Shiny wing scales cause spec(tac)ular camouflage of the angled sunbeam butterfly, Curetis acuta

Abstract

The angled sunbeam butterfly, Curetis acuta (Lycaenidae), is a distinctly sexually dimorphic lycaenid butterfly from Asia. The dorsal wings of female and male butterflies have a similar pattern, with a large white area in the female and an orange area in the male, framed within brown–black margins. The ventral wings of both sexes are silvery white, which is caused by stacks of overlapping, non-pigmented, and specular-reflecting scales. With oblique illumination, the reflected light of the ventral wings is strongly polarized. We show that the silvery reflection facilitates camouflage in a shaded, foliaceous environment. The ecological function of the silvery reflection is presumably two-fold: for intraspecific signalling in flight, and for reducing predation risk at rest and during hibernation. Biological Journal of the Linnean Society, 2013, 109, 279–289.

camouflage, iridescence, Lycaenidae, polarization, scattering