Really interesting article in Science this week on a species of beetle with unbelievably white scales.
(You see how I make with the funny in my headline?)
Apparently Cyphochilus beetles, found in Southeast Asia, have evolved coloration that lets them hide among white fungus. Now usually animal color comes from pigmentation or carefully arranged structures (or both). Neither of those is very good for appearing white, because to look white something has to scatter every wavelength of visible light equally.
But these beetles have scales just 5 microns thick that act as three-dimensional photonic solids—materials that manipulate light. Internally the scales are "a random network of interconnecting cuticular filaments," the article says. It's the randomness that does the job, apparently. Those filaments (in conjunction with the air gaps between them, says a good summary on Scientific American's web site today) bounce light around just right to have whiteness and brightness comparable to human baby teeth and treated paper.
Getting a synthetic material to be white, bright, and opaque is one of the bases of the international pigmentation industry. So it's no surprise that the press release from Exeter University, where the principal investigator of the study's located (Pete Vukusik) plays up the possible biomimetic uses of these beetle scales.
