Iridomyrmex longisoma

Known nests of this species have been made directly into sandy soil, and are identical to those of Iridomyrmex bicknelli. Like the latter ant, I. longisoma seems to favour coastal habitats, including vegetated sand-dunes near the ocean, but is less common. Also, as with I. bicknelli, this is a timorous species.

Identification
Iridomyrmex longisoma superficially resembles Iridomyrmex bicknelli, with which it often occurs. Despite the surface similarities, however, the two ants are probably not closely related: I. longisoma has much longer hind tibiae, hirsute antennal scapes (glabrous in I. bicknelli), an elongate pronotal sclerite, and a broadly rounded occiput (narrowly rounded in I. bicknelli). This species also resembles a small Iridomyrmex mayri, an eastern taxon, but lacks the erect hind tibial setae found in that species and its close relatives.

Distribution
This ant is only found in south-western Western Australia, and appears to be confined to the coast.

Distribution based on Regional Taxon Lists
Australasian Region: Australia.

Nomenclature

 *  longisoma. Iridomyrmex longisoma Heterick & Shattuck, 2011: 96, fig. 46 (w.) AUSTRALIA.

Description
Worker Description. Head. Posterior margin of head strongly convex; 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 at about midpoint of head capsule; in profile, eye set anteriad of head capsule; eye semi-circular. Frontal carinae convex; antennal scape surpassing posterior margin of head by at least 0.5 x its length. Erect setae on scape present and abundant, or present and sparse; 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 absent. Mesosoma. Pronotum weakly undulant or almost straight. Erect pronotal setae numerous (12 or more), short and bristly. Mesonotum sinuous, or straight. Erect mesonotal setae numerous (12 or more), short and bristly. Mesothoracic spiracles always inconspicuous; 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 acuminate; node thick, orientated anteriad. 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 medium to dark chocolate with very weak yellow- green, bluish and/or purple iridescence. Colour of erect setae light brown.

Measurements. Worker (n = 2)—CI 79–80; EI 29–29; EL 0.23–0.24; EW 0.19–0.20; HFL 1.89–1.99; HL 1.01–1.07; HW 0.81–0.85; ML 1.62–1.73; MTL 1.38–1.47; PpH 0.15–0.20; PpL 0.56–0.61; SI 150–153; SL 1.23– 1.30.

Etymology
Latin: longus—‘long’ plus Greek: soma—‘body’

References based on Global Ant Biodiversity Informatics

 * Heterick B. E., and S. Shattuck. 2011. Revision of the ant genus Iridomyrmex (Hymenoptera: Formicidae). Zootaxa 2845: 1-174.