Iridomyrmex adstringatus sp. n.

(Fig. 7)

Types. Holotype worker from Coolatoo, Coorong, South Australia, 12 October 1975, P. J. M. Greenslade (ANIC, ANIC32-042656). Paratypes: 1 worker from Salt Creek, Coorong, South Australia, 11 November 1972, P. J. M. Greenslade (ANIC, ANIC32-042658); 1 worker from 5km W Mt. Rough, Coorong-Keith, South Australia, 25 October 1972, P. J. M. Greenslade (MCZC, ANIC32-042657).

Worker Description. Head. Posterior margin of head planar to weakly concave; erect setae on posterior margin in full-face view set in a row; sides of head noticeably convex; erect genal setae present on sides of head in fullface view. Ocelli absent; in full-face view, eyes set at about midpoint of head capsule; in profile, eye set anteriad of head capsule; eye asymmetrical, curvature of inner eye margin more pronounced than that of its outer margin. Frontal carinae concave; antennal scape barely attaining posterior margin of head, or surpassing it by less than 1 x its diameter. Erect setae on scape present and abundant; prominence on anteromedial clypeal margin present as an indistinct swelling or undulation; mandible elongate triangular with oblique basal margin; long, curved setae on venter of head capsule present. Mesosoma. Pronotum moderately and evenly curved over its length. Erect pronotal setae moderate in number (6–12), longest setae elongate, flexuous and/or curved. Mesonotum straight. Erect mesonotal setae moderate in number (6–12), short and bristly. Mesothoracic spiracles always prominent as small, vertical protuberances; propodeal dorsum smoothly and evenly convex; placement of propodeal spiracle posteriad and near propodeal declivity; propodeal angle present as a bluntly defined right angle, the dorsal and declivitous propodeal faces never separated by a carina. Erect propodeal setae numerous (12 or more) and elongate, flexuous and/or curved. Petiole. Dorsum of node convex; node thin, scale-like, orientated anteriad. Gaster. Non-marginal erect setae of gaster present on first gastral tergite; marginal erect setae of gaster present on first tergite. General characters. Allometric differences between workers of same nest absent. Colour frons, upper genae, legs and gaster brown, mesosoma and legs mainly orange with some darker, brownish areas.

Measurements. Worker (n = 2)—CI 91-92; EI 28-29; EL 0.23-0.25; EW 0.18-0.21; HFL 0.92-1.00; HL 0.90- 0.94; HW 0.82-0.87; ML 1.22-1.26; MTL 0.69-0.73; PpH 0.18-0.18; PpL 0.53-0.53; SI 84-85; SL 0.69-0.74.

Comments. Iridomyrmex adstringatus is a close relative of I. calvus characterised by its small size (HW ≤ 0.85mm), hairy mesosoma and hind tibiae and matte sculpture. As with a number of other species related to I. calvus, I. adstringatus is rare and has only been collected in South Australia. Most specimens have come from the Coorong district.

Etymology. Latin: ‘ adstringatus ’ meaning ‘compressed’ or ‘drawn together’, referring to the chunky, compact appearance of the worker.