Polyrhachis

Within its range, Polyrhachis is one of the more common groups of ants. They nest in open soil or in soil under rocks and logs, in holes in standing trees and a few tropical species form arboreal nests made of plant fibres (carton) and larval silk. Most of the ground nesting species form inconspicuous nests but at least one in arid Australia (the mulga ant, P. macropa) forms large mounds decorated with dried leaves. Polyrhachis also contains the only known marine ants in the world. The species P. constricta and P. sokolova nest in mangrove mud flats which are subject to tidal flooding. They retreat into their nests as the tide advances, foraging in mangroves only during low tide when their nests are exposed.

Species are omnivorous and will collect nectar. Most are fairly timid and will retreat when disturbed. Some of the arboreal species will bang their bodies against the walls of their nests when disturbed, producing a distinct, loud rattling noise. Many are nocturnal, especially in arid areas, while others forage during the day.



Worker of P. andromache from Queensland.



Worker of P. glabrinotum from Queensland.



Worker of P. hermione from Queensland.



Worker of P. yorkana from Queensland.

Identification
The area above the hind leg is smooth and lacks an opening (the metapleural gland opening). The mandibles have at most 7 teeth. The scale of the petiole is upright and has an angular or rounded top which almost always has two or more teeth or strong angles (a few species have only week angles). The upper plate of the first segment of the gaster (first gastral tergite) is relatively long and covers more than one-half the total length of the gaster. Spines or teeth are usually present on the mesosoma but sometimes the mesosoma is smooth.

Polyrhachis is one of the larger groups of ants in Australia and most species are easily recognised. The majority are black, moderately large (5 to 10 mm in total length), and have spines or ridges on the mesosoma and spines on the top of the petiole. Some species (in the subgenus Cyrtomyrma) differ in having the upper surface of the mesosoma highly arched and lacking spines or angles. These species, however, have teeth or strong angles present on the top of the petiole. Additionally, all species of Polyrhachis have the first upper plate of the gaster elongate and comprising more than one-half the total length of the gaster.

Distribution and Habitats
Australian distribution

Regional Species Lists

 * Australia

Keys to Species

 * Australia