The animal kingdom boasts many an impressive form, from arching giraffe necks to spoon-shaped bird beaks to gigantic beetle claws. But evolution has worked on much smaller scales too, producing finely honed nanostructures--parts less than a millionth of a meter across, or smaller than 1/20th of the width of a human hair--that help animals climb, slither, camouflage, flirt, and thrive.
Consider an insect's compound eye, which has anywhere from 50 to 10,000 individual facets, each with its own set of optical machinery. Zoom in on the seemingly smooth curves of those facets and, in many insects--like the robber fly seen here--you'll find they're studded with an array of nanoscale protuberances called "corneal nipples." The tiny bumps, which range in diameter from 50 to 300 nanometers, help the insects camouflage: by breaking up the cornea's even surface, they cut down the glare that reflects off the eye, which could potentially alert a predator to the bug's presence. The nanoscale nipple pattern on moth eyes has inspired new anti-reflective coatings for solar cells.
In 2010, German scientists discovered another useful function of corneal nipples: they help keep pollen grains, dust particles, and other microscopic crud out of the insects' eyes. The bumpy texture means less contact area for a small particle to cling onto, so even when the rest of the bugs' bodies get grimy, the eyes stay clean.