Photonic Crystal Structure and Coloration of Wing Scales of Butterflies Exhibiting Selective Wavelength Iridescence.

Filip Mika,Suratwadee Jiwajinda,Jiřina Matějková-Plšková,Punyavee Dechkrong,Makoto Shiojiri

doi:10.3390/ma5050754

Abstract

The coloration of butterflies that exhibit human visible iridescence from violet to green has been elucidated. Highly tilted multilayers of cuticle on the ridges, which were found in the scales of male S. charonda and E. mulciber butterflies, produce a limited-view, selective wavelength iridescence (ultraviolet (UV)~green) as a result of multiple interference between the cuticle-air layers. The iridescence from C. ataxus originates from multilayers in the groove plates between the ridges and ribs. The interference takes place between the top and bottom surfaces of each layer and incoherently between different layers. Consequently, the male with the layers that are ~270 nm thick reflects light of UV~560 nm (green) and the female with the layers that are ~191 nm thick reflects light of UV~400 nm (violet). T. aeacus does not produce the iridescent sheen which T. magellanus does. No iridescent sheen is ascribed to microrib layers, which are perpendicular to the scale plane, so that they cannot reflect any backscattering. The structures of these butterflies would provide us helpful hints to manipulate light in photoelectric devices, such as blue or UV LEDs.

Highlights

Characteristic patterns and the vivid coloration of the wing scales of butterflies have lately attracted considerable attention as natural photonic crystals
We have investigated the coloration in different areas in the wings of a male Euploea mulciber (E. mulciber) butterfly [11], and male and female Chrysozephyrus ataxus (C. ataxus) butterflies [14]
Wing scales of several butterflies exhibiting selective wavelength iridescence from violet to green were investigated by Scanning electron microscopy (SEM) and optical reflectance measurement

Summary

Introduction

Characteristic patterns and the vivid coloration of the wing scales of butterflies have lately attracted considerable attention as natural photonic crystals. Lawrence et al [9] reported in 2002 that the T. magellanus uses pigment coloration at all but a narrow tailored range of angles, where multilayered rib-like (or microrib) scales cause the characteristic effect, adding a blue-green sheen that had been known in only one other species of butterfly. It was the A. meliboeus [8,9]. It is dwelt on why human eyes observe only the limited iridescent hues from such butterflies as E. mulciber, S. charonda and C. ataxus

Samples and Methods

Highly Tilted Multilayers of Cuticle on the Ridges

Multilayered Microribs

Conclusions