Identification

Key features

The following features distinguish Argentine ants from other species present in New Zealand.

Basic

Small size (2–3 mm)
Light brown in colour (not black, orange/red, yellow)
Workers all same size

Technical characters (a high-powered microscope of 20–40x magnification is needed)

Petiole only one segment (between mesosoma and gaster)
Sting absent
Antennae 12-segmented and without club
Eyes placed low on head with the widest point of head above eyes (to distinguish from Iridomyrmex)
Weakly concave front margin of clypeus
5–8 large teeth on the mandibles
Mandibles longer than wide (to distinguish from Doleromyrma darwiniana; Darwin's ant)
Upper and rear faces of the propodeum equal in length (to distinguish from Doleromyrma darwiniana; Darwin's ant).

Tools

Key to the ants of New Zealand

Body parts mentioned in the key

Field identification

There is no absolute feature that can solely identify Argentine ants in the field. The below features are helpful, but some other ant species also possess these.

Workers are about 2–3 mm long and a uniform light-brown colour (compared with the common black species found foraging in urban areas in New Zealand).
The ants move quite fast (not ponderous).
They walk in defined continuous trails (not erratic ‘crazy’ behaviour of running about in circles)
They have only a slight greasy odour when crushed, as opposed to the strong formic acid smell of some ant species.