3 io THE STUDY OF INSECTS 



not bear fleshy lips at the tip. The antennas are three-jointed, and with 

 or without a terminal style. 



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 com- 

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

 objects. 



The larvae live chiefly in the ground or in decaying wood, where they 

 prey upon the larvae of other insects; some, however, are supposed to 

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



More than five hundred North American species of this family, repre- 

 senting seventy-five genera, have been described. 



Family Mydaid^e 



The Mydas-flies 



The mydas-flies rival the robber-flies in size, and quite closely re- 

 semble them in appearance. As in that family, the vertex of the 

 head is hollowed out between the eyes; but these flies can be dis- 

 tinguished by the form of the proboscis, which bears a pair of fleshy 

 lobes at the tip, by the form of the antennae, which are four- 

 jointed, long and more or less clubbed at the tip (Fig. 548) and 

 by the peculiar venation of the wings (Fig. 549). 



The adults are said to be predacious. The larvae of some spe- 

 cies, at least, live in decaying wood, and some are known to prey 

 upon the larvae of beetles. 

 fig^548. The family is a small one; but it includes the largest flies 

 in the Diptera. 



M+. 



M^Cut 



Cut+zd A 



Fig. 549- — Wing of Mydas. 



Family Dolichopodid^e 

 The Long-legged Flies 



These flies are of small or medium size and usually bright metallic 

 green or blue in color. The legs are much longer than is usual in the 

 related families but not as long of course as in the crane-flies. The family 

 is a very large one. 



The members of this family are easily distinguished as such by the 

 peculiar venation of the wings (Fig. 550). 



