Iridomyrmex niger, Heterick & Shattuck, 2011

Heterick, Brian E. & Shattuck, Steve, 2011, Revision of the ant genus Iridomyrmex (Hymenoptera: Formicidae) 2845, Zootaxa 2845 (1), pp. 1-174 : 112-113

Iridomyrmex niger sp. n.

( Figs 56 , 94 )

Types. Holotype worker from 2km S Ravine des Casoars, Kangaroo Island , South Australia, 11 January 1973, P. J. M. Greenslade ( ANIC, ANIC32-037336 ) . Paratypes: 1 worker from N of Breakneck River , South Australia, January, 1973, P. J. M. Greenslade ( ANIC, ANIC32-037335 ) ; 1 worker from Victor Harbor , South Australia, 10-11 November 1973, P. J. M. Greenslade ( ANIC, ANIC32-037223 ) ; 1 worker from 15km ENE Cranbrook , Tasmania, 41°57’S 148°14’E, 28 January 1983, I. D. Naumann & J. C. Cardale, ex ethanol ( MCZC, ANIC32-042211 ) ; 1 worker from Kabarli E ( Cooloola ), Queensland, 22 April 1976, P. J. M. Greenslade ( BMNH, ANIC32-037262 ) .

Worker Description. Head. Posterior margin of head planar to weakly concave; erect setae on posterior margin absent; 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). 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, or asymmetrical, curvature of inner eye margin more pronounced than that of its outer margin. Frontal carinae straight; antennal scape barely attaining posterior margin of head, or surpassing it by less than 1 x its diameter. Erect setae on scape absent, except at tip; prominence on anteromedial clypeal margin always completely absent; 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 lacking or very minute (one or two tiny setae may be present) or present as short bristles. Mesonotum evenly curved. Erect mesonotal setae lacking or very minute (one or two tiny setae present) or present as short bristles. Mesothoracic spiracles always inconspicuous; propodeal dorsum protuberant; placement of propodeal spiracle posteriad and near 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 lacking or very minute (one or two tiny setae present) or present as short bristles. Petiole. Dorsum of node planar; node thick, orientation more-or-less vertical. Gaster. Non-marginal erect setae of gaster present or absent on first gastral tergite; marginal erect setae of gaster may be absent from first tergite. General characters. Allometric differences between workers of same nest absent. Colour dark brown to black, sometimes with bluish iridescence. Colour of erect setae on coxae, clypeus yellowish-brown.

Measurements. Worker (n = 5)—CI 84–86; EI 31–33; EL 0.17–0.21; EW 0.13–0.16; HFL 0.64–0.73; HL 0.62–0.76; HW 0.53–0.65; ML 0.78–0.99; MTL 0.48–0.55; PpH 0.10–0.14; PpL 0.31–0.40; SI 90–96; SL 0.51– 0.60.

Comments. This minute, grey-black to bluish Iridomyrmex (HW ≈ 0.5mm) is most reminiscent of I. coeruleus , but the anterior clypeal margin lacks a distinct prominence or spur. Workers are minute and among the smallest Iridomyrmex , only the morphologically identical I. hertogi (Northern Territory) being consistently smaller (see discussion under that species). The ant is found from south-east South Australia to southern Queensland, but relatively few specimens are known. A worker from Wyperfeld NP was collected in a malaise trap in mallee with a Leptospermum understory, suggesting that the species will forage on low vegetation.

Etymology. Latin: ‘black’.

Figures

FIGURE 56. Iridomyrmex niger (Coorong-Keith, Bunbury, SA, ANIC32-037334): A. Front of head; B. Side of body; C. Top of body; D. Distribution of material examined.

FIGURE 94. Head length versus head width for I. hertogi and I. niger.