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The Sinister Truth Behind Caterpillar Conga Lines

Why do caterpillars line up? What are they plotting?

Let's talk about this video of caterpillars walking in absurd single-file. Is this another case of nature trying to tell us it's time to get off this planet?

There are many videos from people capturing this phenomenon in their own backyards, each narrating with varying degrees of "What the fuck?"

Why do they do this? What are they plotting? How are they so organized?

It's part of the life cycle of Thaumetopoea pityocampa, or pine processionary caterpillar, a species of moth that's native to the Mediterranean region, North Africa and some of the Middle East and southern Europe. Warming winters and climate change are bringing them farther north.


Although they do lay down a sweet line of pheromones as they scoot along, this is not, as one might suspect, a caterpillar fuck-train. They're marching toward a pupation site, where they can bury themselves on the soil and form cocoons. Each caterpillar is drawn forward by the ass of the caterpillar ahead of it. The leader is typically a future female.

As many as three hundred caterpillars have been observed marching in one line like this, according to a blog post written by Terrence D. Fitzgerald, Professor of Biological Science at State University of New York at Cortland.

French entomologist Jean-Henri Fabre studied them extensively, and wrote colorful descriptions of their behavior in his 1916 book, The Life of the Caterpillar:

"They proceed in single file, in a continuous row, each touching with its head the rear of the one in front of it… No Greek theoria winding its way to the Eleusinian festivals was ever more orderly. Hence the name of Processionary given to the gnawer of the pine."

Fabre experimented with their march, arranging them so that they'd walk in a circle, to see how long it would take the "leader" to realize its mistake and correct course. He assumed it would take minutes or hours, but what happened is kind of fucked up: They walked in a circle for a more than a week. "The headless file has no liberty left, no will; it has become mere clock-work," he wrote. Take what you will from that very obvious metaphor for humanity's own futility.

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