Offspring Sex Ratio and Number in Response to Proportion of Host Sizes and Ages in the Parasitoid Wasp Spalangia cameroni (Hymenoptera: Pteromalidae)

In rearing parasitoids for biological control releases and in natural populations, female parasitoids may encounter variable distributions of host quality. Here I examine how the proportion of hosts that are small versus large or old versus young affects sex ratio and offspring production of the parasitoidwasp Spalangia cameroniPerkins parasitizingMuscadomesticaL. pupae.With increasing proportion of small hosts or old hosts, overall number of offspring did not signiÞcantly decrease and the overall proportion that weremale (i.e., from small and large hosts combined) did not signiÞcantly increase. A greater proportion of sons from small versus large and from old versus young hosts was not restricted to the case of equal numbers of different host types. The proportion of sons produced from small hosts as well as the proportion of sons from large hosts decreased as the proportion of small hosts increased, and the proportion of sons produced from young hosts decreased as the proportion of old hosts increased. These results are relevant to recommendations for rearing S. cameroni for biological control releases and to testing evolutionary sex ratio theory, speciÞcally a combined host-quality and local mate competition model.