Railroad worms are not actually worms. Despite their appearance, they’re not caterpillars, either. Most of them are beetle larvae, but some of the aren’t – we’ll get back to that in a minute.
Also known as “glowworms,” railroad worms are named for the bioluminescent sections on the sides of their bodies look like train car windows when they light up at night. How cute! They’re little arthropod trains; someone needs to make them into transportation for tiny forest dwellers in a fantasy novel or something.
Apart from the “windows,” railroad worms can also make their heads glow red, which is thought to help them see better at night and scare off predators. Both the yellow and red lights are created using luciferin and luciferase, the same molecules and enzymes fireflies use to make their lower abdomens glow.
As cute as their name is, we really ought to call them “railroad larvae,” because most railroad worms are actually larvae of beetles in the Phrixothrix genus of the family Phengodidae. However, female railroad worms never metamorphose into beetles and retain their larval features throughout their lives, so you could run into some Phrixothrix “larvae” that aren’t actually larvae at all! When railroad worm males grow up, however, they trade their glowing windows for a sick pair of feathery antlers, I mean, antennae:
The best time to find a railroad worm is at night or after a rainstorm when they come out to hunt for food. During the day, these colorful, shimmering insects typically spend their time snoozing in the dirt or hanging out on tree trunks, if you’re searching for railroad worms in a lazier mood.
It can also be easy to mistake railroad worms for colorful millipedes in the daylight. Unlike millipedes, however, railroad worms are insects and only have six legs as compared to a millipede’s hundreds – in fact, they actually eat millipedes! Railroad worms also eat a ton of other garden pests, too, so it’s always a good sign to see one crawling around your tomato plants.
…Why does everyone have tomato plants? Why do we always talk about tomato plants when we talk about home gardens? We never talk about blueberries or squash or cabbage…
Well, all that to say that it’s a good sign when you see railroad worms around your zucchini and boysenberries, too.