The link between host density and egg production in a parasitoid insect: comparison between agricultural and natural habitats

1. Theory predicts that organisms should invest in overcoming a factor that may limit their reproductive success in direct proportion to their probability of being limited by it. The occurrence of egg limitation (where female insects deplete their eggs while oviposition opportunities are still available) is predicted to impose selection for increased fecundity at the expense of other fitness components. 2. We tested the hypothesis that the fecundity of a proovigenic parasitoid (where females emerge with their full egg load) should be positively correlated with the mean expectation for oviposition opportunities in the environment. More specifically, we tested whether females from agricultural systems, where hosts are often relatively abundant, emerge with more eggs than those from natural habitats. 3. We studied the proovigenic parasitoid wasp Anagrus daanei, which parasitizes eggs of leafhoppers of the genus Erythroneura. Erythroneura spp. leafhoppers feed on Vitis spp. (grapes) and are...