Polyrhachis tuberosa

According to the data label, specimens of the type series were collected "ex nest upon pawpaw leaves in association with Amblypelta lutescens papuensis Brown". (Kohout 2006)

Identification
Polyrhachis tuberosa belongs to a group of species of rather similar appearance that are collectively identified as Polyrhachis rastellata (sensu lato), with their taxonomy presently under review. However, Polyrhachis tuberosa can be easily separated from Polyrhachis rastellata by its high, strongly convex mesosoma with the anterior face of the pronotum ascending towards its summit in an almost straight line. In contrast the outline of the mesosoma in Polyrhachis rastellata is lower and more uniformly rounded with the anterior face of the pronotal dorsum distinctly convex. Also, the pronotal humeri in Polyrhachis tuberosa are widely rounded, while in Polyrhachis rastellata the humeri are subangular with the greatest width of the pronotal dorsum across, or just behind the shoulders. The legs in Polyrhachis tuberosa are quite dark reddish-brown, or almost black, while in Polyrhachis rastellata the legs are very light red or orange. (Kohout 2006)

Distribution
Known only from the type locality (see below).

Distribution based on Regional Taxon Lists
Indo-Australian Region: New Guinea.

Abundance
Known only from types.

Castes
Known only from workers.

Nomenclature

 *  tuberosa. Polyrhachis tuberosa Kohout, 2006b: 133, figs. 11G-H (w.) NEW GUINEA.

Worker
Dimensions (holotype cited first): TL c. 6.25, 5.80-6.70; HL 1.62, 1.56-1.72; HW 1.56, 1.50-1.72; CI 96, 96-98; SL 1.90, 1.84-2.00; SI 122, 117-123; PW 1.15, 1.12-1.28; MTL 2.25, 2.15-2.34 (9 measured).

Clypeus in profile weakly convex, narrowly rounding posteriorly into rather shallow basal margin. Frontal triangle indistinct. Frontal carinae sinuate with raised margins; central area medially concave with distinct frontal furrow. Sides of head in front of eyes weakly convex, converging towards mandibular bases; behind eyes sides rounding into convex occipital margin. Eyes convex, in full face view clearly breaking lateral cephalic outline. Ocelli lacking. Pronotum in dorsal view with humeri widely rounded; greatest pronotal width at mid-length of segment. Mesosoma in profile with pronotum relatively high, ascending towards rather short summit in very weakly curved line; promesonotal suture distinct, flat in profile; mesonotal dorsum weakly convex; metanotal groove very faintly indicated; propodeal dorsum descending into rather low, oblique declivity in widely open curve. Petiole with anterior face very weakly convex, almost flat; posterior face distinctly convex; dorsum armed with four, rather short, subequal teeth. Subpetiolar process acute anteriorly, bluntly angular posteriorly. Anterior face of first gastral segment marginally higher than petiole, evenly rounding onto dorsum of segment.

Mandibles very finely, irregularly rugose with shallow piliferous pits. Head, mesosoma and gaster shagreened; intensity of sculpturation increasing laterally, becoming weakly reticulate-rugose on sides of pronotum and mesosoma with meso- and metapleaurae more distinctly sculptured. Petiole finely reticulate dorsally, lower portions more heavily sculptured. Numerous, rather shallow punctures and piliferous pits over most body surfaces.

Mandibles with numerous semierect and curved hairs on masticatory borders. Anterior clypeal margin with usually 2, relatively long, anteriorly directed setae medially and fringe of shorter setae laterally. A few pairs of medium length, erect hairs near anterior and basal clypeal margins and along frontal carinae; single pair of slightly longer hairs on vertex. Summit of mesonotal dorsum with tuft of a few, relatively long, variously curved hairs. Gaster with numerous, erect, somewhat posteriorly directed hairs lining posterior margins of segments, hairs more abundant on ventral surfaces.

Colour. Black; mandibular masticatory borders, condylae and tips of apical funicular segments light reddish- or yellowish-brown. Legs medium to very dark reddish-brown, almost black in some specimens, with distal ends of trochanters and most of tibiae a shade lighter; tarsi and proximal ends of tibiae narrowly black. Gastral segments in most specimens with posterior margins somewhat diffusely reddish-brown.

Type Material
HOLOTYPE: PAPUA NEW GUINEA, Milne Bay Prov., Puni Puni Point, 10°12’S, 150°27’E, 24.ix.1960, A. Catley (worker). PARATYPES: data as for holotype (8 workers). Holotype and 2 paratypes in ; 2 paratypes in ; 1 paratype each in, , and.

References based on Global Ant Biodiversity Informatics

 * Janda M., G. D. Alpert, M. L. Borowiec, E. P. Economo, P. Klimes, E. Sarnat, and S. O. Shattuck. 2011. Cheklist of ants described and recorded from New Guinea and associated islands. Available on http://www.newguineants.org/. Accessed on 24th Feb. 2011.
 * Kohout R.J. 2006. Review of Polyrhachis (Cyrtomyrma) Forel of Australia, Borneo, New Guinea and the Solomon Islands with descriptions of new species. Memoirs of the Queensland Museum 52: 87-146.