Iridomyrmex angusticeps Forel

Heterick, Brian E. & Shattuck, Steve, 2011, Revision of the ant genus Iridomyrmex (Hymenoptera: Formicidae) 2845, Zootaxa 2845 (1), pp. 1-174 : 44

Iridomyrmex angusticeps Forel

( Fig. 12 )

Iridomyrmex angusticeps Forel, 1901: 19 .

Types. Syntype workers from Rabaul (as Ralum), Papua New Guinea ( NHMB, one headless worker, examined (images provided by www.anttypes.org)) .

Worker Description. Head. Posterior margin of head weakly convex; erect setae on posterior margin in fullface view set in a row, or present in small aggregations on one or both sides of posterior margin of head; sides of head straight or weakly convex; erect genal setae present on sides of head in full-face view. Ocelli absent; in fullface view, eyes set at about midpoint of head capsule; in profile, eye set anteriad of head capsule; eye elongate, 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 0.2-0.5 x its length. Erect setae on scape absent, except at tip; 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 weakly undulant or almost straight. Erect pronotal setae numerous (12 or more), short and bristly. Mesonotum straight. Erect mesonotal setae moderate in number (6-12), short and bristly, or sparse to absent. Mesothoracic spiracles always inconspicuous; propodeal dorsum straight and long (half as long again as length of propodeal declivity); 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 moderate in number (6-12), 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 brown to grey-brown. Colour of erect setae pale brownish-yellow.

Measurements. Worker (n = 4) — CI 66-69; EI 39-41; EL 0.26-0.31; EW 0.20-0.23; HFL 1.50-1.88; HL 0.98- 1.16; HW 0.66-0.78; ML 1.36-1.67; MTL 1.10-1.31; PpH 0.14-0.19; PpL 0.51-0.66; SI 161-171; SL 1.08-1.26.

Comments. This species is one of the few Iridomyrmex that can be found outside of Australasia: at least two pins in ANIC were collected on the Island of Mindanao, in the Philippines. Other collections have been made in Papua New Guinea and also in northern regions of Queensland, Northern Territory and Western Australia. Of the more common Iridomyrmex , this species most resembles I. bicknelli , but the head is much narrower in relation to its length (CI 66-69 versus 74-78 in I. bicknelli ). The nearest close relative appears to be I. tenuiceps , but I. angusticeps has minute, bristly, white, erect setae on the mesosomal dorsum, and these are lacking in the glabrous I. tenuiceps . The Philippines workers were collected in pineapple fields while Australian material has been collected in rainforest and Acacia shrubland. As is typical of most species within the genus, nests are in soil. The syntype worker examined lacks a head and is in generally poor condition, but its identity is not in doubt.

Figures

FIGURE 12. Iridomyrmex angusticeps (Bushy Island, Great Barrier Reef, Qld, ANIC32-042168): A. Front of head; B. Side of body; C. Top of body; D. Distribution of material examined.