Other Common Names
Legionary Ants, Driver Ants (names more often used for Old World army ants)
Synonyms and other taxonomic changes
used to be treated as a separate subfamily Ecitoninae
3 genera north of Mexico: Labidus, Nomamyrmex each with a single species, Neivamyrmex with ~2 dozen spp.
workers 2-18 mm; queens, males 9-30+ mm
Workers superficially similar to Myrmicinae, because of 2-segmented waist and general habitus.
Differ as follows:
eyes small, reduced to one or a few indistinct facets
antennal scapes short (significantly less than the head length), thick, especially apically - in life, antennae constantly and rapidly in motion
antennal bases close together separated by only a narrow rearward extension of the clypeus that blends insensible into the narrow frons.
huge, wingless queens and wasplike males unlike those of any other ants
Males are so different from workers that there are concurrent taxonomies for the two castes, in which males and workers that have not yet been associated have different names. (DNA promises to resolve some of this excess)
Southern USA, Neotropics, 2 spp. north to Virginia, Iowa, n. California
Nests impermanent, in pre-existing subterranean chambers, stumps, logs, rock piles.
mostly brood of other ants, with varying degrees of prey species specialization
These have cyclic reproduction and foraging. Large, synchronized batches of eggs are laid by the huge queens during a period of relatively low colony activity, during which pupae grown from the previous batch of eggs also mature. Larvae hatch simultaneously with the eclosion of the new brood of adults, initiating a period of very active predation and nearly daily relocation to a new nest site. In North American species, a sexual brood of a few permanently wingless virgin queens and a few dozen males is produced at the end of summer, and the brood cycle is suspended during the winter months.
North American army ants are nocturnal, except in cool or heavily overcast weather, so are not often seen, though in some cases relatively abundant. They forage along fast-moving, anastomosing trails, harvesting brood from ant nests, often with little or no damage to the adult population (a sustainable harvest).
Army ant queens cannot fly for dispersal because they do not have wings. They also have a very low reproduction rates through colony fission and depend on high native ant populations to feed on. This means they are particularly susceptible to habitat fragmentation and local extinctions by roads and human activity.