Iridomyrmex lividus

Identification
The range of I. lividus overlaps with the closely related Iridomyrmex purpureus. In general, fresh worker material can be distinguished by its dark colour and strong blue iridescence. However, faded specimens can be quite difficult to separate from western samples of I. purpureus, in particular. The rather more angulate form of the propodeum in most I. lividus is a helpful character (this sclerite is more rounded in many I. purpureus), but must be used with caution as it is not universal. In the field, the small, single entrance hole to the I. lividus nest contrasts with the large mound made by its close relative.

Distribution based on Regional Taxon Lists
Australasian Region: Australia.

Biology
Biochemically, this ant shares the frequencies of several allozyme alleles with those of I. purpureus (Halliday, 1979, 1981) although there are differences in competitive abilities between the two species (Greenslade, 1987).

Nomenclature

 *  lividus. Iridomyrmex lividus Shattuck, 1993a: 125, fig. 12 (w.) AUSTRALIA. See also: Heterick & Shattuck, 2011: 94.

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 above midpoint of head capsule; in profile, eye set anteriad of head capsule; eye semi-circular. Frontal carinae convex; antennal scape surpassing posterior margin of head by approximately 2 x its diameter. Erect setae on scape present and abundant; prominence on anteromedial clypeal margin projecting as triangular spur; mandible elongate 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 numerous (12 or more), short and bristly. Mesonotum sinuous. Erect mesonotal setae numerous (12 or more), short and bristly. Mesothoracic spiracles always prominent as small, vertical protuberances; propodeal dorsum protuberant; placement of propodeal spiracle posteriad and near propodeal declivity, or mesad, more than its diameter away from propodeal declivity; propodeal angle present as a bluntly defined right angle, the dorsal and declivitous propodeal faces never separated by a carina, or 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 acuminate; node thick, 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 head, appendages and mesosoma reddish-brown to blackish-brown with blue or purple iridescence, gaster chocolate to black with variable blue, greenish, pink or purple iridescence. Colour of erect setae brown.

Measurements. Worker (n = 31)—CI 87–99; EI 17–22; EL 0.31–0.38; EW 0.19–0.23; HL 1.75–2.15; HW 1.58–2.12; ML 0.77–1.02; PpH 0.23–0.38; PpL 0.82–1.13; SI 85–101; SL 1.51–1.84.

References based on Global Ant Biodiversity Informatics

 * CSIRO Collection
 * Heterick B. E., and S. Shattuck. 2011. Revision of the ant genus Iridomyrmex (Hymenoptera: Formicidae). Zootaxa 2845: 1-174.
 * Shattuck S. O. 1993. Revision of the Iridomyrmex purpureus species-group (Hymenoptera: Formicidae). Invertebrate Taxonomy 7: 113-149.