Tailor-made learning and memory in parasitoids

Vet, L.E.M.; Smid, H.M.


Studies on learning in insect parasitoids have commonly addressed the effect of experience on the response to specific stimuli, and have yielded hypotheses on the adaptive value of such learning in foraging parasitoids. Only recently have researchers begun to use parasitoids to study the mechanistic aspects of learning. Differences in the expression of learning between closely related species create excellent opportunities to study species-typical learning. Our model system consists of two co-existing Cotesia parasitoid species that occupy slightly different niches. In the Netherlands, Cotesia glomerata mainly attacks the gregariously feeding caterpillars of the large cabbage white Pieris brassicae while Cotesia rubecula is specialized on the solitarily feeding small cabbage white Pieris rapae. Both parasitoid species are capable of learning to prefer the odours of plants on which they found their host caterpillars. However, they clearly differ in the functional requirements for the formation of long-term memory (LTM) of these plant odours. We argue that this reflects a difference in the wasp’s searching behaviour in nature, related to the distribution of their caterpillar hosts. We expect such tailor-made learning and memory to be more common in parasitic wasps than presently assumed. Species 1: Hymenoptera Braconidae Cotesia glomerata Species 2: Hymenoptera Braconidae Cotesia rubecula Species 3: Lepidoptera Pieridae Pieris rapae (cabbage white butterfly)