Spalangia cameroni is a small wasp which lays its eggs in the pupal stage of house flies. This research focuses on the ability of female S. cameroni to manipulate the offspring sex ratios (the proportion of sons) they produce in response to the size of the host (fly) in which the offspring is laid. Females lay a greater proportion of sons on small hosts than on large hosts. An effect of host size on wasp offspring sex ratios has now been found in more than forty species of parasitoid wasps in thirteen different families. This research will address two areas for which there is currently very little information: how manipulation of sex ratio in response to host size affects a mother's success at reproducing and how mothers assess host size. Species of Spalangia have been released in poultry houses and stables to control pest flies, especially house flies. Use of such "biological controls" is becoming increasingly important as the flies become resistant to more and more insecticides. Research on sex ratios is important in terms of being able successfully to rear large numbers of wasps for release.
