Although several species of the genus Cotesia are used in biological control programs against insect caterpillars throughout the world, little is known of their oviposition behavior. We describe here the types and distribution of antennal sensilla in Cotesia plutellae, a larval parasitoid of Plutella xylostella, and we analyze its oviposition behavior. Seven types of sensilla were found on both males and females. Only sensilla trichodea type II, with a putative contact chemoreceptive function, was significantly more abundant in females than in males, and its morphology and position on antennomeres were linked to the antennation behavior used by females during host search. We conclude that gustatory stimulus following antennal contact is probably the key stimulus inducing oviposition behavior. The sensilla type assumed to be implied in oviposition behavior was present in C. plutellae but not in two closely related species (C. glomerata and C. rubecula), which is discussed.
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