Most wasps are most active in the morning and slow down considerably at midday, when the sun's heat is most oppressive. Not so oriental hornets, who build nests underground: their workers do more digging the more they're bombarded with sunlight. That's probably because, as researchers at Tel Aviv University revealed, nanostructures in the insect's exoskeleton form a kind of solar cell, harvesting light energy that could power the hornet's work.
In the brown section of the hornet's abdomen, the layers of cuticle that make up the exoskeleton are embossed with grooves about 160 nanometers high. The grooves are arranged into a sort of grating, which helps trap the light that hits the hornet and bounce it around within the cuticle. The yellow section, which has small, interlocking protrusions about 50 nanometers high, also absorbs light--and the researchers showed that xanthoperin, the pigment that gives it its yellow color, can be used to convert light into electricity. It's likely doing just that inside the insect, which would explain why they're busiest when it's sunniest--and why, as a previous study found, anesthetized Oriental hornets wake up faster when they're pounded with UV light.