Host Mortality and Progeny Production by Solitary and Gregarious Parasitoids (Hymenoptera: Pteromalidae) Attacking <I>Musca domestica</I> and <I>Stomoxys calcitrans</I> (Diptera: Muscidae) at Varying Host Densities

Abstract

Relationships between host density and mortality of house fly, Musca domestica L., and stable fly, Stomoxys calcitrans (L.), caused by Muscidifurax raptor Girault & Sanders, Muscidifurax zaraptor Kogan & Legner, Muscidifurax raptorellus Kogan & Legner, and Trichomalopsis sarcophagae Gahan were determined. Host mortality varied with host density and was highest when pupae were exposed to M. zaraptor followed by M. raptor, M. raptorellus, and T. sarcophagae. The relationship between host density and mortality was unaffected by host species for M. raptor and M. zaraptor; however, M. raptorellus killed a higher percentage of stable fly pupae and T. sarcophagae killed a higher percentage of house fly pupae. Residual mortality was higher on stable fly pupae than house fly pupae for M. zaraptor and M. raptorellus. The percentage of pupae with parasitoid emergence was reduced on stable fly pupae only for M. zaraptorand T. sarcophagae compared with house fly pupae. The gregarious species M. raptorellus and T. sarcophagae superparasitized pupae at low host densities and produced high numbers of progeny per female even at low host densities. Progeny production by T. sarcophagae was low on stable fly pupae compared with house fly pupae. The proportion female showed either no change or a small increase as host density increased for Muscidifurax species; however, T. sarcophagae had a greatly reduced proportion female at low host densities on house fly pupae. The number of female progeny per female parasitoid increased with host density for all parasitoid species except for T. sarcophagae parasitizing stable fly pupae. The reduced sex ratio of T. sarcophagae and low host mortality at low host densities suggested this species offers no advantage in terms of rearing efficiency, whereas the Muscidifurax species would be more efficient for rearing and release.