.

Species cf moderate to large size, rarely small ; usu-
ally more or less elongate in form, sometimes thickly
hairy; always bristly, the bristles sometimes conspicu-
ously strong; highly predaceous in habit. Head flatten-
ed, broad and short, separated from the thorax by a
freely movable neck. Front excavated between the eyes,
dichoptic in both sexes, the front of the male not narrow-
ed. Ocelli present, usually situated upon a rounded
tubercle; front with bristles. Antennae porrect, simple,
usually composed of three simple joints, the third more
or less elongate, and wnth or without a terminal style or
arista, the bristle exceptionally pectinate; sometimes
the so-called style is thickened, forming one or two an-
tennal joints. Proboscis never markedly elongate; firm
and horny, adapted for piercing, directed downward, or
downward and forward; labella never fleshy; palpi com-
posed of one or two joints. Abdomen composed of eight


Fig. 73. Craspedia coriaria Life size.

Fig. 74. Erax qtiadrimaculatus . Three times natural size.



segments, tlie hypopygium and ovipositor usually promi-
nent, lyegs strong, bristly, of moderate length, rarely
elongate and slender; tarsi strong; empodium bristle-
like (31) or wanting, the pulvilli rarely vestigial. Squa-
mae small. Wings when at rest lying parallel over the
abdomen; basal cells long; two or three submarginal
andfive posterior (four in Townseiidia and Leptopfero?nyia,
35) cells present; first and fourth posterior and the anal
cells closed or open. (Figs. 73 and 74.)

The family Asilidae, or Robber-flies is one of the larg-
est and best known among diptera, including about three
thousand species, distributed in more than one hundred
and fifty genera. Many of the species are conspicuous
for their large size, the largest measuring nearly two
inches in length, while the smallest known species is
over four millimeters. They are, perhaps, the most pre-
daceous of all flies in their habits. The greater part of
them rest upon the ground in wait for their prey, arising
with a quick buzzing sound when disturbed, to alight a

short distance beyond. Some of
the lyaphrinae have a striking
resemblance to humble bees, and
are usually observed resting up-
on foliage about the borders of
forests. All their food, which
consists wholly of other insects,
is caught upon the wing; their

luckless victims when once seiz-
Fig. 76. DasyUis, species; j 1 ^1. • . z .

natural size. After Kellogg, ^d by their strong feet are pow-
erless to escape. Their prey is
usually other flies and h3anenoptera, but flying beetles,
especially the Cicindelae, are often caught, and they are
known to capture and destroy large dragonflies. In one
instance that the writer observed, a female seized a pair
of her own species, and thrusting her proboscis into the






Fig. 76. Asilidse. i, Leptogaster, wing; 2, Leptogaster, antenna; 3,
Leptogaster, end of tarsus (claw mostly cut away); 4, Datnalis occi-
dejilalis, antenna.; 5, Dicraniis jaliscoerisis, claw; 6, Stenopogon {Scle-
ropogon) truquii, antenna; 7, Microstyluni galactodes, wing; Psilo-
ciirus, sp. antenna; 9, Laphystia^ species, antenna; 10, Ceraturgus
cruciatiis, head; 11, Myelaphus nielas, head; 12, Dioctria nitida., anten-
na; 13, Blepharepiumcoarctatiini, claw; 14, Der oiny ia winthefui, Yfing;
15, Deromyia, antenna; 16, Lestoniyia fraudigera, head; 17, Taracti-
cns, tibial spur; 18, Taracticus, antenna; 19. Cophura, antenna; 20,
Nicocles rufus, wing; 21, Pseudorus, tibial spur; 22, Atomosia puella,
wing; 23. Pogonosonia dorsata, wing; 24, Dasylechia {Hyperechia)

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Online LibrarySamuel Wendell WillistonManual of North American Diptera → online text (page 12 of 25)