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. 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. Each ant follows the ant in front of it, and this will work until something goes wrong and an ant mill forms.
A unique case of circular milling in ants, considered in relation to trail following and the general problem of orientation. by Schneirla, T. C. (3.8 Mb)
Figure 800 - MC Escher's Moebius Ring with Ants (ref.)