Iridomyrmex spodipilus Shattuck

Heterick, Brian E. & Shattuck, Steve, 2011, Revision of the ant genus Iridomyrmex (Hymenoptera: Formicidae) 2845, Zootaxa 2845 (1), pp. 1-174 : 141-142

Iridomyrmex spodipilus Shattuck

( Fig. 74 )

Iridomyrmex spodipilus Shattuck, 1993a: 139 , fig. 18.

Types. Holotype worker from 21km WNW of William Creek , 28°49'S 136°09'E, South Australia ( ANIC, ANIC32- 009173 , examined) . Paratypes: same data as holotype ( ANIC, ANIC32-009174 , 28 workers, examined; BMNH, 3 workers; MCZC, 3 workers) .

Worker Description. Head. Posterior margin of head strongly concave; erect setae on posterior margin in fullface 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. Frontal carinae convex; antennal scape surpassing posterior margin of head by 1–2 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 absent. 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 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 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 head and mesosoma reddish with very pale blue, greenish or yellow iridescence, legs light brown, gaster black with bluish-green iridescence. Colour of erect setae pale, ashy brown.

Measurements. Worker (n = 25) — CI 86–95; EI 19–24; EL 0.34–0.41; EW 0.18–0.24; HL 1.65–2.07; HW 1.44–1.90; ML 0.74–1.00; PpH 0.23–0.38; PpL 0.75–1.05; SI 87–102; SL 1.48–1.71.

Comments. Iridomyrmex spodipilus is the only southern member of the I. sanguineus complex, and, like I. spadius , also occurs in two disjunct populations. In general appearance, this species strongly resembles a very large I. discors , with which it shares pale, erect setae on its body parts. However, under a microscope its long anteromedian clypeal prominence, its higher scape index and its overall dimensions are sufficient to easily separate it from I. discors . As with I. discors , iridescence is weak to absent in this species, but where it occurs it is pink to purple. In his study of the I. purpureus species-group, Shattuck (1993a) mentions differences between I. spodipilus populations occurring in South Australia and those occurring in Queensland and New South Wales. South Australian workers are lighter in overall colour and head and mesosoma do not vary, whereas eastern workers are darker with the head lighter than the mesosoma. Workers of the latter are also slightly smaller on average than those of the former. Shattuck considered these differences to be intraspecific.

Specimens from Fowlers Gap, New South Wales, have been collected in low shrub and grassland, which presumably this ant favours. Otherwise there are no ecological data.

Figures

FIGURE 74. Iridomyrmex spodipilus (holotype, William Creek, SA, ANIC32-009173): A. Front of head; B. Side of body; C. Top of body; D. Distribution of material examined.