344 



AX ECOXOMIC EXTOMOLOGY. 



their resemblance to, and to distinguish them from, the " horse- 

 flies." 



Another series of large species we find among the "robber- 

 flies" belonging to the family AsilidcB, and these are quite 

 different in appearance from any heretofore treated. The head is 

 prominent, very hairy, with rather short, several-jointed antennae, 



and with a short, stout proboscis. 

 Fig. 393. which is formed for piercing. The 



body is robust, also covered with hair, 

 and the abdomen is long, slender, and 

 cylindrical, tapering very gradually to 

 the tip. The wings are long and nar- 

 row, the legs moderately long and very 

 powerful, densely clothed with spines, 

 while the tips of the tarsi are supplied 

 with unusually long and stout claws. 

 The insects are called ' ' robber-flies' ' 

 from their habit of pouncing^ upon, 



An Asilid fiy.—Erax bastardi, . . . . . . .. ^ . 



larva, pupa, and adult. picrcmg, and suckmg the juices ot 

 other insects in mid-air, while holding 

 them with their powerful legs. We have a great varietv of 

 species, some of them large and brightly colored, though the 

 majority are of a sober gray, varying sometimes to reddish, 

 sometimes to yellow, and only rarely becoming black, except in 

 the genus Laphria. Though predaceous, the insects can hardly 

 be called beneficial, because they rarely attack injurious species, 

 and in some cases become themselves injurious by attacking 

 bees. The late Dr. C. V. Riley records having obser^-ed a single 

 species kill forty bees in one afternoon. Professor Comstock 

 notes their feeding upon the cotton-worm, and undoubtedly 

 they do occasionally kill injurious insects, but can scarcely be 

 credited with being a factor of much importance in keeping down 

 troublesome forms. They never attack man or animals, although, 

 if carelessly handled, they are ready to sink their lancets into the 

 flesh of their captor. The lar\'ae are also carnivorous, so far as 

 known, and live in the ground or in decaying wood. 



Yet larger in size and of the same general shape are the mem- 

 bers of the family MidaidcB. They are often contrastingly col- 

 ored, sometimes uniformly dead black or blue, though usually 



