Varying and unchanging whiteness on the wings of dusk-active and shade-inhabiting Carystoides escalantei butterflies

Significance Whiteness, although frequently apparent on the wings, legs, antennae, or bodies of many species of moths and butterflies, has often escaped our attention. Here, we investigate the nanostructure and microstructure of white spots on the wings of Carystoides escalantei , a dusk-active and shade-inhabiting Costa Rican rain forest butterfly (Hesperiidae). We identify two types of whiteness: angle dependent and angle independent. We speculate that the biological functions and evolution of Carystoides spot patterns, scale structures, and their varying whiteness are adaptations to the butterfly’s low light habitat and to airflow experienced on the wing base vs. wing tip during flight. Sex and species differences in the location of angle-dependent white spots on the wings may function in both intraspecific and interspecific communication.