Iridomyrmex hertogi, Heterick & Shattuck, 2011

Heterick, Brian E. & Shattuck, Steve, 2011, Revision of the ant genus Iridomyrmex (Hymenoptera: Formicidae) 2845, Zootaxa 2845 (1), pp. 1-174 : 88-90

Iridomyrmex hertogi sp. n.

( Figs 41 , 94 )

Types. Holotype worker from Kakadu National Park, Arnhem escarpment near Round Jungle , Northern Territory, July 1993, H. Reichel ( ANIC, ANIC32-047828 ) . Paratypes: 1 worker, same data as holotype ( ANIC) .

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 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 present as an indistinct swelling or undulation; mandible regularly triangular with oblique basal margin; long, curved setae on venter of head capsule absent. Mesosoma. Pronotum moderately and evenly curved over its length. Erect pronotal setae lacking or very minute (one or two tiny setae may be present). Mesonotum evenly curved. Erect mesonotal setae lacking or very minute (one or two tiny setae present). Mesothoracic spiracles always inconspicuous; propodeal dorsum straight and short (equal in length to propodeal declivity); placement of propodeal spiracle posteriad and near propodeal declivity, or 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 lacking or very minute (one or two tiny setae present). Petiole. Dorsum of node convex; node thin, scale-like, orientation more-or-less vertical. Gaster. Non-marginal erect setae of gaster absent on first gastral tergite; marginal erect setae of gaster present on first tergite, or absent on first tergite. General characters. Allometric differences between workers of same nest absent. Colour dark grey-brown. Colour of erect setae whitish (clypeus and coxae).

Measurements. Worker (n = 2) — CI 85–86; EI 36–37; EL 0.18–0.19; EW 0.14–0.15; HFL 0.53–0.55; HL 0.59–0.60; HW 0.51–0.51; ML 0.71–0.72; MTL 0.40–0.40; PpH 0.11–0.11; PpL 0.29–0.29; SI 87–90; SL 0.44– 0.46.

Comments. Iridomyrmex hertogi appears to be confined to the Northern Territory, and is only known from one collection. This very small species can be confused with two other sympatric Iridomyrmex , most notably, the small northern workers of I. mjobergi . However, the antennal scape is very short in I. hertogi , barely attaining the posterior margin of the head, or falling short of it (SI ≤ 90) (exceeding the posterior margin of head by at least its width in I. mjobergi (SI ≥ 90)), and the antennal scape is distinctly lighter in colour than the head capsule (approximately the same colour in I. mjobergi ). The mesosoma is also glabrous (generally with a few to several erect setae in small, northern I. mjobergi ). A second species, I. difficilis , is readily differentiated from I. hertogi by the latter’s much larger eye (EI ≈ 0.30 versus EI <0.30) and by the appearance of the antennal scape, which is noticeably lighter in colour than the head capsule in I. hertogi (approximately the same colour in I. difficilis ). Iridomyrmex hertogi however, appears to have as its nearest relative another very small Iridomyrmex ; I. niger , known only from much further south, is almost identical in morphology and can only be separated on the basis of its larger size and smaller eye (i.e., EI 31–33, compared with EI 36–37 in I. hertogi , and HL of 0.62–0.76mm and HW of 0.59–0.60mm compared with HL of 0.59–0.60mm and HW of 0.51mm in I. hertogi ). Nothing is known about the habits or ecology of I. hertogi .

Etymology. Named in honour of Mr Tony Hertog (TERC) who first alerted our attention to this species.

Figures

FIGURE 41. Iridomyrmex hertogi (holotype, Kakadu National Park, NT, ANIC32-047828): 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.