Foraging behaviour and sequential multisensory orientation in the aphid parasitoid, Pauesia picta (Hym., Aphidiidae) at different spatial scales

Foraging females of Pauesia picta, a parasitoid of the conifer aphid Cinara pinea on pine, used a variety of host plant or host-borne cues to find and recognize its aphid hosts. For long-range detection, females rely mainly on secondary plant compounds to locate potential host plants. In the medium-range (i.e. on a given host plant), females detected the presence of hosts by encounters with honeydew-collecting workers of the ant Formica polyctena and by perceiving host-borne cues. For short-range detection, after the discovery of an aphid colony, P. picta females recognize hosts visually. Subsequent antennal tapping, a tactile stimulus, prevents dispersal of aphids and increases the oviposition success of the parasitoid. The final host acceptance is obviously triggered by signals located in the epicuticle of the host. The results demonstrate the importance of sequential multisensory foraging that correspond to a diminishing distance between the parasitoid and the host.