COMPARISONS AND CONTRASTS IN HOST-FORAGING STRATEGIES OF 2 LARVAL PARASITOIDS WITH DIFFERENT DEGREES OF HOST-SPECIFICITY

In theory, the degree of specificity of the signals a parasitoid speci es needs to successfully locate its host correlates with its level of specialization. We examined this question by comparing the foraging st rategies of two parasitoids that differ in their host ranges. In wind- tunnel experiments, we investigated how systemically released herbivor e-induced volatiles were used by the generalist parasitoid, Cotesia ma rginiventris (Cresson) and the specialist, Microplitis croceipes (Cres son). We determined the relative influence of these volatiles as compa red to other signals emitted in the host orientation of the two parasi toids. Both the generalist and the specialist parasitoid strongly pref erred Spodoptera exigua (Hubner) leaf-induced systemic plants over und amaged plants when no other information was available. When wasps were given a choice between leaf-induced and undamaged plants carrying oth er plant- or host-related materials, the responses differed for the tw o species. C. marginiventris appeared to cue primarily on recent damag e volatiles, whereas M. croceipes appeared to cue primarily on host fr ass volatiles. However, recent damage on previously leaf-induced plant s, was strongly preferred to recent damage on plants previously damage d by both species. When plants were induced at the squares by Helicove rpa tea (Boddie), only M. croceipes exhibited a preference for these p lants over undamaged plants. The adaptive significance of the behavior s as related to dietary specializations of the parasitoids is discusse d.