DIPTERA. 461 



tip. The antennae project forward in a prominent manner. 

 They are three-jointed, and with or without a terminal style. 

 The style when present sometimes appears like one or two 

 additional segments (Fig. 558). 



Vein III 4 (Fig. 559) does not curve forward toward the 

 costal margin of the wing as in the following family. Cell 

 V 3 is present, but is usually closed by the coalescence of the 



FIG. 559. Wing of Erax. 



tips of veins V 3 and VII,. The tips of veins VII., and IX 

 may or may not coalesce for a short distance. The robber- 

 flies are extremely predaceous. 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. 



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

 where they prey upon the larvae of beetles ; some, however, 

 are supposed to feed upon the roots of plants. The pupae 

 are free. 



The family includes a large number of genera and 

 species. 



Family MlDAlDyE (Mi-da'i-dae). 

 The Midas-flies. 



The Midas-flies rival the robber-flies in size, and quite 

 closely resemble them in appearance. As in that family, 

 the vertex of the head is hollowed out between the 



