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. 136
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