PROC. ENTOMOL. SOC. WASH. 83(2). 1981. pp. 258-268 ETHOLOGY OF EUDIOCTRIA TIBIALIS BANKS (DIPTERA: ASILIDAE) IN MARYLAND: PREY, PREDATOR BEHAVIOR, AND ENEMIES A. G. SCARBROUGH Professor of Biology, Department of Biological Sciences/Institute of An-imal Behavior, Towson State University, Baltimore, Maryland 21204. Abstract. — Eiidioctria tibialis Banks foraged under bright skies from dim-ly lit or sunlit perches at temperatures above 16°C. Grooming, prey manip-ulation, feeding time prey prey, and foraging activities are discussed. Major prey were aphids and lower Diptera, although Isoptera or other insects were taken in large numbers when abundant. Most prey had thin cuticles and were weak fliers. Mean prey size was 3.02 mm. Females selected slightly larger prey than males. A list of prey is given. Vespula maciilata (L.) may be an important predator of Eiidioctria tibialis under certain conditions. At the present time behavioral and ecological information on species of the genus Eiidioctria, as well as most Asilidae, is limited. Scarbrough (1981) recently reported the seasonal distribution, abundance, and diurnal activi-ties of a population of Eudioctria tibialis Banks in Maryland. Some biolog-ical information of several European species of Dioctria was contributed by Melin (1923) and Poulton (1906). However neither critically examined prey selection, but both concluded that Dioctria spp. selected primarily hymen-opterous prey. The purpose of this study was to report on predator behavior and prey selection of E. tibialis and its enemies. Methods General methods and location of the study site were described previously (Scarbrough, 1981). Data on predator behavior were obtained by censusing individuals at the study site and by following individual flies for extended periods. Hourly observations were made during the fly season to determine maximum variability in behavior patterns of predators and in the selection of prey types. During each census, flies were recorded as feeding or involved in other behaviors. Individual flies were observed in order to obtain infor-mation of foraging, feeding and manipulation behaviors. Prey were obtained by capturing feeding flies in a 15 dram snap top plastic vial, with the predator
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