Foraging behaviour, host plant and host location in the aphid hyperparasitoid Euneura augarus

Euneura augarus is a specialized ectohyperparasitoid of conifer lachnids, which causes considerable mortality in mummies of conifer lachnid parasitoids. For the search on a large scale, E. augarus females rely mainly on volatile secondary plant compounds of conifers to locate potential host plants. In the medium‐range (i.e., on a given host plant), females detect the presence of hosts either during spiral search flights or during search by walking. Search flights were more effective when mummies were dispersed, while clumped mummies were mainly found by walking. On ant‐attended trees, E. augarus was not able to forage successfully. Choice experiments with Aphidius ervi‐mummies showed that E. augarus is able to develop in species that are not attacked in the field. We hypothesize that the proximate mechanism of host plant specificity, and as a consequence, host aphid specificity seems to be the use of typical conifer volatiles for host finding which provide the ‘search image’ for the species.