[Image above] Cyphochilus beetles are whiter than white. Credit: Wild Center; Flickr CC BY-NC 2.0
There are some bizarre bugs in the world.
One particularly interesting specimen is an über white beetle native to southeast Asia called the Cyphochilus beetle—this beetle is whiter than the whitest white paint, plastics, and paper we humans can manufacture.
New research shows that the secret to the beetles’ color lies in the optical properties of their scales, which are made of a material called chitin. Chitin makes up mollusk shells, fungi cell walls, and bug exoskeletons, and it’s functionally similar to keratin, the stuff that makes up our hair and nails.
The research, a collaboration between the University of Cambridge (United Kingdom) and the European Laboratory for Non-Linear Spectroscopy (Italy), set out to examine just how the beetles achieve their white color—which indicates that the material reflects all wavelengths of light—despite the low refractive index of chitin.
“Current technology is not able to produce a coating as white as these beetles can in such a thin layer,” says lead researcher Silvia Vignolini. “In order to survive, these beetles need to optimize their optical response, but this comes with the strong constraint of using as little material as possible in order to save energy and to keep the scales light enough in order to fly.”
The researchers measured how light propagated in the bugs’ scales and found that their chitin scatters light “more efficiently than any other low-refractive-index material yet known,” states the release. According to the paper’s abstract, that’s due to “a remarkably optimized anisotropy of intra-scale chitin networks, which act as a dense scattering media.”
“These scales have a structure that is truly complex since it gives rise to something that is more than the sum of its parts,” says co-author Matteo Burresi of the Italian National Institute of Optics in Florence. “Our simulations show that a randomly packed collection of its constituent elements by itself is not sufficient to achieve the degree of brightness that we observe.”
The researchers hope their insight will help to develop whiter stuff that uses less materials, reducing waste and generating lighter finished products.
The open-access paper, published in Scientific Reports, is “Bright-white beetle scales optimise multiple scattering of light” (DOI:10.1038/srep06075).