Group Foraging and Trail Following Behavior of theRed-headed Pine Sawfly Neodiprion lecontei (Fitch) (Hymenoptera: Symphyta: Diprionidae)

Larval sawfly foraging behavior is understudied in comparison to defoliating Lepidoptera, yet the parallel lifestyles of these groups suggest that similar behavioral and physiological adaptations may have arisen in response to common selective pressures. The red-headed pine sawfly, Neodiprion lecontei (Fitch), is a gregarious diprionid that forages nomadically on a variety of pine species. We investigated the behavioral basis of group foraging in N. lecontei, in particular trail following and colony foraging dynamics, in order to better understand the mechanisms contributing to group cohesion in this species. We show that N. lecontei is, like many social Lepidoptera, a trail follower, showing a strong preference for substrate contacted by foraging conspecifics. This may be the first study to demonstate trail following behavior in a social sawfly. In ad libitum group movement studies, larval groups did not colonize new patches in a single migratory pulse but migrated over a period of hours solitarily or in small groups. Foraging groups remained largely cohesive yet frequently fissioned small groups that dynamically recoalesced during larval development. We speculate that N. lecontei larvae remain cohesive by cueing on a marker derived from their pine host and deposited passively by migrating conspecifics.