Colors and pterin pigmentation of pierid butterfly wings.

The reflectance of pierid butterfly wings is principally determined by the incoherent scattering of incident light and the absorption by pterin pigments in the scale structures. Coherent scattering causing iridescence is frequently encountered in the dorsal wings or wing tips of male pierids. We investigated the effect of the pterins on wing reflectance by local extraction of the pigments with aqueous ammonia and simultaneous spectrophotometric measurements. The ultraviolet-absorbing leucopterin was extracted prominently from the white Pieris species, and the violet-absorbing xanthopterin and blue-absorbing erythropterin were mainly derived from the yellow- and orange-colored Coliadinae, but they were also extracted from the dorsal wing tips of many male Pierinae. Absorption spectra deduced from wing reflectance spectra distinctly diverge from the absorption spectra of the extracted pigments, which indicate that when embedded in wing scales the pterins differ from those in solution. The evolution of pierid wing coloration is discussed.