Polyrhachis tenebra

The unique holotype of P. tenebra was collected foraging on the ground in savannah woodland. Like most other Hagiomyrma species inhabiting this kind of habitat, it is most likely a ground-nesting species.

Identification
A member of the penelope species-group in the Polyrhachis subgenus Hagiomyrma. Polyrhachis tenebra is somewhat similar to Polyrhachis tanami with their differences discussed in remarks section of the latter species.

Distribution based on Regional Taxon Lists
Australasian Region: Australia.

Castes
Known only from the worker caste.

Nomenclature

 *  tenebra. Polyrhachis (Hagiomyrma) tenebra Kohout, 2013: 550, figs. 9G-H (w.) AUSTRALIA.

Worker
TL c. 6.35; HL 1.62; HW 1.31; CI 81; SL 1.75; SI 133; PW 1.12; MW 0.65; PMI 172; MTL 2.00.

Anterior clypeal margin with shallow, acutely denticulate, median flange. Clypeus with median carina; almost straight in profile, weakly elevated posteriorly; basal margin very shallowly impressed. Frontal carinae sinuate, with narrowly raised margins. Sides of head in front of eyes converging towards mandibular bases in weakly convex line; behind eyes, sides rounding into convex occipital margin. Eyes convex, in full face view marginally exceeding lateral cephalic outline. Ocelli lacking. Pronotal humeri rounded with narrowly raised anterior margins; promesonotal suture distinct. Mesonotum with margins converging towards poorly indicated metanotal groove. Propodeal dorsum armed with slender, horizontal, divergent spines, with tips weakly curved outwards. Petiolar spines widely divergent, obliquely elevated from bases and continued horizontaly towards weakly upturned tips. Anterior face of first gastral tergite widely rounding onto dorsum.

Mandibles finely, longitudinaly striate with piliferous pits. Head, mesosoma and petiole reticulate-punctate with sculpturation relatively fine and uniform. Spines sculptured at bases, smooth and polished towards tips. Gaster shagreened.

Mandibular masticatory and outer borders with numerous, curved, golden hairs; hairs shorter and suberect towards bases. Anterior clypeal margin with a few longer setae medially and fringe of shorter setae laterally. Most body surfaces, including appendages, with numerous, rather short, golden hairs; marginally longer and variously directed hairs on dorsum of mesosoma. Gaster with posteriorly directed hairs on dorsum; somewhat longer hairs on apical segments and venter. Mostly silvery, closely appressed pubescence on head, mesosoma and petiole; pubescence distinct, somewhat longer and pale golden on anterior portion of pronotal dorsum, including humeri. Gastral dorsum with rather abundant, golden pubescence, almost hiding underlying sculpturation; much diluted, silvery pubescence on gastral venter.

Black; mandibles reddish-brown.

Etymology
Derived from the Latin tenebrosus, meaning dark, darkness, in reference to its virtually black appearance.

References based on Global Ant Biodiversity Informatics

 * Kohout R.J. 2013. Revision of Polyrhachis (Hagiomyrma) Wheeler, 1911 (Insecta: Hymenoptera: Formicidae: Formicinae). Memoirs of the Queensland Museum  Nature 56: 487577