LEARNING AFFECTS HOST DISCRIMINATION BEHAVIOR IN A PARASITOID WASP

Learning is generally predicted not to be important in host discrimina tion by parasitoids, because the stimuli involved are less variable th an those used in habitat location. However, Anaphes victus (Hymenopter a: Mymaridae), an egg parasitoid of Listronotus oregonensis (Coleopter a: Curculionidae) apparently learns to associate external pheromones w ith the presence of a conspecific in a host. In this species, females can reject a parasitized host either after antennal drumming (antennal rejection) or after the insertion of their ovipositor (sting rejectio n). When they encountered a series of parasitized hosts, females A. vi ctus learned to associate the presence of the external pheromone with the presence of the internal one. Learning lasted less than 4 h and oc curred earlier in a series when the female marking the egg and the one detecting that mark were close relatives. This behavior could be adap tive because antennal rejection is faster than sting rejection.