Railroad-worms routinely feed on millipedes that are as large or larger than they are, including the colorful American giant millipede, which can be up to 4 inches long. Millipedes are formidable prey because of their heavily armored bodies and the fact that many millipedes exude noxious chemicals when they are threatened, with different groups of millipedes producing different types of defensive chemicals. Larvae and females are specialized predators of millipedes. Perhaps the strangest thing about railroad-worms is what they eat and how they catch it. The unusually large plumose antennae are the most distinctive feature they are almost half the length of the body and branched like a fern frond. Male glowworms have wings, but the front pair, the elytra, which form that hard protective covering on most beetles, are reduced to stubs, making the translucent, membranous hind wings more visible. Though very different from females, males are equally odd and unbeetle-like.

Males find females by using their unusually large antennae to sense pheromones produced by the females. Why do they glow? Unlike fireflies, which use their lights both to find mates and to warn potential predators they are toxic or distasteful, glowworms use their lights primarily as a warning, much like the warning coloration of Monarch butterflies.

They got the name “railroad-worm because a large larva or female crawling about at night somewhat resembles a distant passenger train with lights glowing through the windows. The greenish-yellow glow is continuous, with spots of light on most body segments and bands of light emanating from between the segments. All stages of these insects glow, even the eggs and pupae, but large larvae and mature females are most impressive. Railroad-worms are also called glowworms because they glow in the dark, again a trait they share with fireflies, though they belong to a different family of beetles. Female railroad worms remain “larviform” after they become sexually mature, a trait they share with some species of fireflies, which despite their name, are also beetles. In fact, she looks just like she did as a larva, except for being larger (about 3 inches). Notice she has no wings and looks very unbeetle-like. That’s a mature female beetle in the photo. Railroad-worms are some of the strangest insects in the country.

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