The Origin of the Iridescent Colors in Coleopteran Elytron

Takahiko Hariyama¹*, Yasuharu Takaku², Mantaro Hironaka^1,3, Hiroko Horiguchi¹, Yoshiaki Komiya⁴ and Masashi Kurachi⁴

¹Laboratory of Biology, Hamamatsu University School of Medicine, 1-20-1 Handayama, Hamamatsu 431-3192, Japan
²National Institute of Genetics, Mishima, Shizuoka 411-8540, Japan
³Department of Applied Biological Sciences, Faculty of Agriculture, Saga University, Saga 840-8502, Japan
⁴Department of Molecular and Cellular Neurobiology, Gunma University School of Medicine, 3-39-22 Shouwa-machi, Maebashi 371-8511, Japan
*E-mail address: hariyama@hama-med.ac.jp

(Received April 29, 2002; Accepted August 1, 2002)

Keywords: Coleoptera, Optical Thickness, Epicuticle, Exocuticle, Structural Color

Abstract. The physical mechanisms responsible for the wide variation of metallic color within a single species, Plateumaris sericea, were investigated by the structural observations and the spectral analysis of the reflected light. The surface of elytra consisted of epicuticle and exocuticle, both having high and low refractive index layers. Only the epicuticle had the understandable optical thicknesses of approximately one-quarter of the wavelength of the light. The results of theoretical analysis were compared with the measured spectral reflections.