The glowing millipedes of Alcatraz Island

Millipedes, that glow. Just one of the critters that lives on the famous Alcatraz Island that we had no idea about until recently. They were discovered last year during a survey of the island's rat population. While most people are interested in the prison buildings and the history of the inescapable island, other visitors have their eyes on the animal life, including the seabirds like pelicans, cormorants and egrets, and you know, glowing bugs.
The millipedes were discovered last February as researchers used black lights in their work identifying the scale of rat populations. KQED writes, "To identify rats, National Park Service staff routinely place bait in feeding stations. The bait is laced with a non-toxic fluorescent dye that ends up in urine stains and feces. Surveyors later scan the grounds at nighttime with black light. The more glowing they observe, the larger they extrapolate the rat population to be. A recent February search turned up no evidence of rats. Instead, surveyors were surprised to discover millipedes glowing intensely white."
The millipedes were not just glowing because they'd munched on rat bait. Researchers checked samples of millipedes from the same scientific family, and sure enough, they glowed too.
As it turns out, while these are the first recorded millipedes that glow found on Alcatraz, there are other millipede species that have similar sci-fi abilities. Seven species of millipede can emit light from their bodies like fireflies to warn predators away. All of these species are only found in California, and no where else in the world.
Yet, the millipede species discovered on Alcatraz is unlike these others. Rather than emitting a glow like a firefly, it has a fluorescence like that found in scorpions, that only shows up (to our eyes, anyway) with a tool like a black light. This is the only species of millipede ever known to glow in this sort of way, which makes it fascinating to researchers. Researchers at UC Davis are working on figuring out just what makes this millipede glow, and hope to have publishable answers by this summer.
Meanwhile, even the species of millipedes that emit their own glow remain a bit of a mystery. Scientists don't quite know how they manage such a trick. Live Science reports, "The reason why these millipedes glow is a mystery. They are blind, adapted to a lifestyle primarily spent underground, so they cannot use their glow to send messages to other members of their species. Also, while deep-sea angler fish dangle glowing lures in front of their mouths to attract prey, Motyxia are vegetarians just like all other millipedes, feeding mostly on decaying plant material. so they have no need to pull in victims. Still, a number of poisonous millipede species active during the day are thought to display bright colors to warn predators that they possess toxins and to steer clear. Since Motyxia are instead out in the dark, [researcher Paul Marek, an evolutionary biologist at the University of Arizona] and his colleagues reasoned 'they use their greenish glow in place of a warning coloration,' he said."