none Aphidius ervi; CHEMORECEPTION-; FORAGING-; FLIGHT-; Behaviour, attraction to plants with hemipteran host; HEMIPTERAN-HOSTS; Acythosiphon pisum; Chemosensory attraction to infected plants Acyrthosiphon pisum; HYMENOPTERAN-PARASITES; Aphidius ervi; Parasite attraction to host plants The flight behaviour of the aphid parasitoid Aphidius ervi Haliday (Hymenoptera: Braconidae) has been studied in a wind tunnel, in response to the following natural odour sources: broad bean plants infested with Acyrthosiphon pisum (Harris) (Homoptera: Aphididae) (PHC, plant-host complex), damaged broad bean plants from which the aphids were removed (HDP, host damaged plants), aphids (H, host) and uninfested broad bean plants (P, plant). The most attractive odour sources were PHC and HDP, which both stimulated a similar high number of oriented straight flights. In contrast, H and P were much less attractive and did not seem to be important in the long range attraction of the parasitoids.