Abstract

Studies of butterfly mating behavior have shown that colored wing patterns provide important signals for detection and recognition of a proper mate. Butterfly retinas contain three or four spectral types of photoreceptor, but the spectral locations of peak sensitivity for the types differ greatly among the species. Relative abundance also varies greatly. The goal of this study is to relate the spectral properties of receptor systems to those of wing patterns. Spectral sensitivity functions of each spectral type of receptor are measured optophysiologically. Reflectance spectra of wing patches are measured microspectrophotometrically. Comparing color-image data with receptor data indicates which wing features provide the strongest signals. For example, butterflies of the famous Monarch/Viceroy mimicry complex look very similar to us but not to each other. Monarchs have receptors peaking at ~360, 450, and 550 nm. Viceroys, on the other hand, do not possess the 550-nm type but have instead a receptor type that peaks at only 515 nm. Thus, Viceroys are much less sensitive at long wavelengths than Monarchs. Furthermore, whitish wing spots of the two species have quite different spectra. Calculated tristimulus values indicate that these spots are important signals for species discrimination.

© 1986 Optical Society of America