Structural light absorption in elytral micropillars of Euprotaetia inexpectata beetles

Abstract

Structural absorption is reported to be responsible for the deep black appearance of numerous living organisms, including butterflies, birds, and spiders. Here, we report the presence of structural absorption in the beetle Euprotaetia inexpectata, which has reflectivity values as low as 0.1% and absorptivity values as large as 99.5%. By combining ultrastructural studies and full-wave optical simulations, we show that the black appearance of this beetle is generated by arrays of anisotropic micropillars, which enhance absorptivity through a combination of optical focusing and Mie scattering. These results highlight the independent evolution of black surfaces in nature and provide interesting templates for bio-inspired applications.