ABSTRACT

We review key ecological and behavioral mechanisms underlying the origin and maintenance of larval sociality in the Lepidoptera. Using communication contexts of group defense, cohesion and recruitment as a framework, we relate social complexity among gregarious caterpillars to three patterns of foraging: patch–restricted, nomadic, and central–place. A review of the incidence of larval gregariousness in the Lepidoptera demonstrates that sociality is widespread in the order, occurring in twenty or more families representing thirteen ditrysian superfamilies, and it is likely to have evolved numerous times in response to different selective pressures. We specifically address the role of sociality in larval defense and resource use, with a focus on (1) signal enhancement in communication systems, (2) differential larval vulnerability, and (3) ant association. Larval Lepidoptera experience the greatest likelihood of mortality in the earliest instars; larval sociality enhances defensive and resource–exploitation signals in these instars, positively influencing survivorship and larval growth. Disease, predation and parasitism, nutrition, and inclusive fitness are discussed in terms of costs and benefits of group living. Finally, we identify two areas where additional research will contribute significantly to an understanding of social evolution in the Lepidoptera: (1) comparative phylogenetic studies, using ecological and communicative characters to trace the origins of caterpillar societies and transitions among them, and (2) larval behavior and ecology, focusing on kin discrimination abilities, assessment of colony genetic structure, and most importantly on the means and contexts of caterpillar communication.