Iridomyrmex obsidianus

Identification
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 Iridomyrmex calvus, which is also found on New Caledonia.

Distribution based on Regional Taxon Lists
Australasian Region: New Caledonia.

Nomenclature

 *  obsidianus. Iridomyrmex obsidianus Emery, 1914f: 419, pl. 13, fig. 13 (w.) NEW CALEDONIA. See also: Shattuck, 1993b: 1319; Heterick & Shattuck, 2011: 116.

Description
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.

References based on Global Ant Biodiversity Informatics

 * Baroni Urbani C. 1977. Katalog der Typen von Formicidae (Hymenoptera) der Sammlung des Naturhistorischen Museums Basel (2. Teil). Mitt. Entomol. Ges. Basel (n.s.) 27: 61-102.
 * CSIRO Collection
 * Emery, C. 1914. Les fourmis de la Nouvelle-Calédonie et des îles Loyalty. Nova Caledonia. A. Zoologie 1:393-437.
 * Heterick B. E., and S. Shattuck. 2011. Revision of the ant genus Iridomyrmex (Hymenoptera: Formicidae). Zootaxa 2845: 1-174.
 * Heterick, B., and S. O. Shattuck. "Revision of the ant genus Iridomyrmex (Hymenoptera: Formicidae)." Zootaxa 2845 (2011): 1-174.
 * Jennings J. T., L. Krogmann, and C. Burwell. 2013. Review of the hymenopteran fauna of New Caledonia with a checklist of species. Zootaxa 3736(1): 1-53.
 * Shattuck S. O. 1993. Revision of the Iridomyrmex calvus species-group (Hymenoptera: Formicidae). Invertebrate Taxonomy 7: 1303-1325.
 * Shattuck S. O. 1994. Taxonomic catalog of the ant subfamilies Aneuretinae and Dolichoderinae (Hymenoptera: Formicidae). University of California Publications in Entomology 112: i-xix, 1-241.
 * Taylor R. W. 1987. A checklist of the ants of Australia, New Caledonia and New Zealand (Hymenoptera: Formicidae). CSIRO (Commonwealth Scientific and Industrial Research Organization) Division of Entomology Report 41: 1-92.
 * Wheeler W.M. 1935. Check list of the ants of Oceania. Occasional Papers of the Bernice Pauahi Bishop Museum 11(11):1-56.
 * Wheeler, W. M. 1927. The ants of Lord Howe Island and Norfolk Island. Proc. Am. Acad. Arts Sci. 62: 121-153
 * Wheeler, William Morton. 1927. The Ants of Lord Howe Island and Norfolk Island. Proceedings of the American Academy of Arts and Sciences 62(4): 121-153
 * Wheeler, William Morton.1935.Checklist of the Ants of Oceania.Occasional Papers 11(11): 3-56