A prolonged exposure taken in the darkroom

In some of those examples, bioluminescence is thought to help attract mates, send messages back and forth among members of the same species, or attract prey like in the case of the deep-sea angler fish, which dangles a glowing lure in front of its gaping mouth. Any small fish or other animal following the beacon's glow is gulped up as it approaches the invisible predator hiding in the darkness.Marek and his coworkers hypothesized by using bioluminescence as a warning signal, luminescent millipedes would be attacked less than non-luminescent ones.

Biologists have discovered and described more than 12,000 species of millipedes, but the vast majority remains undiscovered and is thought to number around 100,000. Just like all other millipedes, Motyxia are vegetarians, feeding mostly on decaying plant material, but in the course of adapting to a lifestyle primarily underground, they lost the ability to see.

"They spend the day burrowed beneath the soil and leaf material, but even though they are blind, they somehow sense when night falls, and come to the surface to forage and mate and to go about their millipede business," said Marek, who conducted this work under the NIH Postdoctoral Excellence in Research and Training program in the labs of Wendy Moore, an assistant professor of entomology and curator of the University of Arizona Insect Collection and Dan Papaj, a professor of ecology and evolutionary biology at the University of Arizona.

"When they are disturbed, they ooze toxic cyanide and other foul-tasting chemicals from small pores running along the sides of their bodies as a defense mechanism," Marek explained. "Some millipede species that are active during the day display bright warning colors to announce their defenses to predators, but because Motyxia are out when it's dark, we hypothesized they use their greenish glow in place of a warning coloration."