Iridomyrmex bigi Shattuck
Creators: name: Heterick, Brian E.
name: Shattuck, Steve
Publisher: name: Zenodo
Year: 2011
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Hymenoptera
Formicidae
Iridomyrmex
Iridomyrmex bigi

description: <i>Iridomyrmex bigi</i> Shattuck (Fig. 17) <i>Iridomyrmex bigi</i> Shattuck, 1993a: 119, fig. 9. <i>Iridomyrmex variscapus</i> Shattuck, 1993a: 141, fig. 9. <b>New synonym.</b> <b>Types:</b> <i>Iridomyrmex bigi</i> Shattuck: Holotype worker from Henbury Crater, 24°35'S 133°09'E, Northern Territory (ANIC, ANIC32-007345, examined). Paratypes: same data as holotype (ANIC, ANIC32-007346, 19 workers, examined; ANIC, ANIC32-015003, 11 workers, examined; ANIC, ANIC32-015014, 12 workers, examined; BMNH, 3 workers; MCZC, 3 workers). <i>Iridomyrmex variscapus</i> Shattuck: Holotype worker from Sandringham, Queensland (ANIC, ANIC32-009175, examined). Paratypes: same data as holotype (ANIC, ANIC32-009176, 7 workers, examined; BMNH, 2 workers; MCZC, 2 workers). <b>Worker Description. <i>Head.</i></b> 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). Number of ocelli two; in full-face view, eyes set above midpoint of head capsule; in profile, eye set anteriad of head capsule; eye elongate. Frontal carinae convex; antennal scape surpassing posterior margin of head by 1–2 x its diameter. Erect setae on scape present on outside of antennal scape only; prominence on anteromedial clypeal margin projecting as triangular spur; mandible regularly triangular with oblique basal margin; long, curved setae on venter of head capsule absent. <i>Mesosoma.</i> 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 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. Erect propodeal setae numerous (12 or more), short and bristly. <i>Petiole.</i> Dorsum of node acuminate; node thin, scale-like, orientation more-or-less vertical. <i>Gaster.</i> Non-marginal erect setae of gaster present on first gastral tergite; marginal erect setae of gaster present on first tergite. <i>General characters.</i> Allometric differences between workers of same nest absent. Colour foreparts light brick-red to dark crimson, gaster brown with weak bluish to purplish iridescence in light-coloured specimens. Colour of erect setae light brown. <b>Measurements.</b> <i>Worker</i> (n = 16) <i>—</i> CI 94–105; EI 30–37; EL 0.54–0.62; EW 0.28–0.36; HL 1.60–1.91; HW 1.50–1.96; ML 0.82–1.03; PpH 0.23–0.29; PpL 0.85–0.98; SI 78–97; SL 1.38–1.61. <b>Comments.</b> <i>Iridomyrmex bigi</i> is a very odd-looking <i>Iridomyrmex</i>: the combination of the very large eye, pointed node and the general confinement of the erect setae to the anterior margin of the antennal scape make it impossible to confuse this with any other ant in the genus. However, clypeal and mesosomal characters and preliminary molecular data place this ant close to the meat ants (<i>I. purpureus</i> species-complex), albeit as a sister to this complex. Shattuck (1993b) separated the form <i>I</i>. <i>variscapus</i> from <i>I</i>. <i>bigi</i> on the basis of the paler ground colour of the head and mesosoma and the colour of the scape in workers. However, when the workers from these two taxa used in the revision of the <i>I</i>. <i>purpureus</i> group were revisited in the current project, the variability in colour was found to be in conformity with intraspecific variation seen in other <i>Iridomyrmex</i> species. The centre of the antennal scape is much lighter than its edges in both taxa, and the flagellum is generally paler than the scape. The workers of <i>I</i>. <i>variscapus</i>, all of which come from a single nest in Sandringham, Queensland, share the same structural and setae patterns as <i>I</i>. <i>bigi</i>, and the morphometric measurements and indices used by Shattuck all overlap with those of <i>I</i>. <i>bigi</i>. <i>Iridomyrmex variscapus</i> therefore becomes a junior synonym of <i>I. bigi</i> in this monograph. This appears to be a rare species, and apart from one worker (without collection data) supplied by A. Andersen, no additional material has come to light since Shattuck’s (1993b) revision.
description: Published as part of <i>Heterick, Brian E. &amp; Shattuck, Steve, 2011, Revision of the ant genus Iridomyrmex (Hymenoptera: Formicidae) 2845, pp. 1-174 in Zootaxa 2845 (1)</i> on pages 51-52, DOI: 10.11646/zootaxa.2845.1.1, http://zenodo.org/record/5287811
description: {"references": ["Shattuck, S. O. (1993 a) Revision of the Iridomyrmex purpureus species-group (Hymenoptera: Formicidae). Invertebrate Taxonomy, 7, 113 - 149.", "Shattuck, S. O. (1993 b) Revision of the Iridomyrmex calvus species-group (Hymenoptera: Formicidae). Invertebrate Taxonomy, 7, 1303 - 1325."]}