They occur throughout the New World from extreme southern Canada to Chile, numbering over 250 species in total.

[2] The recently recognized members of the Phengodidae, the Cydistinae, are found in Western Asia.

Larval and larviform female glowworms are predators, feeding on millipedes and other arthropods occurring in soil and litter.

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.

Some early studies suggested that Phengodidae might possibly include (or be sister taxon to) the long-lipped beetles,[3] which were formerly treated as a family Telegeusidae, but these are now treated as a subfamily within the family Omethidae.