Army Ant

Army ant is a common name applied to more than 200 ant species across different lineages, unified not by close relation but by a shared aggressive, nomadic lifestyle: massive predatory foraging groups called raids, in which huge numbers of ants hunt simultaneously across a limited area, and an unusual refusal to build permanent nests, with a colony moving almost constantly throughout its existence. This shared behavior, known as legionary behavior, is considered an example of convergent evolution, since several independent lineages arrived at the same basic ecological syndrome. Most New World army ants belong to genera including Eciton, whose species Eciton burchellii is often treated as the archetypal army ant, while most Old World army ants fall within the tribes Aenictini and Dorylini, the latter including the notably aggressive driver ants of the genus Dorylus. Genetic analysis published in 2003 traced several of these lineages to a single common ancestor living around 100 million years ago, near the time Africa and South America separated, although other army ant lineages are still considered to have evolved the behavior independently.