ADAPTIVE VARIATION IN HOST-SELECTION BEHAVIOR OF ASOBARA-TABIDA, A PARASITOID OF DROSOPHILA LARVAE

1. The braconid Asobara tabida is a widespread parasitoid of Drosophil a larvae in fermenting substrates. 2. Across its geographic range, sur vival probability in D. subobscura larvae is high and fairly constant; survival probability in D. melanogaster larvae shows much variation. 3. When females of different strains are offered a choice between larv ae of the two host species, the degree of preference for D. subobscura larvae is linked to the difference in survival probability in the two host species. 4. Host selection behaviour of the females matches the predictions made by an optimal foraging model. 5. Survival probability in D. melanogaster also depends on temperature and host selection beh aviour appears to be influenced by temperature as well. 6. It is concl uded that host selection behaviour of A. tabida is a trait with phenot ypic plasticity on top of genetic differences.