Iridomyrmex anderseni

This distinctive species is known from only a single specimen collected in eastern South Australia. Nothing is known of its biology.

Identification
A member of the viridigaster complex with the following characteristics: in lateral profile, posterior region of pronotum strongly arched, central region weakly convex; scapes and dorsum of gaster without erect hairs; HL > 1.39 mm, SL > 1.02 mm.

Worker diagnosis of the viridigaster complex of the calvus group: petiole moderately to strongly inclined anteriorly but with a distinct anterior face; propodeum expanded dorsally into a uniform to weakly angular convex arch; central projection of anterior clypeal margin posterior to, or less commonly even with, an imaginary line drawn between the anterior-most points of the medio-lateral convexities; overall body size generally larger than in the calvus complex (HW > 1.07 mm, PnL + ML + PpL > 1.80 mm, HTL > 1.30 mm). Medium to large, reddish species of the southern arid zone of Australia.

Worker diagnosis of the calvus species group: frontal carinae curved throughout their entire length and are never sinuate. An apparently related species group containing I. vicinus Clark is superficially similar to the I. calvus group, but has the frontal carinae arched posteriorly and anteriorly and approximately straight medially, rather than being arched throughout their length.

Distribution based on Regional Taxon Lists
Australasian Region: Australia.

Nomenclature

 *  anderseni. Iridomyrmex anderseni Shattuck, 1993b: 1310, figs. 22, 23, 38 (w.) AUSTRALIA. See also: Heterick & Shattuck, 2011: 43.

Description
Worker Description. Head. Posterior margin of head 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 full-face view. Ocelli absent; in full-face view, eyes set above 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 failing to attain posterior margin of head. Erect setae on scape absent, except at tip; prominence on anteromedial clypeal margin present as an indistinct swelling or undulation; mandible regularly triangular with oblique basal margin; long, curved setae on venter of head capsule present. Mesosoma. Pronotum strongly inclined anteriorly. 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 prominent as small, vertical protuberances; propodeal dorsum protuberant; 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 sparse to absent. 'Petiole. 'Dorsum of node planar; node thin, scale-like, orientation more-or-less vertical. Gaster. Non-marginal erect setae of gaster absent on first gastral tergite; marginal erect setae of gaster absent on first tergite. General characters. Allometric differences between workers of same nest absent. Colour head, mesonotum propodeum and legs reddish brown, pronotum orange, gaster dark chocolate.

Measurements. Worker (n = 1)—CI 95; EI 24; EL 0.32; EW 0.18; HL 1.40; HW 1.33; ML 0.55; PpH 0.23; PpL 0.75; SI 77; SL 1.03.

References based on Global Ant Biodiversity Informatics

 * Shattuck S. O. 1993. Revision of the Iridomyrmex calvus species-group (Hymenoptera: Formicidae). Invertebrate Taxonomy 7: 1303-1325.