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Olfactory responses of parasitoids can be variable. This was shown by olfactometer experiments with females of two sibling Asobara species, larval endoparasitoids of Drosophilidae. Oviposition experiences of adult female parasitoids significantly altered their behavioural responses in microhabitat and host location. Females needed prior exposure to a host before they were capable of using volatile compounds related to the presence of their host. Asobara tabida (Nees) attacks Drosophila in fermenting fruits and A. rufescens (Foerster) attacks Drosophilidae in decaying plant materials. Naïve females show a strong preference for the odour of their own microhabitat. After experience with their own host and microhabitat, females were repelled by odours of the other microhabitat. lsquoEnforcedrsquo experience with this repellent microhabitat in the laboratory modified the olfactory response from repellency to attraction. It was shown that even the microhabitat odour preference pattern could be changed through experience. This kind of behavioural flexibility may be the rule rather than the exception in many other Hymenopterous parasitoids.