I spent a delightful week in the local mountains leading a generally well-behaved group of Scouts at Camp Tahquitz. One of the Scouts noticed a spot of light near the trail as we hiked back from a campfire in the dark (ah, the virtues of hiking in the dark!). It turns out that they are glow worms (a beetle), most likely California Pink Glowworms (Microphotus angustus)! I was so pleased to find this cousin of the firefly that I hadn't even dreamed of, and right in our back yard.
A little bit of online searching turned up many better photographs than mine as well as more authoritative information. It's hard to believe that that the food habits of this creature are still unknown: What an opportunity for a budding biologist. What I recall from the reading I did is that the glowing ones are actually mature females. The males fly about and don't glow, even though they are still called glow worms.