Larval Competition Among Three Hymenopterous Parasite Species on Multiparasitized Housefly (Diptera) Pupae

Only one parasite species survived on most housefly (Musca domesticaL.) pupae multiparasitized by any two ofNasonia vitripennis(Walk.),Muscidifurax zaraptorK. & L., orSpalangia cameroniPerk.N.vitripennisandM.zaraptorwere both intrinsically superior toS.cameroniif the attacks on the hosts by their females preceded, were simultaneous with, or followed by up to 48 hours those by females ofS.cameroni.N.vitripenniswas intrinsically superior toM.zaraptorif its attack preceded that byM.zaraptorby at least 24 hours;M.zaraptorsurvived when it oviposited beforeN.vitripennis; and neither species was consistently superior to the other when their attacks were simultaneous or that byN.vitripennisclosely preceded that byM.zaraptor.N.vitripennisoften survived on multiparasitized hosts because of its rapid development and rapid and thorough host utilization which caused its rivals to starve. In contrast,M.zaraptor’ssuccess was a consequence of its prédation on eggs and larvae of its competitors and to a lesser extent its moderately rapid development and host utilization.S.cameroniwas usually intrinsically inferior to both of the other species because, in spite of being predaceous on their larvae, it developed much more slowly and seldom attacked their eggs. The significance of these qualitative characteristics in insect parasites used in biological control programmes is discussed.