Samuel Wendell Williston.

Manual of North American Diptera online

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do not believe that the reverse is probable — the Acalypterse
have not descended from the Calypterse, for instance, and these
latter are, in this respect at least, as in others, the more highly
specialized insects, just as Bibio is more highly specialized than

7. L,oss of ocelli; diminution and loss of the compound eyes, espe-

cially characteristic of ectoparasites.

8. Diminution in number of abdominal segments; the closer fusion of

the thoracic segments.

9. IvOss of tarsal joints; loss of empodium.

These of course are not all the lines of evolution in
diptera, but I believe that they are all irreversible, that
evolution has never recovered anything once function-
ally lost. Moreover all, or nearly all these lines of evo-
lution are polyphyletic, resulting in numerous cases of
parallel resemblances which must be taken into account
in any attempt at true classification. Heteropeza among


the Cecidomyidse is an excellent example of extraordina-
ry reduction of wing veins, palpal joints and tarsal joints,
though it still retains the primitive antennae and other
primitive characters which ally it with the more gener-
alized forms of diptera. In other words, the evolution of
characters in the different lines of descent does not pro-
ceed pari passu, and opinions will always differ as to the
different values to be assigned to the specialized char-
acters. Nycteribia and Melophagtis are perhaps the most
highly specialized of all insects, that is they have traveled
further from the starting point. We do not for that
reason deem them the most typical of insects, the most
highly developed — far from it.


Flies must be collected with much more care than can
be safely used with such insects as coleoptera. Moisture
of all kinds injures or ruins them, and specimens collected
in alcohol are worthless. For this reason the collecting
bottle should be lined throughout with blotting paper,
and the cyanide placed in the cork; a very little poison
suffices to kill them. Nor should they be allowed to be-
come too dry before pinning. The pin should be thrust
through the middle of the thorax, and the specimen
placed just so as to enable the head of the pin to be grasp-
ed by the thumb and finger safely. Very small speci-
mens should never be glued to card points, as is commonly
done with coleoptera; they should always be pinned.
Sometimes specimens may be collected and packed in
some very fine, light sawdust impregnated with carbolic
acid, where it is inconvenient or impossible to pin them.
Such specimens being gently separated from the sawdust
are allowed to remain for some hours, over, but not
touching, damp sand before pinning. To pin the small


specimens, use narrow strips of good card-board or blot-
ting paper, thrusting a slender pin through one end and
allowing it to protrude just a little above the edge and
clipping off the longer end with a pair of pliers. Thrust
the point of the pin as held in the card-board, into the
under-side of the insect, but not entirely through it, and
a stronger pin in the reverse direction through the other
end of the small strip. The pins are to be thrust through
the card-board from edge to edge, and in consequence a
good quality is to be selected that will not split too read-
ily. The wings should never be spread, but should be
turned aside so as not to conceal the abdomen. In the
early part of the season many interesting species will be
caught with the beating-net. The pointed end of the
beating-net may be thrust, with its contents, into a bot-
tle containing a little chloroform, or into a cyanide bot-
tle, for a short time, when the specimens may be leisurely
removed. lyater in the season, flower-flies will be col-
lected from a great variety of melliferous blossoms, and
it is better to wait for the specimens to come to such blos-
soms than to go hastily about looking for them. I have
collected from a single patch of elderberry blossoms, not
a rod in diameter, more than forty species ot Syrphidse
within ten days. Not many species are to be found in
shady woods, but those species must be sought for there.
To preserve flies in the cabinet from their insect enemies,
I use naphthaline. The head of ordinary pins, when
heated red-hot, may be thrust into the common moth-
balls sold by the druggists, which when thus mounted
serve all purposes.


1. Flies of a leathery or horny structure, living parasitically upon

warm-blooded vertebrates in the adult condition, the larvae born
when nearly ready to pupate; often wingless or with vestigial
wings. .......... 65

Flies of a softer structure, not ectoparasites upon warm-blooded
vertebrates, rarely viviparous. ...... 2

2. Anal cell rarely narrowed in the border of the wing; antennae usu-

ally composed of from eight to sixteen joints and more or
less freely articulated with each other, usually longer than the
thorax; not with a differentiated style or bristle;* palpi as a
rule with four or five joints; discal cell usually absent. . 3
Anal cell, if present, closed, or much narrowed in the border of the
wing; discal cell almost always present; palpi never with more
than two joints; antennae usually composed of three joints with
a differentiated style or bristle. ..... 14



Anal cell rarely {sofne Bibionidcs, etc.) narrowed in the margin,
if present; discal cell present only in many Tipulidcs and the Rhy-
phidce; second longitudinal vein of ten furcate , the third very rarely
if ever; palpi usually -more or less elongate, composed of from, one to
five, usually four joints, rarely absent; antennce usually elongate
and verticillate, generally filif or in, rarely pectinate, com,posedoffrom.
sisc to thirty-nine joints, usually from, eight to sixteen, the joints of
the flag ellufn homomorphic and usually freely articulated with each
other, a style or arista very rarely differentiated ."^ For the m,ost
part slender, delicate flies.

3. Mesonotum with a complete, V-shaped suture (incompletely V-

shaped and sinuous in the Ptychopterinae) . Wings many-veined,
often with a complete di.-cal cell; ocelli very rarely present;
both sexes dichoptic. For the most part large, always slender,
flies with long legs; never very small. Daddy-longlegs, craneflies.

Tipulidse, 81.

* Chionea, a wingless tipulid, has the third antennal joint ending in
a slender, three-jointed style; the flagellum of the Orphnephilidae is

(8) 65


Mesonotum never with a complete V-shaped suture, rarel)' with any
distinct suture. For the most part small or very small flies. 4

4. A complete discal cell present; antennae twelve-sixteen jointed;

empodia developed pulvilliform, the pulvilli absent.

Rhyphidse, 157.
No discal cell. . . . . . . . . • 5

5. Antennae composed apparently of two joints and a terminal arista,

formed by nine or ten closely united segments; second basal

cell present and small. Rare, small flies. OrphnephilidjB, 153.

Not such flies. ......... 6

6. Wings with only a few longitudinal veins and no apparent cross-

veins, almost always hairy; antennae slender, usually twelve
to sixteen-jointed; coxae not elongate; tibiae without terminal
spurs; legs not thickened; ocelli present or absent. Small or
minute, delicate, mostly gall producing flies.

Cecidomyidae, 117
Not such flies. 7

7. Ocelli present.* 12

No ocelli. ........... 8

8. The marginal vein is not continuous beyond the tip of the wing. 9
The marginal vein encompasses the wing; second and fourth long-
itudinal veins furcate; many veined. .... 10

9. Antennae slender; the joints more or less constricted, and often

bushy plumose in the male; legs slender, the femora sometimes
thickened; abdomen slender, wings usually narrow; no sexual
holopticism. For the most part slender, delicate gnats; some
small forms blood-sucking ('punkies',) Chironomidse, no
Antennae always shorter than the thorax, composed of ten or
eleven closely united segments, and never plumose; legs strong,
the hind pair more or less dilated; body thick -set, the abdomen
ovate; anterior veins of wings stout, the posterior ones weak
(compare certain Bibionidae when in doubt as to the ocelli) ;
males holoptic. Small or minute, blood-sucking flies; black
flies, buffalo gnats, turkey gnats. . . Simuliidse, 144

10. Wings ovate or pointed, with numerous longitudinal veins, and
without apparent cross-veins; veins very hairy; tibiae without

* The presence or absence of ocelli is not a family character; a few
forms among both the Mycetophilidae and Bibionidae appear to lack



terminal spurs. Small or minute, moth-like flies, the wings
when at rest folded roof-shaped; rarely {Phlebotomus) blood-
sucking Psychodidae, 92.

Anterior cross-vein near middle of wing, distinct; second basal
cell large and distinct; wings not folded roof-like when at
rest II

11. Wings tomentose; fringed on the hind margin; antennae of male

usually bushy plumose; the second and third veins separate at
an acute angle. For the most part blood-sucking flies; mos-
quitoes Culicidse, 96

Wings bare; the third vein arises from the second near the middle
of the wing, apparently continuous, the second vein arching
suddenly forward; never blood-sucking in habit. Dixidae, 94

12. Wings with a spider-web-like secondary venation.

Blepharoceridse, 148
Wings not with such secondary venation. .... 13

13. Coxae much elongate (moderately so in the Sciarinae) ; antennae

usually elongate, the joints usually with constrictions between
them; three or two ocelli present; in the latter case one situated
near each eye and sometimes perceptible with difficulty; rarely
the ocelli appear to be entirely absent; no sexual holopticism;
all the tibiae spurred; second basal cell never complete.

Mycetophilidae , 131
Coxae short; the thorax not strongly arched above; antennae usu-
ally shorter than the thorax and closely jointed without marked
constrictions, sometimes 14-16 jointed, longer and slender; legs
usually strong, the pulvilli usually present (Bibioninae) ; eyes
of male often large and holoptic; second basal cell often com-
plete. ... .... Bibionidse , 140


Anal cell closed bejore the border of the wing or distinctly narrowed
in the border; if absent or very short the antennce are composed of
two or three simple joints with or zvithout a style or arista. Palpi
rarely elongated, never with more than one freely articulated joint,
that IS two-jointed or one-jointed or absent. A7iten7ics: (a) elongate,
composed of distinctly separable joints, the joints of the ftagellum ho-
momorphous and sometimes as many as thirty in number; (b) com-
posed of not more than ten closely united joints without style; (c)
the so-called third joint is complex, that is, composed of from four
to eight segments or annuli, the distal one or ones usually differ-


entiaied into a style or arista; (d) composed of three simple joi?its
[sometimes apparently two), with or without a differentiated, one to
three-jointed, style or arista. Second vein of the iving 7iever furcate,
the third often; discal cell almost always present.

14. Antennae composed of two or three simple joints, the distal one

not annulated nor segmentated, usually with a one to three-
jointed terminal or dorsal arista or terminal style (d) , . 18
Antennae of the structure of (a), (b) , or (c). . . . 15

15. Kmpodia undeveloped or bristle-like; antennae elongate, the fla-

gellum composed of two or three joints, without apparent style;
front concave between the eyes in both sexes. ... 25
Kmpodia developed pulvilliform; fiagellum of antennae with nu-
merous, distinct joints, or forming the complex, so-called third
joint, with or without a differentiated style or bristle; body not
bristly. .......... 16

B. Antennce composed of more than five joints, or the third-joint
complex, four to eight segmented, inclusive of style or arista ivhe7i

16. Squamae rather large; third longitudinal vein furcate; five poste-

rior cells always present; the costal vein encompasses the wing;
fiagellum composed of from four to eight segments, never with
style or arista; males holoptic; proboscis of female adapted for
piercing. Horsefiies, gadfiies, greenheaded flies.

Tabanidae, 176

Squamae small or vestigial; for the most part flower flies; males

usually holoptic. . . . . . . . . 17

17. Tibise without spurs; wing veins not crowded anteriorly; third

antennal joint composed of seven annuli with a terminal slender
style or arista; two submarginal, five posterior cells always pres-
ent, the fourth closed. Very large, robust, southern flies.

Acanthomeridse, 173

Tibiae almost invariably without spurs; longitudinal veins of the
wings usually more or- less crowded anteriorly, the posterior
ones often weak; the costal vein does not reach beyond the tip
of the wing; scutellum often with spines; third vein almost al-
ways furcate; four or five posterior cells, the fourth rarely or
never closed; antennae long or short (b) , (c).

Stratiomyidse, 164

The middle tibiae, at least, with distinct spurs; the costal vein en-


compasses the wing; third vein always furcate; five posterior
cells present, the posterior veins not evanescent; antennae (a) ,
(b), (c) , . Leptidse, pt. 157

BB. Third joint of antenncs si^nple, not composed of annuli, with
or without a differentiated style or arista.

18. Antennae apparently two-jointed, with a three-jointed arista; wings

(rarely wanting) with several stout veins anteriorly and other,
weaker ones apparently connected with them and running ob-
liquely across the wing. Femora flattened, the hind ones elon-
gated; antennae situated low down. Small, hunchbacked, quick
running, bristly flies. . . . . . Phorid^e, 236

Not such flies, the antennae almost invariably with three easily
distinguishable joints, ....... 19

19. Bmpodia developed pulvilliform, that is three nearly equal, mem-

branous appendages on the under side of the claws. . 20

Bmpodia wanting, vestigial or linear, not developed like the pul-

villi 22

20. Squamae very large; thorax and abdomen inflated; head small,

eyes relatively large; antennae and venation variable.

Cyrtidse, 182
Squamae of moderate size, or small. . . . . . 21

21. Middle tibiee at least with spurs; no bristles on femora or tibiae;

third vein furcate; five posterior cells present (four sometimes
in Dialysis and Misgoniyia) ; anterior cross-vein always dis-
tinct; third joint of antennae with a bristle or slender style,
usually terminal. Leptidse, pt. 157

Venation intricate, the third and fourth veins often coalescent for
a short distance; tibiae without spurs; antennae with a slender,
three-jointed style; usually hairy. . Nemestrinidae, 186

22. Third longitudinal vein furcate; two or more submarginal cells

present. .......... 23

Third vein not furcate, but one submarginal cell. . . 31

23. Arista or style of antennae always terminal when present. 24
Arista dorsal Bmpididse, pt. 218

24. Front distinctly hollowed oiit between the eyes; eyes of males

never contiguous; basal cells large; mostly large flies. . 25
Front plane or convex; males often holoptic. , . . 26

25. Proboscis with fleshy labella at tip; venation complicated, the

fourth vein curves forward to terminate before the tip of the


wing; palpi small or wanting. I^arge to very large, bristleless

flies Mydaidse, 190

Proboscis without fleshy labella at tip, horny and rigid; five pos-
terior cells almost always present; palpi usually prominent.
Mostly large, bristly, predaceous flies. . Asilidse, 192

26. Five posterior cells in the wing; basal cells large. . . 27
Not more than four posterior cells.* ..... 29

27. Venation intricate; empodia and pulvilli membranous, but fre-

quently minute (see 21)..
Venation not intricate, the anterior cross-vein always apparent. 28

28. The fourth vein terminates before tip of wing; male sexual organs

prominent; males dichoptic. . . . Apioceridse , 188
The fourth vein terminates beyond the tip of the wing; male sex-
ual organs small; males often holoptic. . Therevidse, 205

29. Third antennal joint without bristle or style; three posterior cells,

the first narrowed or closed; the fourth vein terminating at or

before the tip of the wing. . . . Scenopinidae, 208

Third antennal joint usually with a terminal style; four or three

posterior cells; the fourth vein terminates beyond tip of wing. 30

30. Anal cell narrowly open or closed near border of wing (if discal

cell wanting, see Hilariniorpha p. 157, footnote) ,

Bombyliidse, 210

Anal cell closed remote from border, sometimes absent; discal cell

not rarely absent. ..... Empididse, 218

31. Wings pointed; no cross-veins, save at base; second basal cell

short; arista terminal; small flies. . Lonchopteridse, 240
Wings not lanceolate. ........ 32

32. Anal cell elongate, acute, closed toward or near the border of the

wing; second basal cell usually long. .... 36

Anal cell, if present, short, closed remote from the border of the
wing, not acutely produced (rarely produced in a narrow, lobe-
like prolongation.) ........ 33

33. Second basal cell confluent with discal cell, or the discal cell ab-

sent; auxiliary vein usually vestigial or indistinct; anal cell
often absent; usually small flies. ..... 34

Second basal cell separated by a cross-vein from a complete discal
cell; auxiliary vein and anal cell usually complete. . 40

* Five in a very few species of Bombyliidae.


34. For the most part brilliantly colored, predaceous flies; face of male

usually narrower than that of female; arista dorsal or terminal;
hypopygium often enlarged or conspicuous.

Dolichopodidse, 228
Not brilliantly colored, predaceous flies 35

35. Kyes sometimes contiguous; head small, the proboscis usually

rigid; arista usually terminal. . . Empididge, pt. 218

Kyes never contiguous; proboscis not rigid; arista almost always

dorsal. .......... 42


A frontal lumile above the base of the antenncE; third antennal joint
always simple, not annulated or complex-, with a terminal or dorsal
arista, rarely with a terminal style; third vein never furcate; never
more than three complete posterior cells present. Em,podia never pul-

36. Between the third and fourth longitudinal veins and subparallel

with them a spurious longitudinal vein; or, when rarely absent,
the first posterior cell is closed remote from the border; first
posterior cell always closed; head never with bristles, which are
rarely present elsewhere; males usually holoptic; almost always
with a dorsal arista, rarely a terminal style. Usually brightly
colored flower flies. ..... Syrphidse, 246

No spurious longitudinal vein. . . . . . . 37

37. Front broad in both sexes; antennae with a terminal style or dor-

sal arista; face usually with grooves below the antennae; probos-
cis elongate and slender, often folding; no bristles anywhere
{ConopidiE, 261.)
Not such flies; bristles almost in variably. present. . . 38

38. Hind metatarsi enlarged and ornamented, especially in the males,

males holoptic; arista terminal. . . Platypezidse, 241
Hind metatarsi not enlarged nor ornamented. ... 39

39. Head large, composed chiefly of the eyes, the front in the males

narrowed or the eyes contiguous; first posterior cell narrowed;
arista dorsal; rather small flies. . . Pipunculidae, 244
Head not large, subspherical, the front broad in both sexes, pro-
boscis short, not rigid; first posterior cell narrowed; legs elon-
gated {Micropezidce pt, 264) .
Head small, the front narrowed or eyes contiguous in male; first
posterior cell wide open {Empididcr, pt. 218).


40. Head small; proboscis more or less elongated; alula of wings usu-

ally vestigial {Empididce, pt. 218).
Head not unusually small; proboscis rarely elongated; arista al-
most invariably dorsal. ...... .41


Never more than three posterior cells present, the Jirst of which onhj maij he
closed or narrowed in the margin ; none of the longitudinal veins furcate ;
marginal and submarginal cells never closed; anal cell very rarely jjroduced
toward the margin of the wing {Micropezidce pt. Ortalididce, pt. etc.) Antenna
three- jointed, simple, with a hare, pubescent, pectinate or plumose arista, which
is almost always dorsal in position, never thickened into a terminal style. More
or less hristly flies.

41. Squamae large; front of male narrowed or eyes contiguous. 59
Squamae small; eyes of male not more approximated than those of

female, or if so the narrowing is due to the diminished width of
the median stripe, the borders remaining the same, the males
never holoptic; posterior callus of thorax almost always not dis-
tinct 42


SquamcB always small or vestigial. Auxiliary vein often indistinct or vestigial,
or closely approximated or fused with the first vein. First longitudinal vein
shortened, often very short. Basal cells small, the posterior ones often indistinct
or wanting. Males never holoptic, the front in this sex never markedly narrowed.
Thorax without complete transverse suture; po.sterior callosity usually absent.
Never large fies, usually small or very small.

42. Auxiliary vein present, separated from first longitudinal vein and

terminating distinctly in the costa; the first vein usually ends
near or beyond the middle of the wing; posterior basal cells
present. .......... 43

Auxiliary vein absent, vestigial or incomplete; the first vein usu-
ally ends in the costa before the middle of the wing. . 49

43. A distinct bristle on each side of the face near the oral margin, i.

e. oral vibrissae present. ....... 44

No oral vibrissae. ......... 45

44. Mesonotum and scutellum flat; front bristly; cheeks and face bris-

tly; all the tibiae spurred and with preapical bristle; seashore

flies. . PhycodromidsB, 317

Mesonotum not flattened, convex; no costal spine; more than
four abdominal segments visible. . Cordyluridae, 327


Wings elongate, the cross-veins often approximated; post-vertical
bristles divergent; front bristly; smaller, somewhat elongate
flies; sixth and first veins short. . Heteroneuridae, 318

Front never bristly near the antennae; abdomen somewhat elon-
gate, cylindrical, usually narrowed near base. Small, black
flies about decaying matter Sepsidse, 269

Costa almost always pectinate; tibiae with spurs and preapical
bristles; not very small flies. . . Helomyzidse, 324

45. Femora thickened; hind tibiae usually dilated; basal cells not very

small; first posterior cell narrowed; all the tibiae with preapical
bristle. Moderate sized, bare, southern flies.

Rhopalomeridse, 280
Not such flies. ......... 46

46. First posterior cell closed or narrowed in the margin; abdomen

elongate; legs long or very long 47

Not such flies. ......... 48

47. Kyes large, the cheeks and posterior orbits narrow, the occiput


Proboscis short; ovipositor not elongate. Tanypezidse, 264
Proboscis greatly elongate and folding near its middle; ovipos-
itor very long Conopidge, pt. 261

Head subspherical, the cheeks broad and face retreating; probos-
cis short Micropezidae, 264

48. One or two fronto-orbital bristles; preapical bristle absent or pres-

ent; wings sometimes pictured; anal cell always rounded distally.

Sapromyzidse, 288

Upper fronto-orbital bristles, only, present; ovipositor horny, more
or less elongate; anal cell often acute distally, or drawn out
into a narrow, acute lobe; arista seldom plumose; no preapical
bristle (except Autoniola) ; wings almost invariably pictured.

Ortalididse, 272

Fronto-orbital bristles present* or absent; second joint of antennae
often elongated; postvertical bristles divergent; a preapical
bristle; ovipositor not horny; wings often pictured. Meadow
flies. Sciomyzidae, 321

49. Head produced on each side into a lateral process for the eye;

basal cell confluent with discal cell. . . Diopsidse, 314
Head not produced into lateral processes 50

* If small, greenish black flies of the sea-coast, with globular third
antennal'joint, compare Canace (Kphydridae).


50. Hind metatarsi incrassate and usually shorter than the second

joint; oral vibrissse present; second basal cell distinct or not;

Online LibrarySamuel Wendell WillistonManual of North American Diptera → online text (page 5 of 25)