Most Americans will see some fireworks on July 4, but some animals produce light shows with their bodies all year. These living fireworks light up the night. But how, and why?

These beetles are named for the lights that run down the female’s larva-like body, said to look like lights from train windows at night.

The female’s juvenile-looking form may let her “maintain a bigger store of eggs in a more stable ecosystem, where wings to disperse to another location are not needed,” says Paul Marek, an entomologist at the University of Virginia. Males look more like beetles with fancy “moth antennae and fly wings.”

Only adult female railroad worms and larvae glow. Like many bioluminescent animals their light is created