Iridomyrmex azureus

The distribution of this ant includes some of the driest habitat in Australia, most collections being taken in far inland South Australia and Western Australia. The species also occurs in New South Wales and the Northern Territory.

Identification
Because of its bluish or purplish iridescence, the brownish-red I. azureus would most easily be confused with Iridomyrmex roseatus or a small meat ant when seen in the field. However, unlike I. roseatus or meat ants, I. azureus lacks erect setae on its antennal scapes and tibiae.

Distribution based on Regional Taxon Lists
Australasian Region: Australia.

Nomenclature

 *  azureus. Iridomyrmex bicknelli var. azureus Viehmeyer, 1914b: 41 (w.) AUSTRALIA. Raised to species: Heterick & Shattuck, 2011: 48.

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 noticeably 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). Number of ocelli two, or ocelli absent; in full-face view, eyes set above 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 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 moderately and evenly curved over its length. Erect pronotal setae moderate in number to numerous (6 or more), short and bristly. 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 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), short and bristly. 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 present. Colour foreparts medium to dark reddish-brown with weak to moderate bluish or pinkish iridescence, legs brown, gaster dark brown to black with greenish-yellow to purple or pink iridescence. Colour of erect setae pale, whitish.

Measurements. Worker (n = 5)—CI 81–87; EI 24–27; EL 0.25–0.27; EW 0.19–0.21; HFL 1.98–2.24; HL 1.17–1.32; HW 0.94–1.15; ML 1.66–1.88; MTL 1.47–1.68; PpH 0.20–0.23; PpL 0.61–0.65; SI 134–151; SL 1.40– 1.55.

References based on Global Ant Biodiversity Informatics

 * Baroni Urbani C. 1977. Katalog der Typen von Formicidae (Hymenoptera) der Sammlung des Naturhistorischen Museums Basel (2. Teil). Mitt. Entomol. Ges. Basel (n.s.) 27: 61-102.
 * Heterick B. E., and S. Shattuck. 2011. Revision of the ant genus Iridomyrmex (Hymenoptera: Formicidae). Zootaxa 2845: 1-174.
 * Shattuck S. O. 1994. Taxonomic catalog of the ant subfamilies Aneuretinae and Dolichoderinae (Hymenoptera: Formicidae). University of California Publications in Entomology 112: i-xix, 1-241.
 * Taylor R. W., and D. R. Brown. 1985. Formicoidea. Zoological Catalogue of Australia 2: 1-149.
 * Viehmeyer H. 1914. Neue und unvollständig bekannte Ameisen der alten Welt. Archiv für Naturgeschichte (A)79(12): 24-60.