INFLUENCE OF 2 SUCCESSIVE LEARNING-PROCESSES ON THE RESPONSE OF EUPELMUS-VUILLETI CRW (HYMENOPTERA, EUPELMIDAE) TO VOLATILE STIMULI FROM HOSTS AND HOST PLANTS

Eupelmus vuilleti (Crw) is a solitary ectoparasitoid of several bruchi d species which develop inside Leguminosae seeds. In this hymenopteran a preemergence learning process is responsible for a specific respons e of females toward the host and host-plant volatiles. This learning o ccurs after the imaginal malt, while the adult remains in the larval c hamber of its host. The persistence of the response toward host and ho st-plant volatiles of females reared on Bruchidius atrolineatus (Pie) larvae developing in Vigna unguiculata (Walp) seed was investigated in this study. In the absence of any reinforcement, the response toward B. atrolineatus larvae persisted for 6 days after female emergence fro m the seeds, whereas the response toward V. unguiculata seed volatiles was maintained for 7 days. Our experiments showed that a later learni ng process also takes place in E. vuilleti. An ovipositional experienc e on a given plant-host complex enabled females to learn the stimuli f rom that complex. This learning occurred even if the complex experienc ed during oviposition differed from the one on which females were rear ed. After an ovipositional experience an a new plant-host complex, the response acquired through preemergence learning was maintained, These experiments demonstrate that the E. vuilleti females can memorize cue s from several species during successive learning processes. The adapt ive significance of these learning capacities, which confer an importa nt behavioral plasticity to this generalist parasitoid, is discussed.