ii. Species of a stouter build; third segment of the antenna stout, its basal process short (fig. 161b). Many species, widely distributed TABANUS L. dd. With another group of characters. e. Squamæ small, antennæ variable, thinly pilose or nearly bare species, without distinct bristles; wing veins not crowded anteriorly, R_4 and R_5 both present, basal cells large; middle tibiæ at least with spurs. LEPTIDÆ 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. 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. STRATIOMYIIDÆ, CYRTIDÆ, etc. cc. Empodium bristlelike or absent. d. Antennæ apparently two segmented, with three-segmented arista, wings (rarely wanting) with several stout veins anteriorly, the weaker ones running obliquely across the wing (fig. 163h); small, quick running, bristly, humpbacked flies. Several genera; APHIOCHÆTA, PHORA, TRINEURA, etc. PHORIDÆ dd. Flies with other characters.