Social cues and following behavior in the forest tent caterpillar

Colonies of the social caterpillar Malacosoma disstria Hubner (Lepidoptera: Lasiocampidae) travel in groups following silk trails marked with pheromone. This study examined first, the cues involved in following behavior and second, the responses to these cues at different larval stadia. Both second and fourth instar larvae discriminated between fresh and older trails, and travelled faster in the presence of trails. In addition to trail following, young caterpillars exhibited leader following, which might be particularly important in exploring unmarked territory. Indeed, second instar caterpillars were more likely to travel together when trails were absent. Fourth instar larvae exhibited greater independent locomotion in the absence of trails than did younger larvae. These findings help explain patterns of social behavior observed in forest tent caterpillar colonies in the field.