Effectiveness of caterpillar defenses against three species of invertebrate predators

The efficacies of larval defenses against invertebrate predators representing different (but overlapping) foraging guilds were compared by offering 34 species (287 individuals) of lepidopteran larvae to Paraponera clavata ants, Apiomerus pictipes bugs, and Polistes instabilis wasps. Overall, the ants were the most likely to eat caterpillar prey, and the wasps were the most cautious. Larval chemistry and diet breadth were significant predictors of rejection by the group of predators; chemically defended specialist herbivores were better protected than generalist herbivores without known chemical defenses. These results provide evidence for the potential importance of predators in maintaining diet breadth of phytophagous insects, and they suggest that plant chemistry is part of a mechanism for restricting diet breadth. Other important larval defenses included size, morphology, and coloration. Large prey (heavier than 1 g) were less acceptable than smaller prey (lighter than 200 mg) for the wasps and bugs but not for the ants; hairs deterred predation by the ants and bugs but not by the wasps; and brightly colored caterpillars were frequently rejected by the wasps but not by the ants and bugs.