Iridomyrmex longisoma, Heterick & Shattuck, 2011

Heterick, Brian E. & Shattuck, Steve, 2011, Revision of the ant genus Iridomyrmex (Hymenoptera: Formicidae) 2845, Zootaxa 2845 (1), pp. 1-174 : 96-97

Iridomyrmex longisoma sp. n.

( Fig. 46 )

Types. Holotype worker from Hope Valley , 31°12’30”S 115°47’30”E, Western Australia, 7 May 2006, B. E. Heterick, sclerophyll woodland on white sand ( ANIC, ANIC32-053429 ) . Paratypes: 2 workers, same data as holotype ( ANIC) ; 3 workers from Lancelin , 3101’S 115°20’E, Western Australia, 15 July 2000, M. Jacobs, heathland: white sand ( ANIC, ANIC32-053430 ) ; 6 workers from Stirling Ranges, Gold Holes , Western Australia, c. 250m, 28 October 1969, R. W. Taylor ( ANIC, 2 worker; BMNH, 2 workers; MCZC, 2 workers; ANIC32-041840 ) .

Worker Description. Head. Posterior margin of head strongly convex; erect setae on posterior margin in fullface view set in a row; sides of head straight or weakly convex; erect genal setae present on sides of head in fullface 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 yellowgreen, 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.

Comments. Iridomyrmex longisoma superficially resembles I. 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 I. mayri , an eastern taxon, but lacks the erect hind tibial setae found in that species and its close relatives. This ant is only found in south-western Western Australia, and appears to be confined to the coast. Known nests have been made directly into sandy soil, and are identical to those of I. 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.

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

Figures

FIGURE 46. Iridomyrmex longisoma (paratype, Stirling Range, Gold Holes, WA, ANIC32-041840): A. Front of head; B. Side of body; C. Top of body; D. Distribution of material examined.