Do Hind Wing Eyespots of Caligo Butterflies Function in Both Mating Behavior and Antipredator Defense? (Lepidoptera, Nymphalidae)

In general, butterfly ventral hind wing eyespots are considered to play a role in predator–prey interactions. These eyespots are prominent wing pattern elements in Brassolini butterflies, and they vary in size, position, and number across taxa. Female Caligo Hubner, 1819 (Lepidoptera, Nymphalidae) appear to use the large eyespots of lekking males as a mate-locating cue, but female Opsiphanes Doubleday, 1849 (Lepidoptera, Nymphalidae) do not because males patrol to find mates. These behaviors led us to predict that male Caligo should have larger eyespots than females, but eyespot size would not differ between sexes in Opsiphanes. Our analyses supported these predictions. As displacement of the eyespots to the center of the wing might make them more conspicuous, we asked if eyespot position and size covaried across the Brassolini phylogeny. While we found a positive association between position and size, the relationship of these two variables contained significant phylogenetic signal. Two Brassolini species show strong sexual dimorphism where females converge on the color pattern of sympatric species of Caligo. Their ventral hind wing eyespots are much larger than those of close relatives, approximating those of Caligo, and further reinforcing the importance of ventral hind wing eyespots as a visual signal in this group of butterflies. Importantly, our results suggest that, in addition to antipredation defense, ventral hind wing eyespots can function in mating activities, and consequently they might be evolving under both natural and sexual selection in Caligo butterflies.