Nocturnal millipedes in the genus Motyxia glow in the dark. But why? Being blind, they’re not lighting up to impress one another. Scientists collected 164 millipedes from Giant Sequoia National Monument in California and painted half of them to conceal their light. They also created 300 clay millipedes, half painted with a luminescent pigment. They left the millipedes out overnight and found “carnage” the next day, says University of Arizona entomologist Paul Marek. Dark millipedes, whether real or fake, were attacked by rodents more than twice as often as their glowing counterparts. The greenish blue light appears to serve as a defense mechanism, warning predators away, like a skull and crossbones: These millipedes produce a cyanide toxin that predators do well to avoid.