A railroad worm is a larva or larviform female adult of a beetle of the genus Phrixothrix in the family Phengodidae, characterized by the possession of two different colors of bioluminescence. It has the appearance of a caterpillar. The eleven pairs of luminescent organs on their second thoracic segment through their ninth abdominal segment can glow yellowish-green, while the pair on their head can glow red;

The "railroad worm" name arises because these glowing spots along the body resemble the windows of train cars internally illuminated in the night.

References

  • |Frederico G. C. Arnoldi, Antonio Joaquim da Silva Neto, & Vadim R. Viviani. (2010). Molecular insights on the evolution of the lateral and head lantern luciferases and bioluminescence colors in Mastinocerini railroad-worms (Coleoptera: Phengodidae). Photochemical & Photobiological Sciences, 9(1), 87–92. https://doi.org/10.1039/B9PP00078J