ant mill

{{Short description|Phenomenon in which a group of ants march in a continuously rotating circle}}

{{Redirects|Ant Spiral|the Lemon Demon song, "Spiral of Ants"|Spirit Phone}}

File:Ant mill.gif

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. It has been reproduced in laboratories and in ant colony simulations.{{cite journal|vauthors=Delsuc F |year=2003 |title=Army Ants Trapped by Their Evolutionary History| journal=PLOS Biology|volume=1|issue=2|page=e37 |doi=10.1371/journal.pbio.0000037 |pmid=14624241 |pmc=261877 |doi-access=free }}

The phenomenon is a side effect of the self-organizing structure of ant colonies. Each ant merely follows the ant in front of it, which functions until a slight deviation begins to occur, typically by an environmental trigger, and an ant mill forms.{{cite journal|author=Couzin ID & NR Franks|title=Self-organized lane formation and optimized traffic flow in army ants|journal=Proceedings of the Royal Society B |year=2003 |volume=270 |pages=139–146 |doi=10.1098/rspb.2002.2210|pmid=12590751|issue=1511|pmc=1691225}} An ant mill was first described in 1921 by William Beebe, who observed a mill 370 m in circumference. It took each ant two and a half hours to make one revolution.{{cite book |last=Beebe |first=William |url=https://books.google.com/books?id=ArMZAAAAYAAJ&pg=PA291 |title=Edge of the Jungle |publisher=Henry Holt and Co. |year=1921 |location=New York |pages=291–294}} Similar phenomena have been noted in processionary caterpillars and fish.{{cite journal| vauthors=Schneirla TC| title=A unique case of circular milling in ants, considered in relation to trail following and the general problem of orientation| journal=American Museum Novitates |year=1944| issue=1253| pages=1–26 |hdl=2246/3733}}