Host age preference of the pupal parasitoid, Spalangia Cameroni (Hymenoptera: Pteromalidae)

The house fly, Musca domestica L., is a cosmopolitan nuisance pest implicated as a vector of human and animal pathogens and a source of economic detriment for the animal agriculture industry. Although managed with insecticides, house fly resistance evolution has resulted in product failure. Therefore, continued research to improve the effectiveness of alternative filth fly management strategies, such as releasing hymenopteran pupal parasitoids as biological control organisms, is necessary. The pupal parasitoid, Spalangia cameroni Perkins, naturally occurs in and around livestock and poultry facilities, and is a commercially available species that can be purchased to supplement on-site populations. Previous research with S. cameroni has assessed its preference for various hosts- and host-occupied substrates, the influence of host age on host selection and subsequent parasitoid sex ratio, and dispersal from release sites. However, the effect of host age on S. cameroni parasitism rates is largely unknown. A study was conducted to determine if house fly host age effects S. cameroni parasitism rates. Parasitoids were confined indefinitely with hosts ranging in age from the egg to adult or were confined for 24 hours with hosts that ranged from pupae on the day of their formation to the adult stage. Parasitism rates were highest when parasitoids were provided pupae aged < 4 days old. This finding was consistent among parasitoids confined indefinitely with prepupal hosts, which were forced to wait for house flies to develop into pupae that were appropriately aged. Additional findings and their implications will be further discussed.