The beetle family Phengodidae is known also as glowworm beetles, whose larvae are known as glowworms. The females and larvae have bioluminescent organs. They occur throughout the New World from extreme southern Canada to Chile. The family Rhagophthalmidae, an Old World group, used to be included in the Phengodidae.
Larval and larviform female glowworms are predators, feeding on millipedes and other arthropods occurring in soil and litter. The winged males, which are often attracted to lights at night, are short-lived and probably do not feed. Females are much larger than the males and are completely larviform. Males may be luminescent, but females and larvae have a series of luminescent organs on trunk segments which emit yellow or green light, and sometimes an additional head organ which emits red light, as in railroad worms.
This family is distinct from the fireflies (family Lampyridae), which may also be called "glow-worms" in its larval stage. It also apparently includes the long-lipped beetles, which are only differentiated from phengodids by the unusual modifications of their mouthparts – it appears that Phengodidae is paraphyletic if the long-lipped beetles were treated as a family Telegeusidae.A luminescent larva or female