252 



CALIFORNIA ACADEMY OF SCIENCES [Proc. 4th Sm. 



299. Rhabdopselaphus sigma (Coq.) 

 Dee, VI- 17 (Cole). 



300. Toxophora maxima Coq. 

 Hood River, VI-13 to IX-4 (Cole). 



Family ASILID^ 



Fig. 22. Cyrtopogon thompsoni Cole, n. sp. Drawing of holotype. 



The robber-flies vary in size from one-third of an inch to 

 two inches in length. A few are bright colored, but the 

 majority of the species are sober gray with black markings. 

 The head is short, the eyes widely separated in both sexes 

 and bulging out; the body is more or less bristly in all the 

 species. 



These flies are very savage and catch much of their prey 

 in mid-air, even killing other asilids. Wasps, moths and 

 even large grasshoppers are pounced upon, the choice of the 

 victims depending upon the size of the brigand. Certain 

 genera seem to prey on certain orders of insects. The larvae 

 are generally beneficial, as probably all prey upon other 

 insect larvae, either in the ground or in rotten wood. 



