Or if you prefer the more technical term:
An ant mill is a phenomenon where a small 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. The ants will eventually die of exhaustion. This has been reproduced in laboratories and the behaviour has also been produced in ant colony simulations. This phenomenon is a side effect of the self-organizing structure of ant colonies.
An ant mill was first described by William Beebe who observed a mill 1,200 feet (365 m) in circumference. It took each ant 2.5 hours to make one revolution.
Reminds me of the long-term effects of epistemic closure.
(Hat tip: Nerdcore)