Most New World army ants belong to the subfamily Ecitoninae. This subfamily is further broken into two groups in the New World, the tribes Cheliomyrmecini and Ecitonini. The former contains only the genus Cheliomyrmex, and the tribe Ecitonini contains four genera, Neivamyrmex, Nomamyrmex, Labidus, and Eciton, the genus after which the group is named. The genus Neivamyrmex is the largest of all army ant genera, containing some 120 species, all in the United States. The most predominant species of Eciton is E. burchellii, whose common name is "army ant" and which is considered to be the archetypal species.
The Old World army ants are divided between the two tribes Aenictini and Dorylini (often treated as Dorylini alone), each of which is made up of a single genus; in the former case, Aenictus, that contains over 100 species of army ant, while the Dorylini contains the aggressive "driver ants" in the genus Dorylus, of which there are some 70 species known.
Army ant taxonomy remains ever-changing, and genetic analysis will continue to provide more information about the relatedness of the various species; many genera contain large numbers of taxa at the rank of subspecies (e.g., Dorylus, in which some 60 of roughly 130 named taxa are only considered subspecies at present).