DYNAMIC HOST FEEDING BY THE PARASITOID APHYTIS-MELINUS - THE BALANCE BETWEEN CURRENT AND FUTURE REPRODUCTION

1. In many species of parasitoid Hymenoptera, adult females can use hosts either for oviposition or 'host feeding'. Oviposition is current reproduction and host feeding represents investment towards future reproduction. 2. We investigated the influences of egg load, diet, age, experience and host size on host-feeding behaviour in the aphelinid parasitoid Aphytis melinus attacking oleander scale Aspidiotus nerii (Homoptera: Diaspididae). Hosts were either rejected, used exclusively for host feeding, used for both oviposition and host feeding concurrently, or used exclusively for oviposition. When hosts were used for both oviposition and host feeding, parasitoid progeny did not develop to adulthood. 3. Behavioural records were analysed with the logistic regression model, a statistical tool for assessing the relative contributions of multiple, potentially correlated, variables. 4. Variation in egg load was obtained by (i) using diet and age treatments to manipulate the rate of egg resorption by parasitoids and (ii) taking advantage of size-related differences in egg load. Parasitoids with lower egg loads were more likely to host feed than to ovipost. This result is consistent with recently developed theory. 5. During their first-ever encounter with a host, parasitoids that had been fed a pure sucrose diet during their adult life were more likely to host feed than were parasitoids fed a sucrose diet supplemented with yeast. 6. Contrary to theoretical predictions, younger parasitoids were not more likely to host feed than older parasitoids. 7. Smaller hosts were (i) more frequently used for host feeding than were larger hosts, and (ii) less suitable for progeny development than were larger hosts.