LEADERSHIP-BEHAVIOR IN SAWFLY LARVAE PERGA-DORSALIS (HYMENOPTERA, PERGIDAE)

Australian sawflies in the genus Perga have gregarious larvae which di sperse to feed upon Eucalyptus foliage at night. To investigate possib le polyethism in the larvae of P. dorsalis, we labelled individuals wi th oil paints and recorded their positions on consecutive nights. A su bgroup of about 20% of the larvae preferentially occupied the outer po sitions in the resting colony and appeared to lead the foraging expedi tions. Marking itself did not induce this leadership behaviour, and le aders were quick to regain outer positions if removed and placed in th e centre of the colony. In the context of polyethism in pergid larvae, we discuss the non-viability of small colonies, differential attack r ates by parasitoids and predators, petiole-chewing behaviour by leader s, and possible differences in the dispersal behaviour of larvae (in t ime) and adults (in space).