Polyrhachis dorsena

The type colony was collected from a silk nest built on the underside of a palm leaf in rainforest. (Kohout 2006)

Identification
Polyrhachis dorsena is similar to Polyrhachis hybosa with both species featuring a distinctly swollen pronotal dorsum and widely rounded pronotal shoulders. However, the mesosoma in Polyrhachis hybosa is distinctly more robust in comparison with that of Polyrhachis dorsena. Also, the eyes in Polyrhachis hybosa are rather flat and they do not reach the lateral cephalic outline in full face view. The eyes in Polyrhachis dorsena are moderately convex and with the head in full face view, they marginally exceed the lateral outline. Polyrhachis dorsena also resembles Polyrhachis conspicua, however, Polyrhachis dorsena has the pronotal dorsum less strongly convex and lacks a medial, longitudinal furrow along its summit. (Kohout 2006)

Distribution
New Guinea

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

Castes
Males have not been collected. Immature stages (larvae and pupa) in collection. (Kohout 2006)

Nomenclature

 *  dorsena. Polyrhachis dorsena Kohout, 2006b: 124, figs. 8G-H (w.q.) NEW GUINEA.

Worker
Dimensions (holotype cited first): TL c. 6.35, 5.80-6.35; HL 1.65, 1.50-1.65; HW 1.62, 1.40-1.62; CI 98, 93-98; SL 2.06, 1.78-2.06; SI 127, 124-131; PW 1.25, 1.12-1.25; MTL 2.40, 2.15-2.40 (6 measured).

Clypeus in profile very weakly convex, narrowly rounding posteriorly into weakly medially impressed basal margin. Frontal triangle very weakly impressed, indistinct. Frontal carinae sinuate with very weakly raised margins; central area rather flat with weak frontal furrow. Sides of head in front of eyes weakly convex, converging towards mandibular bases; behind eyes sides rounding into convex occipital margin. Eyes weakly convex, in full face view not reaching lateral cephalic outline. Ocelli lacking, relative position of median ocellus indicated by shallow puncture in sculpture. Pronotum in dorsal view with humeri widely rounded; greatest width of pronotal dorsum at mid-length of segment. Mesosoma in profile with pronotum strongly convex, its anterior face rising steeply, vertically in some specimens; promesonotal suture distinct; mesonotal dorsum almost flat, gently descending posteriorly; metanotal groove weakly indicated; propodeal dorsum and declivity forming single, uninterrupted curve in profile. Petiole with anterior face straight, posterior face convex; dorsum armed with four subequal spines; dorsal pair closer to each other than to lateral spines, tips slightly bent backwards. Subpetiolar process acute anteriorly, bluntly angular posteriorly. Anterior face of first gastral segment marginally lower than apices of dorsal petiolar spines.

Mandibles very finely longitudinally rugose with numerous piliferous pits towards bases. Head, mesosoma and gaster rather polished, finely shagreened with sculpturation distinctly more reticulate-rugose laterally, notably on meso- and metapleurae. Petiole with anterior face finely, mostly transversely reticulate with sculpture on posterior face distinctly finer and more polished; lower portions of petiole distinctly reticulate-rugose. All dorsal body surfaces with numerous piliferous pits and shallow punctures.

Mandibles with a few short, semierect hairs along masticatory borders. Anterior clypeal margin with a few anteriorly directed setae medially and several shorter setae laterally. A few pairs of erect hairs near anterior and basal clypeal margins and along frontal carinae. Tuft of medium length, somewhat curved hairs on summit of mesonotum, some almost as long as greatest diameter of eye. A few rather isolated hairs on anterior faces of fore coxae and ventral surfaces of fore femora. Numerous erect hairs along posterior margins of gastral segments, more abundant ventrally. Very short, appressed hairs arising from pits and shallow punctures over most body surfaces.

Colour. Black; mandibular masticatory borders, condylae, tips of apical funicular segments and joints between trochanters and femorae, reddish-brown. Antennae and legs medium reddish-brown; tarsi black. Anterior and ventral portions of gaster rather diffusely blotched with reddish-brown.

Queen
Dimensions: TL c. 8.06; HL 1.84; HW 1.68; CI 91; SL 2.15; SI 128; PW 1.84; MTL 2.72 (1 measured). Apart from sexual characters, very similar to worker except: pronotal humeri widely rounded, mesoscutum slightly transverse, with evenly rounded anterior margin; median line short; parapsides rather flat, slightly elevated posteriorly; mesoscutum in profile distinctly convex anteriorly, with flat dorsum. Mesoscutellum convex, well elevated above dorsal plane of mesosoma. Metanotal groove distinct. Propodeal dorsum weakly convex, widely rounding into oblique declivity. Other characters, including sculpturation and pubescence as in worker.

Type Material
HOLOTYPE: PAPUA NEW GUINEA, West Sepik Prov., Torricelli Mtns, 1-2km NE of Lumi, 03°28’S, 142°02E, 400-500m, 4-13.viii.1984, R.J. Kohout acc. 84.232 (worker). PARATYPES: data as for holotype (19 workers, 7 alate queens). Holotype, most paratype workers and paratype queen in ; 3 paratype workers and 1 paratype queen in, and ; 1 paratype worker 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.