Learning pays off: influence of experience on host finding and parasitism in Lariophagus distinguendus

1. The influence of experience on egg maturation, parasitism rate, and beha viour during host searching was investigated for Lariophagus distinguendus (Forst.) (Hymenoptera: Pteromalidae) parasitizing larvae of the granary wee vil Sitophilus granarius (L.) in grains of wheat Triticum aestivum L. 2. Dissection of female parasitoids and parasitism bioassays at high host d ensity revealed that experience with hosts (e.g. by oviposition or by host feeding) is not required either for triggering oogenesis or for oviposition . 3. In parasitism experiments at low host density, when single host-infested grains were offered within a bulk of healthy grains, host finding and para sitism rate were increased by experience. 4. Behavioural observations revealed that searching time required for findi ng an infested grain was shorter for experienced parasitoids than for naive parasitoids, because travel time from grain to grain is shorter for experi enced parasitoids, and because experienced parasitoids spend less time than naive parasitoids on noninfested grains. 5. In conclusion, experience due to host exposure increases parasitism and thereby the fitness of the parasitoids. It is discussed that this increase is more likely due to learning than to different egg load dynamics of exper ienced parasitoids.