Effect of low temperature exposure on oviposition behaviour and patch exploitation strategy in parasitic wasps

Learning of olfactory and gustatory cues occurs throughout the adult stage of parasitoids, particularly during host location and patch exploitation. A loss of learning capacities could affect both the whole host-parasitoid system and the wasps' reproductive success. We analysed the effect of low-temperature exposure on learning, patch exploitation strategies and patch-leaving rules used by Anaphes victus (Hymenoptera: Mymaridae). Females were stored 0, 3, 6 and 12 weeks at 4°C at the second larval instar. After emergence, females were offered three successive patches containing 16 hosts, of which 0, 50 and 100%, respectively, were parasitized, and their foraging behaviours were recorded. Cold-exposed females oviposited fewer eggs, seemed less able to learn external marks (or did not use their learning capacities), oviposited more in already parasitized hosts and used different patch-leaving rules to control females. The degree of the change in behaviour was positively correlated with the duration of cold exposure. Low-temperature exposure thus affected the reproductive success, expression of learning, host discrimination ability and patch-leaving decision rules of the parasitic wasps. We discuss the implications of these effects on the pattern of patch exploitation for biological control and field situations.