Eyespot peek-a-boo: false eyes improve the survival of caterpillars in leaf rolls

Abstract

Deimatic displays typically involve body parts that can conceal or reveal visual signals, potentially reducing detectability at a distance while startling predators up close. Some species may achieve this “conceal-then-reveal” effect using modified aspects of their environment (environmental deimatism hypothesis). The larvae of spicebush swallowtail butterflies (Papilio troilus) possess large eyespots, and rest in leaf rolls during the day. I tested the hypothesis that leaf rolls reduce eyespot conspicuousness while maintaining eyespot effectiveness by comparing avian predation on 659 artificial larvae: eyespotted and non-eyespotted, presented in leaf rolls or on open leaves. Leaf rolls reduced predation regardless of color pattern. Eyespots also reduced predation, but only for artificial larvae in leaf rolls. On open leaves, eyespots neither increased nor decreased predation. These results suggest that eyespots and leaf rolls can combine to create a deimatic display – and that this strategy likely evolved to enhance existing antipredator effects of leaf rolls.