Influence d'une alimentation préalable et du jeûne sur l'apparition de la recherche intensive des proies chez Semiadalia undecimnotata

Résumé Les prédateurs qui vivent aux dépens de ressources alimentaires groupées, modifient leur mode de déplacement après la capture et l'ingestion d'une proie. Ils passent de la recherche extensive (déplacements rapides et linéaires) à la recherche intensive (déplacements lents et sinueux). Chez les adultes et les larves de dernier stade de la coccinelle Semiadalia undecimnotata Schn. (Col., Coccinellidae ), dans les premières heures qui suivent leur naissance ou leur mue, l'ingestion d'un premier puceron ne modifie pas les caractéristiques locomotrices individuelles: les déplacements restent de type extensif. Au début de chaque stade, cette coccinelle présente une période de sensibilisation à la proie rencontrée. Durant ces laps de temps, elle doit consommer plusieurs proies avant d'ětre capable d'adopter la recherche intensive. L'existence d'une période de jeûne avant cette première prise alimentaire favorise, au contraire, l'adoption de la recherche intensive. Abstract Effect of a prior feeding period and of fasting on the appearance of intensive search of preys with S. undecimnotata The ladybird, Semiadalia undecimnotata , like all other entomophagous insects feeding on relatively sedentary prey, exhibits two types of walking pattern during the search for prey: extensive and intensive search. The latter is engaged following detection of visual or chemical cues. Changes in the ladybird search pattern: extensive search ‐ a single prey capture ‐ intensive search, were investigated in relation to experience of prior feeding‐periods (experienced coccinellids) or to lack of such experience (naïve coccinellids) and with respect to changes in duration of fasting. The analysis of their pathways was performed initially by comparison of three locomotory paramètres: the number of stops (number/s), the walking speed (mm/s) and the turning‐rate (degrees/s), and subsequently by statistical classification (principle components analysis). Unlike experienced coccinellids, observations of naïve coccinellids, indicate that a single feeding session during the three to five hours after emergence of an adult, or ecdysis of the larva, will change the walking pattern slightly. These animals will maintain extensive search or adopt a particular, intermediate locomotory pattern which is a development of extensive search but do not adopt intensive search. Fasting, for periods over twelve hours, favoured intensive search in populations studied. It is probable that the requirement to feed on more than one prey item before adopting intensive search involves concepts such as forms of learning (sensitization).