10183hunter Abstract Group living has both costs and benefits for plant-feeding insects, but defense against predators is the most widely acknowledged benefit. Gregarious folivores typically have warning coloration and elaborate anti-predator defenses. To see if protection from predators generally results from gregariousness, I compared the shapes of published survivorship curves of externally feeding, gregarious and solitary Lepidoptera and Symphyta.
Gregarious species are less likely than solitary species to die in the larval stages.
However, solitary species that have anti-predator defenses do not have higher larval survival compared to gregarious species. This result, along with evidence from experimental manipulations of group size, suggests that repellent defenses per se do not increase survival of gregarious larvae. Group behaviour is undoubtedly important in affecting the higher larval survival of gregarious species, but we currently cannot determine whether predator learning, dilution of risk, or rapid development contribute most to increasing survival.