PROC. ENTOMOL. SOC. WASH. 81(3), 1979, pp. 366-378 ETHOLOGY OF HOLCOCEPHALA FUSCA IN VIRGINIA (DIPTERA: ASILIDAE) D. Steve Dennis* 5875 E. Weaver Circle, Englewood, Colorado 80111. Abstract.— Holcocephala fusca Bromley foraged primarily from twig tips on the edges of forest clearings. Prey were captured and immobilized in flight. The preferred prey consisted of Hymenoptera and Diptera. While in copula the male assumed a position similar to that observed in Leptogaster spp., with his head down and dorsal surface facing the same way as the female's ventral surface. Collected eggs had hexagonal sculpturing on the chorion. Grooming behavior and nocturnal resting position are similar to that described for other species of Asilidae. In the United States there are three described species in the robber fly genus Holcocephala (Martin, 1965): H. abdominalis (Say), H. calva (Loew), and H. fusca Bromley. To date only the ethology of//, abdominalis has been described in some detail (Johnson, 1976) and limited ecological observations have been made for the other two species. The present paper adds to our knowledge of the ethology and ecology of H. fusca. This species was studied intermittently for a two week period from August 21 to September 5, 1976, in a forested area in Fairfax, Virginia, at an elevation of approximately 152 m above sea level. The habitat con-sisted of a mixed stand of pine (Pinus sp.), oak {Quercus sp.) and a few hickory {Carya sp.) trees, with a dense shrub understory of blackberry (Rubus sp.), greenbrier {Smilax sp.), and rose {Rosa sp.). Holcocephala fusca were mostly found on the edge of the forested area near its juncture with lawn areas of apartment buildings. A few asilids were also observed on the edge of small clearings in the forest, but they seemed to prefer and were most abundant near large, open areas. This species was never ob-served in the darker more thickly vegetated areas of the forest. Both H. abdominalis and H. calva have generally been reported to occur in moist edges of meadows, woodland areas and marshy lakes which contain sedges ' Ecologist, Environmental Sciences Division, Stearns-Roger Incorporated, P.O. Box Denver, Colorado 80217.
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