Wasmannia auropunctata, commonly known as the Little Fire Ant, is a small pale colored ant that is widely regarded as one of the most harmful introduced ant species in the world. This species has a monomorphic worker caste with 11-segmented antennae, two-segmented antennal club, antennal scrobes, short antennal scapes that do not surpass the posterior margin of the head, a gradually sloped mesosoma, and strong propodeal spines. Like all myrmicines, W. auropunctata has two waist segments and a gaster armed with a stinger.
Diagnosis of worker among Antkey species. Worker caste monomorphic. Head shape roughly ovoid. Antenna 11-segmented. Antennal club 2-segmented. Antennal insertions at least partly covered by frontal lobes;. Antennal scapes not conspicuously short; easily extended beyond eye level; do not extend beyond posterior margin of head. Antennal scrobe present. Eyes medium to large (greater than 5 facets); distinctly less than half head length). Posterolateral corners of head unarmed, without spines. Frontal lobes do not obscure face outline between mandible and eye. Mandibles triangular. Mesosoma with erect hairs. Pronotal spines absent. Propodeum armed with spines or teeth. Slope of mesosoma gradual. Waist 2-segmented. Petiole with a distinct and upright node; pedunculate; lacking large subpetiolar process. Postpetiole attached to lower surface of gaster.
Wasmannia auropunctata is most commonly confused with small yellow species of Tetramorium, such as T. caldarium and T. simillimum. It can be distinguished by the following characters: (1) Antenna 11-segmented (versus 12-segmented); (2) antennal club 2-segmented (versus 3-segmented); (3) propodeal armed with long and robust spines (versus small triangular dents); (4) raised sharp-edged ridge not surrounding antennal insertions (versus present). Additionally, the petiole and petiolar peduncle are shaped differently in W. auropunctata.
Tetramorium caldarium, Tetramorium simillimum