Determination of the cuticle index of the scales of the iridescent butterfly Morpho menelaus

Butterflies of the Morphidae family probably constitute the most popular example of iridescent colours in nature. They present, many fundamental interests in biomimetic processes and can be used as models or sources of inspiration for many industrial applications. The microstructures of the scales are responsible for the coloration, with a major part attributed to interference effects. Their actual optical properties have been described in detail, but the refraction index of the cuticular material is not known with precision. In this paper, we investigate the absolute diffuse reflectivity of the dorsal side of the wings of the species Morpho menelaus. An effective medium theory applied to a multilayer film permits the determination of the anisotropic index of refraction of the cuticle material in the 350-800 nm range. (C) 2003 Elsevier B.V. All rights reserved.