Polyrhachis hybosa

Polyrhachis hybosa has been collected foraging on low vegetation.

Identification
Polyrhachis hybosa is very similar to Polyrhachis dorsena 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. (Kohout 2006)

Distribution
Known only from the Northern Province of Papua New Guinea.

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

Castes
Known only from workers.

Nomenclature

 *  hybosa. Polyrhachis hybosa Kohout, 2006b: 126, figs. 9C-D (w.) NEW GUINEA.

Worker
Dimensions (holotype cited first): TL c. 7.11, 6.85-7.11; HL 1.81, 1.72-1.81; HW 1.75, 1.65-1.78; CI 97, 96-98; SL 2.34, 2.28-2.34; SI 134, 131-138; PW 1.37, 1.31-1.40; MTL 2.90, 2.81-2.90 (3 measured).

Clypeus in profile virtually straight, rounding posteriorly into very shallow basal margin. Frontal triangle weakly impressed, rather indistinct. Frontal carinae sinuate with raised margins; central area medially concave with relatively short, weakly impressed frontal furrow. Sides of head in front of eyes convex, converging towards mandibular bases; behind eyes sides widely rounding into broadly convex occipital margin. Eyes weakly convex, almost flat, situated well inwards from occipital corners; not reaching lateral cephalic outline in full face view. Ocelli lacking. Pronotum in dorsal view widely rounded; greatest pronotal width at mid-length of segment. Mesosoma in profile with pronotum strongly convex, distinctly swollen, anterior face rising steeply towards summit; promesonotal suture distinct, rather flat in profile; mesonotal dorsum weakly convex, gently descending posteriorly; metanotal groove faintly indicated; outline of propodeal dorsum flat, rounding into steep declivity in uninterrupted curve. Petiole in profile virtually triangular, with anterior and posterior faces straight; dorsum armed with four short, subequal teeth; dorsal pair distinctly closer to each other than to lateral spines, tips slightly bent backwards. Subpetiolar process acute anteriorly, rounded posteriorly. Anterior face of first gastral segment straight with anterodorsal margin lower than full height of petiole.

Mandibles finely, longitudinally rugose with numerous piliferous pits. Head, mesosoma and gaster finely shagreened, sculpturation marginally coarser on lower parts of mesosoma; meso- and metapleurae weakly reticulate-rugose. Dorsal half of petiole finely, transversely reticulate, sulpturation distinctly coarser around base. Numerous shallow punctures and piliferous pits scattered over all body surfaces. Mandibles with several rather short, semierect hairs on masticatory borders. Anterior clypeal margin with a few medium length, anteriorly directed setae medially and a few short setae laterally. A few pairs of medium length hairs near anterior and basal clypeal margins and along frontal carinae; single pair of erect hairs on vertex. A few longer, semierect hairs on posterior faces of fore coxae and along posterior margins of apical gastral segments, more abundant ventrally. Whole body with very short, appressed hairs arising from numerous pits.

Colour. Black; mandibular teeth, condylae and tips of apical funicular segments reddish-brown. Legs medium to dark reddish-brown with proximal ends of tibiae and tarsi black. Posterior margins of gastral segments somewhat diffusely reddish-brown.

Type Material
HOLOTYPE: PAPUA NEW GUINEA, Northern Prov., Kokoda, 1200ft, iv.1933 (L.E. Cheesman #350, B.M. 1933-577) (w) PARATYPES: data as for holotype (2 workers). Holotype in, 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.