Visual discrimination of predaceous ants by egg-laying butterflies

Host plant selection in insect herbivores is carried out by the egg-laying female, and offspring survival frequently differs among plants due to variation in the presence of natural enemies. Thus information about predation risks is critical for gravid females, and natural selection should favor the ability to detect enemies and to select enemy-free foliage. This capability was demonstrated for a nymphalid butterfly (Eunica bechina) whose caterpillars feed on an ant-defended plant (Caryocar brasiliense) in the Brazilian savanna. Experiments with dried ant specimens pinned to leaves revealed that butterflies utilize ant size and form as visual recognition cues to avoid ovipositing on plant locations occupied by aggressive ants more likely to kill larval offspring. This shows that visual identification of predators mediates egg-laying decisions by Eunica, which can also discriminate among different species of potential predators. This unusual ability permits herbivore specialization on an ant-defended food plant (supported by FAPESP, CAPES, CNPq, NSF)