Iridomyrmex splendens Forel

Heterick, Brian E. & Shattuck, Steve, 2011, Revision of the ant genus Iridomyrmex (Hymenoptera: Formicidae) 2845, Zootaxa 2845 (1), pp. 1-174 : 139-141

Iridomyrmex splendens Forel , stat. n.

( Figs 73 , 96 )

Iridomyrmex mattiroloi splendens Forel, 1907a: 290 .

Iridomyrmex vicina Clark, 1934b: 62 , pl. 4, fig. 22. New synonym.

Types. Iridomyrmex mattiroloi splendens Forel : Syntypes from Donnybrook and Albany, Western Australia ( MHNG, 1 worker, examined; WAMP, 1 worker, examined) ( MCZC holds 1 worker from Mundaring Weir , Western Australia labelled as a type, but this is not true type material). Iridomyrmex vicina Clark : Holotype worker from Beech Forest , Victoria ( MVMA, examined). Paratypes: same data as holotype ( ANIC, ANIC32-017918 , 4 workers, examined; MVMA, 10 workers, 2 queens).

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 0.91–1.24; MTL 0.62–0.76; PpH 0.13–0.17; PpL 0.40–0.51; SI 105–108; SL 0.68– 0.86.

Comments. 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 I. mjobergi and I. meridianus ). In difficult cases, the eye size is often decisive (see ‘Comments’ under I. mjobergi ). Workers usually possess a greenish-yellow or bluish iridescence over the entire body (present only on the gaster in I. 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 I. mattiroloi , it can readily be distinguished from that ant by the longer antenna and the less truncate propodeum. Iridomyrmex 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 . Iridomyrmex vicina becomes a junior synonym of I. splendens in this work. 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).

Figures

FIGURE 73. Iridomyrmex splendens, smaller, dark form (Wrattonbully, SA, ANIC32-023684): A. Front of head; B. Side of body; C. Top of body. Iridomyrmex splendens, larger, pale form (Mount Remarkable, SA, ANIC32-038285): D. Front of head; E. Side of body; F. Top of body; G. Distribution of material examined.

FIGURE 96. Scape length versus head width for I. meridianus, I. mjobergi, I. neocaledonica, I. splendens and I. victorianus.