Diptera 
295 
g. Front tibiae each with one or two spurs, or if absent, then no 
discal cell. Triptotricha, Pheneus, Dialysis, Hilarimorpha. 
gg. Front tibae without terminal spurs, discal cell present, 
h. Hind tibae each with a single spur. 
i. Anal cell open (fig. i63g); third antennal segment kidney¬ 
shaped with dorsal or subdorsal arista; first antennal 
segment elongate and thickened. About a dozen species 
have been described from the United States, of which at 
least one (S. pachyceras) is knowm to be a vicious blood 
sucker.Symphoromyia Frauenf. 
ii. Anal cell closed; third antennal segment not kidney¬ 
shaped. Chrysopila, Ptiolina, Spania. 
hh. Hind tibiae each with two spurs. 
i. Third segment kidney-shaped, the arista subdorsal; anal 
cell closed. Atherix Meig. 
ii. Third segment of the antenna short and with terminal 
arista; anal cell open. Leptis Fabr. 
Two European species of this genus have been accused of 
blood sucking habits, but the record seems to have 
been based upon error in observation. 
ee. With another combination of characters . 
. Stratiomyiid^e, Cyrtid^e, etc. 
cc. Empodium bristlelike or absent. 
d. Antennae apparently two-segmented, with three-segmented arista, 
wings (rarely wanting) with several stout veins anteriorly, the 
weaker ones running obliquely across the wing (fig. 163I1); small, 
quick running, bristly, humpbacked flies. Several genera; Aphio- 
chaeta, Phora, Trineura, etc. Phorid.® 
dd. Flies with other characters. 
e. No frontal lunule above the base of the antennae; both R4 and R5 
often present; third segment of the antenna often with a terminal 
bristle. AsiLlDiE, Mydaid.e, Apiocerid.e, Therevid^e, Sceno- 
PIMD.E, Bombyliid/E, Empidid^;, Dolichopodid.e, Lonchop- 
TERID.E. 
ee. A frontal lunule above the base of the antennae; third segment of the 
antenna always simple, i.e., not ringed, usually with a dorsal 
arista; R4 and R5 coalesced into a simple vein, 
f. A spurious vein or fold between the radius and the media, rarely 
absent; the cell R4+5 closed at the apex by vein Mi; few or no 
bristles on the body, none on the head; flies frequently with 
yellow markings. Eristalis (fig. i63i), Helophilus, and many 
other genera . SyrphiDjE 
ff. No spurious vein present. 
g. Body without bristles; proboscis elongate and slender, often 
folding; front of both male and" female broad. . . . Conopid/E 
gg. Bristles almost always present on head, thorax, abdomen and 
legs. 
