ROBBERFLIES OF THE GENUS ASILUS.* 



James S. Hine. 



The insects of this genus together with a large number of 

 others belong to the Asilidae which is a family of Diptera com- 

 monly called robberflies because of their predaceous habits in 

 the adult stage. These habits usually lead to beneficial results but 

 none of the species are known to show any indication that they 

 prefer particular food. They take all kinds of insects that inhabit 

 like places with them, and have the habit of alighting on a leaf 

 or a stone, a log or other object, or even on the bare ground to 

 wait for some unfortunate insect of almost any order to appear, 

 when they leave their perch and, like a hawk, pounce upon the 

 chosen victim and at once introduce their piercing mouthparts 

 and suck away its life blood. Occasionally some observer finds 

 certain species to be injurious on account of feeding on beneficial 

 species, and it is no more than likely that all of the members of 

 the family do some harm. Riley has stated that one of the larger 

 robberflies may be very destructive to honey bees, and frequently 

 one may see one or another of the f^ies with a parasitic insect in 

 possession. Such habits furnish much of interest to the observer 

 in the field, and the student who is in search of a subject full of 

 sentiment will do w^ell in making a selection here. 



So far as known the larvae are predaceous and are found in" 

 dry ground. They work beneath the surface and seek out such 

 available food as these situations offer. Two larvae of Asilus 

 sericeus Say, were taken April 3, while spading a garden. They 

 were located about six inches below the surface of the ground, 

 color white, naked with the exception of a very few brown hairs 

 scattered over the body, general form cylindrical, or only slightly 

 compressed ; in appearance much like what in general pass under 

 the common name of grubs. Total length when full grown 20 

 millimeters. The pupa stage w^as reached May 25, and the adult 

 appeared June 8. 



The various species of the family are mostly large insects, but 

 have been neglected more or less in America, some of the genera 

 as yet not having received the attention of specialists beyond the 



* Contributions from the Department of Zoology and Entomology of the 

 Ohio State University, No. 32. 



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