f. Flagellum of the antenna more or less elongated, composed of numerous more or less distinct divisions. Xylophaginæ and Arthroceratinæ.
ff. Antennæ short, third segment simple, with arista or style; face small, proboscis short Leptinæ
g. Front tibiæ each with one or two spurs, or if absent, then no discal cell. Triptotricha, Pheneus, Dialysis, Hilarimorpha.
gg. Front tibiæ without terminal spurs, discal cell present.
h. Hind tibiæ each with a single spur.
i. Anal cell open ([fig. 163g]); 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 tibiæ 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.