Iridomyrmex spurcus

The habitat of this species is invariably arid or semi-arid, all records coming from well away from the coast. The ant also has a large range, having been recorded from all Australian states except Victoria and Tasmania. Iridomyrmex spurcus nests in soil, but will forage on trees, one series having being taken in a yellow pan trap. Other ecological data are lacking.

Identification
This small-medium sized Iridomyrmex has much the same appearance as many workers of Iridomyrmex omalonotus but the erect setae on the mesosomal dorsum, antennal scapes and legs are distinctly longer, and the ant is very hairy overall.

Distribution based on Regional Taxon Lists
Australasian Region: Australia.

Nomenclature

 *  spurcus.  Iridomyrmex gracilis subsp. spurcus Wheeler, W.M. 1915g: 813 (w.) AUSTRALIA. Raised to species: Heterick & Shattuck, 2011: 142 (not stated).

Description
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 straight or weakly 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, or 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 convex; antennal scape surpassing posterior margin of head by 0.2–0.5 x its length. Erect setae on scape present and abundant; prominence on anteromedial clypeal margin projecting as blunt but distinct protuberance; mandible regularly triangular with oblique basal margin; long, curved setae on venter of head capsule absent. Mesosoma. Pronotum moderately and evenly curved over its length. Erect pronotal setae numerous (12 or more) and longest setae elongate, flexuous and/or curved. Mesonotum straight. Erect mesonotal setae numerous (12 or more) and elongate, flexuous and/or curved. 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 numerous (12 or more) and elongate, flexuous and/or curved. Petiole. Dorsum of node convex; node thin, scale-like, orientation more-or-less vertical. 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 uniformly brown. Colour of erect setae pale, whitish.

Measurements. Worker (n = 3)—CI 88–90; EI 26–30; EL 0.19–0.21; EW 0.16–0.17; HFL 0.94–1.16; HL 0.72–0.88; HW 0.64–0.79; ML 0.96–1.19; MTL 0.70–0.88; PpH 0.13–0.16; PpL 0.40–0.50; SI 122–124; SL 0.79– 0.98.

References based on Global Ant Biodiversity Informatics

 * Heterick B. E. 2009. A guide to the ants of south-western Australia. Records of the Western Australian Museum Supplement 76: 1-206.
 * Heterick B. E., and S. Shattuck. 2011. Revision of the ant genus Iridomyrmex (Hymenoptera: Formicidae). Zootaxa 2845: 1-174.