Iridomyrmex hesperus

Iridomyrmex hesperus is an uncommon member of the viridigaster complex. For other details of its distribution and biology see Shattuck (1993).

Identification
This ant is confined to Western Australia and can be distinguished from other members of the complex by its lack of iridescence, its hairy mesosoma, the presence of erect setae on the hind tibiae and its relatively elongate antennal scape.

Distribution based on Regional Taxon Lists
Australasian Region: Australia.

Nomenclature

 *  hesperus. Iridomyrmex hesperus Shattuck, 1993b: 1316, figs. 24, 25, 38 (w.) AUSTRALIA. See also: Heterick & Shattuck, 2011: 90.

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 present on sides of head in full- face view. 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. Frontal carinae concave; antennal scape surpassing posterior margin of head by 1– 2 x its diameter. 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 moderately and evenly curved over its length. Erect pronotal setae numerous (12 or more), short and bristly. Mesonotum straight. Erect mesonotal setae numerous (12 or more), short and bristly. Mesothoracic spiracles always prominent as small, vertical protuberances; propodeal dorsum protuberant; placement of propodeal spiracle mesad, more than its diameter away from 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), short and bristly. Petiole. Dorsum of node convex; node thick, 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. Colour anterior of head capsule and mesosoma pale orange with some brown infuscation, head, gaster and legs brown. Colour of erect setae yellowish brown.

Measurements. Worker (n = 3)—CI 91–92; EI 27–28; EL 0.30–0.31; EW 0.17–0.17; HL 1.18–1.23; HW 1.08–1.13; ML 0.53–0.58; PpH 0.20–0.23; PpL 0.69–0.74; SI 89–91; SL 0.98–1.03.