Summary. An oviposition-deterring pheromone (ODP) of the European cherry fruit fly Rhagoletis cerasi L. was isolated from faeces using cellulose and several reverse phase TLC and HPLC procedures. The biological activity was evaluated by means of behavior tests and by electrophysiological recordings from tarsal contact chemoreceptors. The compound was structurally characterized as a N[15(fl-glucopyranosyl)oxy-8-hydroxypalmitoyl]-taurine by spectroscopic means. The configurations of C-8 and C-15 of the fatty acid constituent remain to be established by synthetic work.

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.

Electroantennogram (EAG) recordings from the antennae of a highly specialized phytophagous species — the oak flea weevil, Rhynchaenus quercus L. — revealed two general properties of its antennal olfactory system: (1) a high and to some extent selective sensitivity to chemotaxonomically nonspecific compounds, namely the so‐called “general green leaf volatiles” as well as to geraniol and linalool, (2) a lack of marked differences in the general excitation level caused by stimulation with vapours from leaves of both host plants and non‐host plants. It was also observed, that the shapes of EAG's evoked by vapours from cut leaves and general green leaf volatiles differed from those elicited by corresponding concentrations of geraniol and linalool, where recovery was distinctly slower. The results of EAG tests suggest that the general green leaf volatile complex is important in host‐odour perception by the oak flea weevil. A possible function of these compounds in host‐plant odour discrimination is discussed. ZUSAMMENFASSUNG Wirtspflanzenabhängige Eigenschaften des Geruchsystems der Fühler des Eichenblattflohs, Rhynchaenus quercus. Elektroantennographische Studie Elektroantennographische Aufzeichnungen an Fühlern einer hochspezialisierten phytophagen Art, des Eichenblattflohs Rhynchaenus quercus L. zeigten zwei allgemeine Eigenschaften des Geruchsystems der Antennen: Erstens ist eine hohe und teilweise selektive Empfindlichkeit auf chemotaxonomisch nicht spezifische Verbindungen, besonders auf die “allgemeinen Blattgründämpfe” wie auch auf Geraniol und Linalool vorhanden. Zweitens fehlen ausgeprägte Unterschiede im allgemeinen Erregungsniveau hervorgerufen durch flüchtige Stoffe von Wirtspflanzen einerseits und Nichtwirtspflanzen andererseits. Es wurde auch beobachtet, dass die Form der EAGs hervorgerufen durch zerschnittene Blätter oder „allgemeine Blattgründämpfe” verschieden war von denjenigen verursacht durch Geraniol und Linalool, wo die Erholung eindeutig langsamer war. Die Resultate der EAG deuten darauf hin, dass der Komplex der “allgemeinen Blattgründämpfe” wichtig ist bei der Wahrnehmung der Wirtspflanzengerüche durch Rhynchaenus quercus. Eine mögliche Funktion dieser Verbindungen bei der Erkennung der Wirtspflanzen wird diskutiert.

Electrophysiological recordings from the tarsal D-sensilla of mature, 5-7-day-old female European cherry fruit fly (Rhagoletis cerasi L.) revealed that a large proportion of sensilla showed no sensory activity in response to stimulation with the oviposition deterring pheromone ('ODP') or sucrose. In contrast, good recordings were obtained from almost all sensilla in freshly emerged, 1-day-old flies. Ageing, nutritional state and contamination were excluded as possible major factors influencing the responsiveness of the D-sensilla. The study of the variability in responsiveness of the sensilla of 1-day-old flies among different tarsomers, among tarsi of the same individual and among individuals, revealed that the major source of variability was among individuals.Individual flies were also affected by the humidity in the holding cages: relative air humidity of less then 75% for 4-6 days was shown to reduce the number of D-sensilla giving recordings with a good signal-to-noise ratio. The D-sensilla on the most distal tarsomers were affected most by the reduced ( 3 6 5 5 % r.h.) air humidity. Flies which had contact with plant leaves showed less reduction in responsiveness at low air humidity (40% r.h.) then flies without leaf contact.

The mating behaviour of two sycamore inhabiting aphids, Periphillus acericola and Drepanosiphum platanoidis, was observed. A description of the mating behaviour of male P. acericola is given. This behaviour comprised «searching movement», «antennal contact», «excitation» (presumably related to pheromone perception), «copulation attempt», «genital contact», «dismounting» and «moving away». Mating in both species took place on senescent leaves where wingless, sexual females matured. Such females formed lose aggregations on the leaves. Mating occurred before they left the leaves to oviposition in crevices in the bark. Males remained on particular leaves where they increased their fitness by maximizing the number of copulations with such females. This kind of competition could evolve from a strongly female biased sex ratio, accessibility of the females, female opportunistic choice of mates and the possible lack of sperm precedence.