Behavioural events underlying observations of uniform egg dispersion in field populations of the cabbage seed weevil, Ceutorhynchus assimilis, among winter rape, Brassica napus, seed pods (siliques) were investigated. We observed that each act of egg deposition into a pod was followed by specific and fixed behaviour in which females brushed the pod surface with a brush‐like structure on the ovipositor. Evidence is provided that chemical marking of the pod surface occurs during brushing, resulting in deterrence of repeated oviposition into the same pod. Ecological implications of pod marking by cabbage seed weevils as well as similarities with the corresponding behaviour of various host marking insects are discussed. RÉSUMÉ Comportement de ponte et marquage des siliques par Ceutorhynchus assimilis L'examen a porté sur les traits comportementaux responsables de l'observation dans la nature d'une distribution uniforme des œufs de Ceutorhynchus assimilis dans les siliques de Brassica napus. Nous avons observé qu'après chaque acte de dépôt d'œufs dans une silique succède un comportement spécifique et fixé pendant lequel la femelle brosse la surface de la silique avec une structure en brosse de l'ovipositeur. Nous avons pu démontrer que pendant ce brossage, la surface de la silique est marquée chimiquement, ce qui dissuade toute ponte répétée dans la même silique. La discussion porte sur les conséquences écologiques du marquage des siliques par C. assimilis et sur les analogies avec les différents comportements de marquage d'hôtes chez les insectes.

The study was conducted to determine how various factors, including learning, influence the host-selection behavior of the larval parasitoid Cotesia (=Apanteles)marginiventris (Cresson). Frass, silk, and feeding damage fromSpodoptera frugiperda (J.E. Smith) larvae elicited visits and antennal examinations by females of the parasitoid. Learning played a role in the effective response to these stimuli in that previous contact experience with hosts and/or chewed leaves, exuviae, frass, or hemolymph significantly enhanced the response of the parasitoid. Previous contact with host plants alone did not improve the responses. Experienced parasitoids were more active and spent less time at rest than inexperienced parasitoids. Previous experience was also found to be of significant importance in the ability of the parasitoid to discriminate between parasitized and unparasitized host larvae.

No abstract