Odour conditioning of ovipositor probing in a parasitic wasp

We investigated the occurrence of odour learning in the ovipositor probing activity of Leptopilina boulardi, a parasitoid of Drosophila larvae. A device was set up to observe the probing behaviour in response to an odour. Systematic and persistent probing in response to the odour (banana) was observed after associative conditioning, i.e., after the odour had been experienced while ovipositing. The percentage of females responding to the odour was also increased after oviposition experience alone or preceded by odour exposure. The induced responses were then less persistent than after associative conditioning, and also less selective because probing was triggered as a consequence of oviposition experience and not only upon odour delivery. This is the first demonstration of the role and nature of odour learning in ovipositor probing behaviour, the final step of host location by Leptopilina sp., and this activity appears to be much modulated by the wasps experience.