68 XORTPI AMERICAN DIPTEKA. 



41. Three sul)niart;inal cells. ........ 42 



Two siibinarginal cells. . . . - . Gkron Meigen. 



42. Body clotiicd witli more scales than hairs; al)(lonieii decumbent ; an- 



tennte lon<r. ...... Toxopiiora Meigen. 



Body clotlied chiefly with hair ; abdomen not decumbent. 



RHABDOPSELAPUrS Bjoot. 



22. THEREVID^. 



Rather small or moderate sized, elongate, bristly, sometimes 

 pilose, predaeeous flies. Eyes of the male contiguous ; front 

 in the female not excavated. Antennae composed of three 

 joints, the tlurd sim])le, with a terminal style, sometimes 

 wanting. Prol)oscis ])r()jecting, the labella broad. Ocelli 

 present. Abdomen elongate ; genitalia moderately or but lit- 

 tle prominent. Legs with bristles ; empodia wanting. Third 

 longitudinal vein of the wings furcate, the posterior branch 

 terminating bej^ond the tip of the wing; five posterior cells, 

 anal cell closed toward the margin of the wing. 



This family comprises only about two hundred known spe- 

 cies, with but few genera broadly distributed over the world. 

 The flies resemble the Asilida? somewhat, and have habits 

 not dissimilar, though much less active. The proboscis has 

 fleshy labella, instead of the horny tip of the Asilida?, and the 

 legs are less stout — in many species they are easily broken off 

 when captured. Their food is chiefly other diptera, for which 

 they lie in wait upon leaves and bushes, or upon the bare 

 ground. The larvte have a short, eyeless, nonretractile head, 

 the antenufe small and short. The body is slender and snake- 

 like, showing apparently nineteen segments. Anterior spira- 

 cles situated at the end of the flrst segment behind the head ; 

 posterior spiracles on the apparently seventeenth segment. 

 The larvce live in the earth and decomposing wood, or in sand, 

 feeding upon other insects or upon vegetable matter, ordure, 

 etc. The pup,-© are free; they have in front laterally ])roiect- 

 ing S])inous ])oints. 



