Ant death spiral

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.
Ant Death Spiral (Via Cynical-C)