Photonic-Crystal Like Approach to Structural Color of the Earthworm Epidermis

Tsuyoshi Ueta¹*, Yoshihiro Otani² and Naoshi Nishimura²

¹Institute of Media and Information Technology, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan
²Graduate School of Informatics, Kyoto University, Yoshida Honmachi, Sakyo-ku, Kyoto 606-8501, Japan
*E-mail address: tsuyoshi_ueta@jikei.ac.jp

(Received December 3, 2010; Accepted August 16, 2012)

Abstract. The epidermis of an earthworm has a log-pile structure of fibers, and exhibits a structural color. The structure is considered as a photonic crystal. Optical properties of the epidermis of an earthworm have been investigated numerically by means of the analogy of the photonic crystal. The numerical method employed here is the periodic fast multipole method. The structural color is reproduced with the RGB color from the reflection spectrum. The reflection spectrum and the reproduced color are compared with those by a multilayer model and it is confirmed that the treatment as a photonic crystal is important.

Keywords: Earthworm Epidermis, Structural Color, Photonic Crystal, Log-pile Structure, Periodic FMM