Associative odour learning affects mating behaviour in Aphidius ervi males (Hymenoptera: Braconidae)

We used the aphid parasitoid Aphidius ervi reared in its host Acyrthosiphon pisum to examine if male sexual attractive responses can be conditioned to an odour (vanilla) that is not present in the natural environment. We used prior mating experience (exposure to females) as a non-conditioning stimulus and vanilla odour as a conditioning stimulus. The behavioural responses were tested in a glass Y-olfactometer just after eclosion (i.e., initial response) and after a training experience (i.e., trained response). During the 10-min training period individual males were allowed to copulate with a virgin female with or without vanilla odour present, or were exposed only to vanilla odour. Wing fanning was a recurrent behaviour which denoted increased sexual attraction to a volatile stimulus. Total time and time doing wing fanning in each olfactometer arm were determined. Vanilla odour, which initially did not elicit sexual-related behaviours, triggered strong sexual attractive responses when males were trained to females plus vanilla odour. Neither copulation only nor vanilla odour only treatments elicited such behaviours in trained males. The results are discussed in terms of parasitoid learning ability and its ecological consequences.