Army ant
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The name army ant (or legionary ant) is applied to over 200 known species, in different lineages, together characterized primarily by their aggressive predatory foraging groups, known as "raids", in which huge numbers of ants all forage simultaneously over a certain area, attacking prey en masse. They also share the habit of not constructing a permanent nest, unlike most ants, and an army ant colony moves almost incessantly over the time it exists. All species are members of the true ant family Formicidae, but there are several groups that have independently evolved the same basic behavioral and ecological syndrome. This syndrome is often referred to as "legionary behavior".
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 thefore a single lineage that evolved in the mid-Cretaceous period in Gondwana[1], and so the two subfamilies are now generally united into a single subfamily Ecitoninae.
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:
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[edit] Ecitoninae
- Most New World army ants belong to the subfamily Ecitoninae, and this is the most commonly-known lineage, therefore bears special mention. This subfamily is further broken into two groups, 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 (Brady, 2003, Tree of Life). 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 Eciton burchellii, whose common name is "army ant" and which is considered to be the archetypal species.
Army ant taxonomy remains ever-changing, and genetic analysis will continue to provide more information about the relatedness of the various species.
[edit] Notes
- ^ BBC News, Dr. David Whitehouse, "Ant history revealed" 10 May 2003.
[edit] External links
Personal website on research and computer modeling of army ants (with video and images):
[edit] References and further reading
- Brady, S. (2003). Evolution of the army ant syndrome: the origin and long-term evolutionary stasis of a complex of behavioral and reproductive adaptations.. PNAS 100(11): 6575-6579.
- Gotwald, W.H., Jr. (1995). Army ants: the biology of social predation. Ithaca, New York: Cornell University Press. ISBN 0-8014-9932-1.
- Rice, Nathan H., and A. M. Hutson (2003). "Antbirds and Army-Ant Swarms", in Christopher Perrins (Ed.): Firefly Encyclopedia of Birds. Firefly Books, 449. ISBN 1-55297-777-3.
- Wilson, Edward O, and Bert Hölldobler, (1990) The Ants (Pulitzer Prize),
