Iridomyrmex tenuiceps sp. n.

(Fig. 79)

Types. Holotype worker from Lizard Island, Queensland, 19 February1992, H. Reichel (ANIC, ANIC32-039951). Paratypes: 5 workers, same data as holotype (ANIC, 2 worker; BMNH, 1 workers; MCZC, 2 workers); 2 workers, same data as holotype except 22 February 1992 (ANIC, ANIC32-039953).

Worker Description. Head. Posterior margin of head strongly convex; erect setae on posterior margin absent; sides of head straight or weakly convex; erect genal setae absent from sides of head in full-face view (one to a few small setae may be present near mandibular insertion). Ocelli absent; in full-face view, eyes set at about midpoint of head capsule; in profile, eye set anteriad of head capsule; eye semi-circular, or asymmetrical, curvature of inner eye margin more pronounced than that of its outer margin. Frontal carinae straight; antennal scape surpassing posterior margin of head by 0.2-0.5 x its length. Erect setae on scape absent, except at tip; prominence on anteromedial clypeal margin projecting as triangular spur; mandible elongate triangular with oblique basal margin; long, curved setae on venter of head capsule absent. Mesosoma. Pronotum weakly undulant or almost straight. Erect pronotal setae lacking or very minute (one or two tiny setae may be present). Mesonotum straight. Erect mesonotal setae lacking or very minute (one or two tiny setae present). Mesothoracic spiracles always inconspicuous; propodeal dorsum straight and long (half as long again as length of propodeal declivity); placement of propodeal spiracle mesad, more than its diameter away from propodeal declivity; propodeal angle weakly present or absent, the confluence of the dorsal and declivitous propodeal faces indicated, if at all, by an undulation. Erect propodeal setae lacking or very minute (one or two tiny setae present). Petiole. Dorsum of node convex; node thin, scale-like, orientated anteriad. Gaster. Non-marginal erect setae of gaster present or absent on first gastral tergite; marginal erect setae of gaster present on first tergite, or absent on first tergite. General characters. Allometric differences between workers of same nest absent. Colour grey-brown with coppery sheen, clypeal region and lower genae orange. Colour of erect setae pale yellow.

Measurements. Worker (n = 7) — CI 64–70; EI 40–42; EL 0.25–0.28; EW 0.20–0.21; HFL 1.46–1.74; HL 0.90–1.03; HW 0.60–0.66; ML 1.25–1.39; MTL 1.06–1.22; PpH 0.13–0.15; PpL 0.47–0.53; SI 154–175; SL 1.00– 1.15.

Comments. Iridomyrmex tenuiceps is the sister taxon to I. angusticeps, but is glabrous (see ‘Comments’ under the latter species). Iridomyrmex tenuiceps is widespread across the Torresian zone of Australia (northern Western Australia, Northern Territory and Queensland), and its known range does not extend beyond Australian territories. Specimens have been collected in pitfall traps, but nothing more is known of the ecology of the species.

Etymology. Latin: ‘ tenuis ’ ‘slender’ plus ‘ ceps ’, derivative of ‘ caput ’—‘head’, referring to the slender head of the species.