SPRING BEHAVIOR OF THE PLUM CURCULIO (COLEOPTERA, CURCULIONIDAE) WITHIN CAGED DWARF APPLE-TREES

Spring behavior of adult plum curculios, Conotrachelus nenuphar (Herbs t), was observed for 2 yr within field cages containing dwarf apple tr ees. Variations in total activity were highly (r2 = 0.912) related to air saturation deficit. Differences in crawling, feeding, mating, and egg-laying behaviors were significantly related to phenological stages , but not to meteorological conditions. All frequent behaviors, except resting, were more frequent between 1800 and 0000 hours, or were equa lly frequent with respect to hour classes. Behaviors varied with tree height and substrates occupied. Total activity was greater in trees (3 2% of observations of adults) than on the ground (11% of observations) , but crawling was equally frequent in both locations (16% of observat ions). Resting occurred mostly on the ground, and feeding mostly on fr uits, but feeding also occurred occasionally on flowers and on recentl y grown shoots. Mating took place from ''full bloom'' to ''fruit set'' stages, and occurred mostly on twigs, in the upper half of trees. Fal ling from trees was often followed by crawling on the ground to adjace nt trees, which were subsequently invaded. Plum curculios flying from tree to tree were seen landing on various host structures and on the w alls of the cage. Thus, dropping, crawling, and flying are important m eans of dispersal.