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 known 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. 16311); 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 RS 

 often present; third segment of the antenna often with a terminal 

 bristle. ASILID.E, MYDAID^:, APIOCERID^, THEREVID^, SCENO- 



PINID.E, BOMBYLIHLE, 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 RS 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. 163*), 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^s 

 gg. Bristles almost always present on head, thorax, abdomen and 

 legs. 



