DIPTERA 



841 



form. This resemblance is often increased by a dense clothing of 

 black and yellow hairs. 



In this and the following family the vertex of the head is hollowed 

 out between the eyes (Fig. 1087). In this family the proboscis is 

 pointed and does not bear fleshy lips at the tip. The antennae project 

 forward in a prominent manner. They are three-jointed, and with or 



Fig. 1086. — Erax api- 

 calis destroying a 

 cotton worm. 



Fig. 1088. 



Fig. 1087. — Head of 

 a robber-flv. 



without a terminal style. The style when present sometimes appears 

 like one or two additional segments (Fig. 1088). 



Vein Ml (Fig. 1089) does not terminate at or before the apex of 

 the wing as in the following family. Cell M3 is present, but is usually 

 closed by the coalescence of the tips of veins M3 and Cui. The tips 

 of veins Cu2 and 2d A may or may not coalesce for a short distance. 



The robber-flies are extremely predacious. They not only destroy 

 other flies, but powerful insects, as bumblebees, tiger-beetles, and 

 dragon-flies, fall prey to them; they will also feed upon larvae. They 

 are common in open fields and are as apt to alight on the ground as on 

 elevated objects. 



Fig. i( 



-Wing of Erax. 



The larvce live chiefly in the ground or in decaying wood, where 

 they prey upon the larvae of beetles; some, however, are supposed to 

 teed upon the roots of plants. The pupae are free. 



More than five hundred North American species of this family, 

 representing seventy-five genera, have been described. 



