Ant mill

An ant mill is an observed phenomenon in which a group of army ants, separated from the main foraging party, lose the pheromone track and begin to follow one another, forming a continuously rotating circle.

This circle is commonly known as a "death spiral" because the ants might eventually die of exhaustion.

[1] The phenomenon is a side effect of the self-organizing structure of ant colonies.

[3] It took each ant two and a half hours to make one revolution.

[3] Similar phenomena have been noted in processionary caterpillars and fish.