Iridomyrmex exsanguis

In the field, I. exsanguis appears to have a similar behaviour to Iridomyrmex dromus. Both ants are timid, and may block up their nests during the day. A small pile of spoil gives away the nest position. In Western Australia, B. Heterick has found both species in sandy soil, particularly on dunes. Despite its generally nocturnal disposition, this species can be diurnally active in suitable conditions: at Hillston, New South Wales, Rev. Bede Lowery was able to attract the species to honey baits on mallee stems at 8 am in the morning.

Identification
Worker specimens of I. exsanguis can be hard to distinguish from those of Iridomyrmex dromus; the primary, and often the only distinguishing feature being the more truncate appearance of the propodeum in I. exsanguis. Lack of erect hind tibial setae distinguish it from Iridomyrmex cupreus and Iridomyrmex macrops, and the moderately abundant to abundant short, bristly, erect setae on the mesosomal dorsum easily separate it from Iridomyrmex hartmeyeri. Most workers are a depigmented yellow and of small-medium size, but workers taken in the far Kimberley are larger and darker coloured.

Distribution
In places like Carnarvon, Western Australia, nests of I. exsanguis and I. dromus can occur adjacent to one another. However, I. exsanguis has a slightly more restricted distribution than its sister taxon I. dromus, and has rarely been collected south of latitude 30°S in Western Australia (although it has been collected as far south as 32 km N of Renmark, South Australia).

Distribution based on Regional Taxon Lists
Australasian Region: Australia.

Nomenclature

 *  exsanguis. Iridomyrmex exsanguis Forel, 1907h: 296 (w.q.) AUSTRALIA. Crawley, 1922c: 26 (m.). See also: Heterick & Shattuck, 2011: 80.

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. 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 its outer margin and anterior sector of eye distinctly broader than its posterior sector. Frontal carinae concave, or 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 present as an indistinct swelling or undulation; mandible elongate triangular with oblique basal margin; long, curved setae on venter of head capsule present in some workers. Mesosoma. Pronotum moderately and evenly curved over its length. Erect pronotal setae moderate in number (6–12), short and bristly. Mesonotum evenly curved. Erect mesonotal setae sparse to absent. Mesothoracic spiracles always inconspicuous; propodeal dorsum straight and short (equal in length to propodeal declivity); 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 moderate in number (6–12), 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 absent. Colour pale, depigmented yellow, more rarely, brownish-yellow. Colour of erect setae pale yellow.

Measurements. Worker (n = 5)—CI 84–93; EI 36–39; EL 0.23–0.35; EW 0.16–0.24; HFL 0.95–1.48; HL 0.71–1.04; HW 0.60–0.97; ML 0.94–1.41; MTL 0.65–1.02; PpH 0.12–0.21; PpL 0.37–0.57; SI 110–125; SL 0.75– 1.07.