68 NORTH AMERICAN DIPTERA. 



41. Throe submarginal cells. . , " 42 



Two submarginal cells. . . . - . GKRON Meigen. 



42. Body clothed with more scales than hairs; abdomen decumbent ; an- 



tennae long. TOXOPHORA Meigen. 



Body clothed chiefly with hair ; abdomen not decumbent. 



RHABDOPSELAPHUS Bigot. 



22. THEREVIM:. 



Rather small or moderate sized, elongate, bristly, sometimes 

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

 in the female not excavated. Antennae composed of three 

 joints, the third simple, with a terminal style, sometimes 

 wanting. Proboscis projecting, 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 beyond 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 Asilidse somewhat, and have habits 

 not dissimilar, though much less active. The proboscis has 

 fleshy labella, instead of the horny tip of the Asilidse, 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 larvae have a short, eyeless, nonretractile head, 

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

 like, showing apparently nineteen segments. Anterior spira- 

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

 posterior spiracles on the apparently seventeenth segment. 

 The larvae live in the earth arid decomposing wood, or in sand, 

 feeding upon other insects or upon vegetable matter, ordure, 

 etc. The pupae are free; they have in front laterally project- 

 ing spinous points. 



