none Pieris rapae; HYMENOPTERAN-PARASITES; Cotesia rubecula; Parasite inflight orientation to plant/host complex odours; Olfactory experience effects on sensitivity Cotesia rubecula; CHEMORECEPTION-; Plant/lepidopteran host complex odours; EXPERIENCE-; Olfactory experience effects on sensitivity to plant/host complex odours; ORIENTATION-; Inflight orientation to plant/lepidopteran host complex odours; LEPIDOPTERAN-HOSTS; Pieris rapae; Plant/host complex odours, inflight orientation relations; Olfactory experience effects on sensitivity Plasticity in in-flight orientation to odours from the plant-host complex (PHC: plant infested by the host) was investigated in Cotesia rubecula , a specialist larval parasitoid of Pieris rapae , which feeds almost exclusively upon cruciferous plants. A wind tunnel was used to study effects of both concentration of volatile emissions and females' experience. A low proportion of naive wasps located weak odourant sources, i.e. either a single cabbage leaf or a leaf with two first stadium P. rapae larvae. This rate could be elevated by increasing the odour concentration or by providing the wasps with either a previous oviposition experience on the PHC or an exposure to the PHC odour. Previous oviposition on washed larvae (diet-fed, starved and then rinsed with distilled water) in an odourless environment had no effect, which suggested that increased sensitivity to the PHC odour resulted from olfactory experience.