Collective foraging patterns of field colonies ofMalacosoma disstriacaterpillars

Abstract

AbstractWe monitored 12 colonies of the nomadic social caterpillarMalacosoma disstriaHübner (Lepidoptera: Lasiocampidae) on trembling aspen,Populus tremuloidesMichx. (Salicaceae), under field conditions in spring 2007. We examined cohesion and synchronization of colonies and spatiotemporal activity patterns to compare foraging in the field with the results of laboratory studies and with foraging by central-place foragers. All colonies were highly cohesive; fragmentation was observed only three times. Activity was highly synchronous within colonies, with clear alternation between periods of activity and quiescence. Colonies performed 4.25 ± 0.12 (mean ± SE) activity bouts per day, and foraging was more likely to occur in the early morning than at midday. Colony activity was weakly correlated with temperature. In contrast to that ofM. americanum(F.), the foraging schedule was flexible: foraging was observed at all recorded times and temperatures. Colonies searched for a new feeding site every 2.54 ± 0.37 days (mean ± SE) after a food source was depleted. Time spent at a food source decreased with colony size, and distance travelled between food sources increased with instar.Malacosoma disstriacaterpillars on trembling aspen are not very selective; rather, they minimize movement, thus decreasing potential contacts with predators.