Cleptoparasitism of Tachysphex terminatus (Hymenoptera: Sphecidae) by Three Species of Miltogrammini (Diptera: Sarcophagidae)

Abstract

Three species of miltogrammine flies utilized various phases of the nesting sequence of Tachysphex terminatus (Smith) for parasitic larviposition at two sites in central New York. Phrosinella aurifacies Downes larviposited primarily in temporarily closed wasp entrances. Senotainia vigilans Allen maintained surveillance perches near entrances during the wasp's burrow construction and hunting forays and larviposited on the prey when the wasp was preoccupied with provisioning activities. S. trilineata (Van der Wulp) was attracted by the wasp's provisioning flight and attacked the prey in midair or on the ground, larvipositing almost always in the presence of the wasp. T. terminatus attempted to prevent larviposition by the flies or, if larviposition occurred, to remove maggots from the prey using the mandibles. These attempts included face-offs, chases, and diversionary flights. The difference in the frequencies of cleptoparasitism at Auburn (57.9%) and Chittenango (30.6%) reflected the effectiveness of maggot removal by T. terminatus and the species of cleptoparasite. S. vigilans, the predominant cleptoparasite at Auburn (32.9% mortality), usually larviposited when the wasp was out of sight and was more successful than S. trilineata at Chittenango (12.2% mortality). P. aurifacies accounted for ca. 20% of the miltogrammine cleptoparasitism at both sites. The two generations of wasps each summer were afflicted by the same amount of parasitism.