Iridomyrmex obsidianus Emery

Heterick, Brian E. & Shattuck, Steve, 2011, Revision of the ant genus Iridomyrmex (Hymenoptera: Formicidae) 2845, Zootaxa 2845 (1), pp. 1-174 : 116-117

Iridomyrmex obsidianus Emery

( Figs 59 , 87 , 88 )

Iridomyrmex obsidianus Emery, 1914: 419 , pl. 13, fig. 13.

Types. Syntypes from Mt. Humboldt , 1600 m, New Caledonia ( MCSN, 1 worker, examined; NHMB, 1 worker, Baroni Urbani, 1977) .

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 concave; antennal scape surpassing posterior margin of head by approximately 3 x its diameter. Erect setae on scape absent, except at tip; prominence on anteromedial clypeal margin always completely absent; mandible triangular with distinct angle between masticatory and basal margins; 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 straight. Erect mesonotal setae lacking or very minute (one or two tiny setae present). Mesothoracic spiracles always prominent as small, vertical protuberances; propodeal dorsum protuberant; placement of propodeal spiracle posteriad and near 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 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 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 shining dark chocolate. Colour of erect setae pale yellow.

Measurements. Worker (n = 3) — CI 86–93; EI 25–25; EL 0.18–0.21; EW 0.12–0.13; HL 0.85–0.90; HW 0.73–0.84; ML 0.39–0.42; PpH 0.13–0.13; PpL 0.42–0.51; SI 107–119; SL 0.87–0.90.

Comments. The extremely shiny cuticle and rather long antennal scape (surpassing the posterior margin of the head by approximately 3 x its diameter) enable this ant to be distinguished readily from I. calvus , which is also found on New Caledonia. For other details see Shattuck (1993b) .

Figures

FIGURE 59. Iridomyrmex obsidianus (Mount Dzumac, New Caledonia, ANIC32-007293): A. Front of head; B. Side of body; C. Top of body; D. Distribution of material examined.

FIGURE 87. Scape length versus head width for I. anderseni, I. calvus and I. obsidianus.

FIGURE 88. Head length versus head width for I. anderseni, I. calvus and I. obsidianus.