The biggest colonies in the Western Hemisphere are over one million ants.  Theses are subterranean colonies of Labidus.  The biggest colonies of the large swarm raider, Eciton burchellii are about 700,000.  The biggest colonies of the African Driver Ants range from 20 to 24 million.  This web site does not discuss the Eastern Hemisphere army ants in the subfamily Dorylinae.  All the information below pertains to the Western Hemisphere subfamily Ecitoninae.

Largest bivouac of Eciton burchellii foreli we have found estimated to have 700,000 ants