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

Summary 1. Patterns of host acceptance by Diachasmimorpha tryoni (Ashmead), a parasitoid of tephritid flies, were evaluated in relation to host–substrate complex, 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 xanthochaeta Aldrich probed medfly‐infested coffee fruit two to six times more often than E. xanthochaeta ‐inhabited lantana galls. No significant differences were detected between the two groups of parasitoids in patterns of probing response to medfly‐infested coffee fruit or to E. xanthochaeta galls. 3. An 18‐h pretest exposure to medfly‐infested coffee fruit or E. xanthochaeta ‐inhabited galls affected the probing response of D. tryoni to E. xanthochaeta galls significantly, but did not affect the probing response to medfly‐infested coffee fruit. Diachasmimorpha tryoni exposed to E. xanthochaeta galls probed E. xanthochaeta galls two to three times more often than naive wasps, and seven to 11 times more than wasps exposed to medfly‐infested coffee 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 complexes may be more amenable to conditioning through prior experience (i.e. learning) than preferred host–substrate complexes. The relevance of these findings to host range expansion of parasitoids used in fruit fly biological control is discussed.