Scientists Now Know Why Thousands Of Millipedes Mysteriously Swarmed Japanese Train Lines

It’s 1920 and an exciting landmark moment has been reached in Japan: the opening of a new train line near its thriving capital, Tokyo. A locomotive works its way high into the mountains and into a densely forested area, beset by trees and shadows. But one day the train on this new route is stopped in its tracks by the strangest of obstacles: a swarm of ghostly white creepy-crawlies swamping the rails. The arthropods would disappear not long after, but not forever, returning every eight years or so in an enduring mystery that has only recently been solved.

Millipedes on Honshu

The millipedes live on Honshu, which is the largest of Japan’s four main islands. As it turns out, they regularly cross the Hokuriku, Koumi and Chuo lines, which between them link some of Japan’s most important cities. These lines also pass through the mountains at the island’s center, where they’ve been reporting millipede-related delays on and off for a century.

Fall invasion

Millipede invasions tend to happen in the fall, and for the brief period when they arrive it becomes impossible for the trains to move. Although they’re barely more than an inch long, when the millipedes rise from the earth in their thousands the swarm can span more than 650 feet. There’s nothing you can do but wait for them to pass.

Special defense

It’s not just the numbers that are off-putting for train drivers. These millipedes are Japanese natives known as Parafontaria laminata armigera and they have their own special defense. You might associate cyanide with Agatha Christie novels, but this potentially lethal poison is also how these millipedes repel predators.

Until they simply vanish

So there you have it: every so often thousands of ghostly white millipedes with bodies containing lethal toxins cover every inch of train tracks, nearby roads and the surrounding forest. Then they just disappear into the soil and under dead leaves. As strangely as they appear they vanish again and trains can finally resume their journeys. But why? What’s the reason?