The natural history of a miltogrammine fly, Miltogramma rectangularis (Diptera : Sarcophagidae)

The miltogrammine fly, Miltogramma rectangularis. is a common and widesprea d brood parasite of the large Australian native bee, Amegilla dawsoni. Rece ntly eclosed flies emerged from the underground brood cells of the bee and walked rapidly across bare ground to reach cover in the vegetated fringe of the nesting area. While walking, the flightless flies were vulnerable to b ird and ant predators. but they may have minimized their exposure by mainta ining a constant compass orientation until a perch was found. Once perched inconspicuously, the dies spent about an hour inflating and hardening their wings before they were able to Ay. At some sites, males located, courted, and mated teneral females in a scramble competition mating system. Although hundreds of flies emerged from parts of some nesting areas over several we eks, adult females seeking to larviposit on passing bees were generally sca rce. The proportion of brood cells lost to the parasite was low (under 5%). As a result, it seems unlikely that parasite pressure by the fly contribut es greatly to the male size dimorphism that characterizes A. dawsoni, becau se even if brood provisions intended for large sons were at greater risk of exploitation by the parasite, the percentage lost would still be too small to outweigh the great mating advantage experienced by the larger males.