The role of plant chemical cues in determining host preference in the generalist aphid parasitoid Aphidius colemani

The host preference behaviour of the generalist aphid parasitoid Aphidius colemani was investigated using a Y-tube olfactometer. Female A. colemani showed a preference for the host-plant complex on which they had been reared, even though the same aphid host was involved, demonstrating a host plant preference. This preference was not evident when the parasitoids were dissected from their mummies prior to adult emergence. Host plant preference exhibited during host selection appeared to be induced by chemical cues encountered on the mummy case at the time of emergence, but preferences could be changed by subsequent foraging experiences. It is concluded that plant chemical cues play a major role in determining initial preferences through a process of emergence conditioning but that learning processes, involving cues encountered during oviposition in or contact with the host, can modify these initial preferences.