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742 COLLEGE ENTOMOLOGY
38. Anal cell elongate, tapering and acute apically, closed near the border
of the wing; basal cells usually elongate . 39
Anal cell short, transverse, oblique, or convex apically, if somewhat
pointed the apex partly transverse, partly drawn out into a tri·
angular point posteriorly . . 40
39. Anal cell closed very close to the wing margin; a spurious vein run·
ning obliquely between the third and fourth longitudinal veins.
(Syrphid Flies, Flower Flies.) . SYRPHIDlE p. 781
Anal cell usually shorter; no spurious vein . 40
40. Head extremely large, hemispherical, the front and face very narrow,
arista dorsal. (Big·headed Flies.) . PIPUNCULID./E p. 785
Head not unusually large, face or front usually wide • . 41
41. Frontal lunule entirely absent, the parafacials not differentiated by
a suture . , . 42
Frontal lunule present, parafacials differentiated by a suture which
extends above the antennre and is indistinct only in some
CONOPlDlE 44
42. Anterior cross vein situated at or before the basal fourth of the wing;
second basal and discal cells always united. (Long·legged Flies.
Long·headed Flies.) . . DOLICHOPODID.1E p. 776
Anterior cross vein situated far beyond the basal fourth of the wing
or the second basal cell complete . 43
43. Anal cell pointed posteriorly; proboscis never rigid and adapted for
piercing. (Flat-footed Flies.) PLATYPEZIDJE p. 780
Anal cell not pointed posteriorly; proboscis usually rigid; never a single
row of acrostical hairs. (Dance Flies.) , EMPIDID.1E p. 775
44. Coxre close together at the base, the legs attached ventrally ,45
Coxre widely separated at the base, the legs attached towards the sides
of the thorax; usually leathery or coriaceous flies; ectoparasites
(PUPIPARA) 91
45. Second antenna! segment with a longitudinal seam along the upper
outer edge extending almost the whole length; postedor calli definitely
formed by a depression extending from behind the base of
the wings to above the base of the scutellum
(CALYPTRATtE; MUSCOIDEA) 85
Second antennal segment rarely with a well-developed dorsal seam,
the postedor calli not differentiated (except in Gasterophilus);
squamre small . (ACAL YPTRAT lE) 46
46. Mouth parts vestigial, sunken in a very small oral pit. (Gadflies,
Horse Botflies.) . , , , . . . GASTEROPHILIDlE p.802
Mouth parts wen developed, the oral opening large . . 47
47. Posterior spiracle with several hairs on the border in addition to the
pubescence (visible only with high magnification) , 50
Posterior spiracle with pubescence only. . . . . . . . 48
48. Subcosta complete, free from the first vein and ending in the costa
(cI. TRYPETIDIE), . . . . . . . . . . . . 64
Subcosta incomplete, or not ending in the costa, or the apex curved
forwards beyond the bend . . . . . , . . . . . 49
49. Subcosta curved forwards at nearly a right angle and weakened beyond