Hiroshi TABATA,¹ Kinya KUMAZAWA,¹ Masami FUNAKAWA,¹ Jun-ichi TAKIMOTO^1,3_[footnote] and Makio AKIMOTO²

¹Social and Advanced Research Laboratory, Nissan Motor Co., Ltd., 1, Natsushima-cho, Yokosuka, 237 Japan, ²Department of Pharmacology, Nippon Medical School, 1-1-5, Sendagi, Bunkyo-ku, Tokyo, 113 Japan

(Received November 4, 1995; Accepted January 11, 1996)

This paper describes the mechanism generating the beautiful wing colors of various male butterflies and the relationship between the wing material and the color appearance. The microstructure of the scales covering the upper surface of the wings was analyzed with the aid of a scanning electron microscope. The basic mechanism of color generation of structurally colored scales is determined for the first time in accordance with the theory of optical interference in thin film layers using a model of wing scales. Optical properties were found in relation to the three-dimensional spectral reflectance of the samples, and differences were observed between the brightness perceived in subjective evaluations and calculated values based on the reflective spectra of the structurally colored wings. The results of this study suggest that the microroughness of the upper wing surface may influence the perceived gloss of structurally colored wings.

Key words : butterfly wing, microstructure, lamella, anisotropic color, optical interference, structural color, three-dimensional reflective spectra

^*Present address: Department of Materials Science and Engineering, Yamagata University, 4-3-16, Jonan, Yonezawa, 992 Japan.