Monomorium antarcticum

Monomorium antarcticum is an ant of the family Formicidae, endemic to New Zealand. Also known as the southern ant, this is likely New Zealand's most common native ant species. Because it is highly variable in size (3–5mm), colour, and colony structure, it is possible that it consists of a complex of closely related species. It has a generalist diet, including small arthropods, nectar, and seeds, and it also tends aphids, scale insects, and mealybugs to obtain honeydew.

Taxonomy
This species was described by Frederick Smith in 1858 as Atta antarctica, and was placed in the large and extremely diverse genus Monomorium in 1886.

By the early 20th century Monomorium contained 10 subgenera, one of which was Monomorium (Chelaner) Emery, 1914. Chelaner was raised to generic level in 1966 to contain 37 Australian species along with 10 from New Caledonia, New Guinea, and New Zealand.

Bolton in 1987 examined the mophological features of Chelaner, and found them to be too variable to distinguish the genus, which was synonomised with Monomorium again. In 2019 after a comprehensive study of multiple genes the genus Chelaner was resurrected, to house a total of 53 Australasian and Pacific species, including this one, which would then be known as Chelaner antarcticum.

Distribution and habitat
Monomorium antarcticum is endemic to New Zealand, found across the North and South Islands, as well as Stewart Island and smaller offshore islands, the Three Kings Islands, the Chatham Islands, the Kermandec Islands and the Austral Islands.

Monomorium antarcticum are found throughout many habitats including native forest, grasslands, wetlands, pastureland, household gardens as well as horticultural and industrial habitats.

There is some evidence to suggest that the range of Monomorium antarcticum in urban habitats may be restricted due to competition with exotic ant species, at least in northern parts of New Zealand.

Identification
Worker specimens are variable in size, usually 3-5mm in length, with head width varying from 0.60-0.88mm. The antennae have 12 segments, with a three segmented club. Metanotal groove present, either distinctly or weakly impressed. Spines on propodeum are either blunt or absent. Colour highly variable across colonies (but usually consistent within colonies), from orange, light to dark brown and black.