Effects of origin and experience on patterns of host acceptance by the opiine parasitoid Diachasmimorpha tryoni

1. Patterns of host acceptance by Diachasmimorpha tryoni (Ashmead), a paras itoid of tephritid flies, were evaluated in relation to host-substrate comp lex, wasp origin, and wasp experience. 2. Naive female D. tryoni originating both from the Mediterranean fruit fly (medfly) Ceratitis capitata (Wiedemann) and the lantana gall fly Eutreta x anthochaeta Aldrich probed medfly-infested coffee fruit two to six times mo re often than E. xanthochaeta-inhabited lantana galls. No significant diffe rences were detected between the two groups of parasitoids in patterns of p robing response to medfly-infested coffee fruit or to E, xanthochaeta galls . 3. An 18-h pretest exposure to medfly-infested coffee fruit or E. xanthocha eta-inhabited galls affected the probing response of D, tryoni to E. xantho chaeta galls significantly, but did not affect the probing response to medf ly-infested coffee fruit. Diachasmimorpha tryoni exposed to E. xanthochaeta galls probed E. xanthochaeta galls two to three times more often than naiv e wasps, and seven to 11 times more than wasps exposed to medfly-infested c offee fruit. Regardless of the prior exposure treatments, a high proportion (75-100%) of the test parasitoids probed medfly-infested coffee fruit. 4. Parasitoid acceptance of less-preferred hosts or host-substrate complexe s may be more amenable to conditioning through prior experience (i.e. learn ing) than preferred host-substrate complexes. The relevance of these findin gs to host range expansion of parasitoids used in fruit fly biological cont rol is discussed.