Offspring size-number strategy in the bethylid parasitoid Laelius pedatus

I observed clutch size and body size of resulting offspring for the parasitoid Laelies pedatus (Say) (Hymenoptera: Bethylidae) on hosts of different sizes. Results were compared with the predictions of offspring size-number models and clutch-size models. Larger clutches were laid on larger hosts. However, even after females had adjusted dutch size to the size of the host, offspring size was larger in larger broods. The variance in offspring size between broods decreased with increasing dutch size as expected, but the decrease was smaller than predicted by Charaov and Downhower's trade-off invariant rule. Theory predicts such trends when the shape of the trade-off between per capita investment and per capita offspring fitness depends on dutch size or host size. By observing how this assumption might apply to bethylid wasps, I generate a number of testable hypotheses to explain the observed trends.