A Test of Local Mate Competition Theory with a Solitary Species of Parasitoid Wasp, Spalangia Cameroni

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Abstract
The effect of conspecific females on offspring sex ratio was examined in the parasitoid wasp Spalangia cameroni. In the presence of a second female, females increased the proportion of sons they produced relative to when they were alone, as predicted by local mate competition theory. However, females did not seem to differentiate between two and more than two females: offspring sex ratios from groups of two, four, six, and ten females were not significantly different. The trace odor of another female was not a sufficient cue for females to increase the proportion of sons they produced. Results indicate that for species with large interfemale variation in offspring sex ratio, it is preferable to test how the presence of other females affects offspring sex ratio by looking for changes within individual females rather than by comparing different-sized groups of females.