An ant mill is an observed phenomenon in which a group of army ants are separated from the main foraging party, lose the pheromone track and begin to follow one another, forming a continuously rotating circle, commonly known as a "death spiral" because the ants might eventually die of exhaustion. It has been reproduced in laboratories and has been produced in ant colony simulations.[1]

An ant mill

The phenomenon is a side effect of the self-organizing structure of ant colonies. Each ant follows the ant in front of it, which works until a slight deviation begins to occur, typically by an environmental trigger, and an ant mill forms.[2] An ant mill was first described in 1921 by William Beebe, who observed a mill 1200 ft (~370 m) in circumference.[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.[4]

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  1. ^ Delsuc F (2003). "Army Ants Trapped by Their Evolutionary History". PLOS Biology. 1 (2): e37. doi:10.1371/journal.pbio.0000037. PMC 261877. PMID 14624241.
  2. ^ Couzin ID & NR Franks (2003). "Self-organized lane formation and optimized traffic flow in army ants". Proceedings of the Royal Society B. 270 (1511): 139–146. doi:10.1098/rspb.2002.2210. PMC 1691225. PMID 12590751.
  3. ^ a b Beebe, William (1921). Edge of the Jungle. New York: Henry Holt and Co. pp. 291–294.
  4. ^ Schneirla TC (1944). "A unique case of circular milling in ants, considered in relation to trail following and the general problem of orientation". American Museum Novitates (1253): 1–26. hdl:2246/3733.

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