Iridomyrmex splendens

Iridomyrmex splendens is most common in southern Western Australia and south-eastern South Australia (including Kangaroo island), but also occurs in northern Western Australia, Victoria, Tasmania and New South Wales. Throughout much of its range, this is an ant of dry sclerophyll woodland. Nests are commonly found under logs, and workers are often seen foraging on tree-trunks and low vegetation. However, populations of the ant have also been recorded from eucalypt forest near the peaks of some of New South Wales’ higher mountains (e.g., Mt Canobolas, Mt Kaputar and Point Lookout).

Identification
Iridomyrmex splendens is one of about a dozen small-medium variegated brown to black Iridomyrmex that are superficially very similar and, in some cases, sympatric. This species can generally be recognised by the mesosomal vestiture of short, pale, bristly setae and row of short, erect setae on the posterior margin of the head (one or a few randomly distributed setae are present in the very similar Iridomyrmex mjobergi and Iridomyrmex meridianus). In difficult cases, the eye size is often decisive (see Iridomyrmex mjobergi). Workers usually possess a greenish-yellow or bluish iridescence over the entire body (present only on the gaster in Iridomyrmex victorianus, which also has a concave posterior margin of the head, whereas this margin is planar or only weakly indented medially in I. splendens), but may be a bicoloured, variegated brown-and-black or even brown-and-orange. In Tasmania, where I. splendens is sympatric with Iridomyrmex mattiroloi, it can readily be distinguished from that ant by the longer antenna and the less truncate propodeum. The form described as I. vicinus represents the larger, eastern states phenotype of I. splendens, but can readily be associated with the western form by virtue of the small eye, evenly rounded propodeum and appressed and erect pilosity pattern. These features also distinguish these nominal taxa from the very similar I. victorianus.

Distribution based on Regional Taxon Lists
Australasian Region: Australia.

Nomenclature

 *  splendens.  Iridomyrmex mattiroloi var. splendens Forel, 1907h: 290 (w.) AUSTRALIA. Raised to species: Heterick & Shattuck, 2011: 139. Senior synonym of vicinus: Heterick & Shattuck, 2011: 139.
 * vicina. Iridomyrmex vicina Clark, 1934c: 62, pl. 4, fig. 22 (w.q.) AUSTRALIA. Junior synonym of splendens: Heterick & Shattuck, 2011: 139.

Description
Worker Description. Head. Posterior margin of head planar to weakly concave; erect setae on posterior margin in full-face view set in a row; 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 surpassing posterior margin of head by approximately 2 x its diameter. Erect setae on scape absent, except at tip; prominence on anteromedial clypeal margin present as an indistinct swelling or undulation; 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 moderate in number (6–12), short and bristly. Mesonotum sinuous, or straight, or evenly curved. Erect mesonotal setae moderate in number (6–12), short and bristly, or sparse (6 or fewer) 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 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 medium brown to dark blackish-brown, weak yellowish to bluish iridescence on head and body. Colour of erect setae pale yellow to whitish.

Measurements. Worker (n = 5)—CI 84–90; EI 23–29; EL 0.18–0.19; EW 0.14–0.15; HFL 0.80–1.05; HL 0.77–0.92; HW 0.65–0.82; ML 0.9 1–1 .24; MTL 0.62–0.76; PpH 0.13–0.17; PpL 0.40–0.51; SI 105–108; SL 0.68– 0.86.

References based on Global Ant Biodiversity Informatics

 * Borgelt A., and T. R. New. 2005. Pitfall trapping for ants (Hymenoptera, Formicidae) in mesic Australia: the influence of trap diameter. Journal of Insect Conservation 9: 219-221.
 * CSIRO Collection
 * Gibson L. A., and T. R. New. 2007. Characterising insect diversity on Australia's remant native grasslands: ants (Hymenoptera: Formicidae) and beetles (Coleoptera) at Craigieburn Grasslands Reserve, Victoria. Journal of Insect Conservation 11: 409-413.
 * Heterick B. E. 2009. A guide to the ants of south-western Australia. Records of the Western Australian Museum Supplement 76: 1-206.
 * 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.
 * Mann V. 2013. Using insect biodiversity to measure the effectiveness of on-farm restoration plantings. Master of Environmental Management at the School of Geography and Environmental Studies, University of Tasmania 111 pages.
 * Sinclair J. E., and T. R. New. 2004. Pine plantations in south eastern Australia support highly impoverished ant assemblages (Hymenoptera: Formicidae). Journal of Insect Conservation 8: 277-286.