They've got fireflies back east but glow-in-the-dark bugs are a rarity here in the Bay Area. Or are they? That depends. If you pick up a UV flashlight (also known as a black light) and go out to a park or your backyard you'll probably spot one of these guys, it's a millipede called the Xystocheir dissecta and I saw this one in El Cerrito hills near my house. (By the way, the video wasn't altered, it's actually what I saw!)
They come out in the fall and winter and forage through the detritus under oak trees. You can find the Xystocheir dissecta all over the Bay Area. These millipedes fluoresce, which means that chemicals in their skin absorb the invisible UV light and then re-emit the energy as visible light.
According to Paul Marek, a researcher at University of Arizona, another species of millipede, Motyxia sequoiae, is truly bioluminescent, which means they glow in the dark even without a UV light shining on them, just like a firefly. These are found in the southern Sierra Nevada mountains and in Sequoia National Park.
By the way, if you're a serious bug hobbyist, you should check out Marek's project he's trying "to collect all described species of xystodesmid millipede in the United States. Specimens will be photographed, color measured with a spectrometer, and DNA and RNA archived."