Individual consistency, learning and memory in a parasitoid fly, Ormia ochracea

Search images are expected to be important components of predator and parasitoid search strategies as they reduce the search time for prey and hosts. Fixed search images, however, may constrain predators and parasitoids, and render them ineffective at switching to new more abundant prey or hosts. For switching behaviour to be effective, parasitoids need to be able to learn cues associated with abundant hosts, and they need to be able to extinguish preferences for the cues of hosts that are no longer abundant. Here we use the Gryllus cricket and Ormia ochracea parasitoid fly system to show (1) individual consistency in fly preference for song in the field, (2) learning of host song in the laboratory and (3) that the flies’ memory for learned host cues is very short term. These results are interesting and novel in several respects. First, our demonstration that O. ochracea satisfies each of the characteristics of an optimally foraging temporary specialist is new. Second, this is only the third demonstration of learning in the Tachinidae, a family of more than 9000 species, all of which are parasitoids. Third, the flexibility inherent in learning and host switching may have been instrumental in allowing expansion of the fly’s geographical and host range.

► We examined host-switching behaviour in the Gryllus cricket–Ormia ochracea parasitoid fly system.
► Flies showed individual consistency in their preference for host song in the field.
► Flies learned host song in the laboratory.
► Flies’ memory for learned host cues was very short term.
► Learning as shown by O. ochracea is rare in the Tachinidae (3 of 9000 species).