The white-footed house ant (Technomyrmex albipes) is an introduced species in New Zealand. These foraging ants are searching for food for the colony, which can easily be traced along the trail. This species was first documented in Nelson in 1921 and is now well established both indoors and outside in warmer northern parts of the country. In southern New Zealand it appears to be restricted to indoors. Ants that invade houses are more likely to be introduced, rather than native species.
Argentine ants (Linepithema humile) are one of around 28 introduced ant species in New Zealand. They are very aggressive and can eliminate other ant colonies, and also destroy and eat other insect species and earthworms. These invasive species pose a great threat to many forest floor invertebrates that have evolved in a land without aggressive ant species. Although they breed prolifically, Argentine ants do not fly but walk to establish new nests. This means that they do not spread rapidly, but an infested site has a very high number of ants and colonies which merge into one vast super-colony that extends over a very large area. Their natural rate of invasion is a few hundred metres per year.
The Southern ant (Monomorium antarcticum) is the most common. This species shows a lot of variation, and it is uncertain whether it is a single species or a complex of several species. Workers are about 3–4 millimetres long, and can range in colour from orange with darker markings to entirely black. They live in almost all habitats: forest, grassland, dry river beds, sphagnum bogs, rotting logs, and suburban gardens and lawns. They also forage along the shore or high in the mountains. This species is known to gather and store plant seeds. Nests range from small to well populated, with thousands of workers.
The Striated ant (Huberia striata) is slightly larger than the southern ant, and workers range from reddish yellow to black. This one is also abundant and lives in similar habitats to the southern ant. In some nests, a large number of shells of a small native land snail have been found. It is thought that the ants capture live snails and bring them into the nest, where they feed on them. The colonies can hold hundreds of thousands of workers. Both the southern and striated ants are found in close association with sap-sucking bugs (some species of the insect suborder Homoptera), which they milk for their sweet excreta.
The largest native ants are Pachycondyla castanea and P. castaneicolor, the biggest workers of which are over 6 millimetres long. These reddish brown ants have a strong sting. While more at home in native bush and forest, they have also been found in urban areas.
The native ant Amblyopone saundersi and the closely related, introduced Australian Amblyopone australis are rather sluggish ants, which make only small nests of up to a few hundred individuals. They hunt underground or in enclosed spaces such as rotting wood and leaf litter. They sting to paralyse or kill insects and other arthropods, and feed the partially dismembered bodies to their larvae. While they can inflict a painful sting on humans, they are not aggressive