Circular milling is a strange phenomenon wherein army ants follow each other around in circles again and again until they become exhausted and die – en masse.
From the Ant Room:
This is one of my favorite things about ants — the ant death spiral. Actually, it’s a circular mill, first described in army ants by Schneirla (1944). A circle of army ants, each one following the ant in front, becomes locked into a circular mill. They will continue to circle each other until they all die. How crazy is that? Sometimes they escape, though. Beebe (1921) described a circular mill he witnessed in Guyana. It measured 1200 feet in circumference and had a 2.5 hour circuit time per ant. The mill persisted for two days, “with ever increasing numbers of dead bodies littering the route as exhaustion took its toll, but eventually a few workers straggled from the trail thus breaking the cycle, and the raid marched off into the forest.”
I’ve yet to see an ant death spiral in real life, but now that I know that they happen… I’ll be looking.
Circular milling in action
Circular milling on a smaller scale
