Railroad worm

A railroad worm is a larva or larviform female adult of a beetle of the genus Phrixothrix in the family Phengodidae, characterized by their unique possession of two different colors of bioluminescence. The luminescent organs of their body can glow green, while those on their head can glow red; this is probably due to different luciferases in their bodies, as the reaction substrate, called luciferin, is the same. This is believed to be an adaptation to help confuse and frighten predators.

The term "railroad worm" is also sometimes applied to the Apple maggot.