Usage and Circumscription
Historically, "army ant" referred, in the broad sense, to various members of 5 different ant subfamilies: in two of these cases, the Ponerinae and Myrmicinae, it is only a few species and genera that exhibit legionary behavior; in the other three lineages, Ecitoninae, Dorylinae, and Leptanillinae, all of the constituent species are legionary. More recently, ant classifications now recognize an additional New World subfamily, Leptanilloidinae, which also consists of obligate legionary species, and thus is another group now included among the army ants.
A 2003 study of thirty species (by Sean Brady of Cornell University) indicates that the ecitonine and doryline army ants together formed a monophyletic group: all shared identical genetic markers that suggest a common ancestor. Brady concluded that these two groups are therefore a single lineage that evolved in the mid-Cretaceous period in Gondwana, and so the two subfamilies are now generally united into a single subfamily Ecitoninae, though this is still not universally recognized.
Accordingly, the army ants as presently recognized consist of the following genera:
- Subfamily Ponerinae
- Leptogenys (some species)
- Onychomyrmex
- Simopelta
- Subfamily Myrmicinae
- Pheidolegeton
- Subfamily Leptanilloidinae
- Asphinctanilloides
- Leptanilloides
- Subfamily Leptanillinae
- Anomalomyrma
- Leptanilla
- Phaulomyrma
- Protanilla
- Yavnella
- Subfamily Ecitoninae
- Aenictus
- Cheliomyrmex
- Dorylus
- Eciton
- Labidus
- Neivamyrmex
- Nomamyrmex
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