Variable host quality, life-history invariants, and the reproductive strategy of a parasitoid wasp that produces single sex clutches

The parasitic wasp Achrysocharoides zwoelferi (Hymenoptera, Eulophidae) pro duces clutches consisting of only one sex. Moreover, male clutch size is in variably one while female clutches are in the range one to four. We designe d field experiments to determine the effect of host quality on clutch compo sition. We found that solitary male and solitary female clutches were reare d from the same size mines, and that larger mines tended to produce gregari ous female clutches. A higher proportion of male clutches were placed in ol der hosts, despite their large size. Variation in body size, both between a nd within clutches, was measured in order to test the predictions of models that take into account the constraint that clutch size is an integer trait , something of potential importance when absolute clutch size is low. Our d ata supported several predictions of these models, including the trade-off- invariant rule for optimal offspring size developed by Charnov and Downhowe r. However, while most invertebrate clutch size models assume equal resourc e share among members of the same clutch, we found an increase in inequalit y in larger clutches.