Polyrhachis sinuata

The unique holotype of this species was collected foraging on low vegetation in open woodland along a walking track and, in spite of a subsequent search, no other specimens were found. Polyrhachis sinuata appears to be a rare species endemic to higher elevations along the summit of Lelet Plateau on New Ireland, Papua New Guinea.

Identification
A member of the Polyrhachis continua species group in the subgenus Myrma

Kohout (2013) - Polyrhachis sinuata is a very distinct species featuring very short and slender pronotal spines and a finely, somewhat longitudinally, reticulate-striate mesosomal dorsum. Also, the shape of the eyes differs from other species of the continua-group in being flat with posterior blinkers, quite similar to those in species of subgenus Hemioptica Roger (see Dorow and Kohout 1995) or P. aculeata-group species of the subgenus Myrma.

Distribution
New Ireland Island (Bismark Archipelago)

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

Castes
Sexuals and immature stages unknown.

Nomenclature

 *  sinuata. Polyrhachis sinuata Kohout, 2013: 24, figs. 9, 13-14 (w.) PAPUA NEW GUINEA.

Worker
Dimensions: TL c. 10.84; HL 2.65; HW 2.09; CI 79; SL 3.63; SI 174; PW 1.53; MTL 3.73.

Anterior clypeal margin arcuate. Clypeus without distinct median carina; virtually straight in profile with shallow basal margin. Frontal triangle distinct. Frontal carinae sinuate with only moderately raised margins anteriorly, flat posteriorly; central area flat with indistinct frontal furrow. Sides of head in front of eyes straight towards mandibular bases; behind eyes sides produced into blunt carina extending towards occipital corners. Eyes rather flat, notably when viewed from above, with posterior blinkers, in full face view eyes marginally exceeding lateral cephalic outline. Ocelli lacking; position of median ocellus indicated by distinct pit in cephalic sculpturation. Pronotum armed with very short, slender, anterolaterally and dorsally directed spines with lateral edges continuous with pronotal margins in convex line towards promesonotal suture. Dorsum of mesosoma convex, only marginally wider than long; lateral margins only narrowly and weakly raised anteriorly, converging posteriorly into distinct metanotal groove. Propodeal dorsum in profile forming single convex line with declivity; lateral margins only weakly converging posteriorly in dorsal view, terminating in weakly raised, blunt tuberculae. Petiole, including spines, as wide as high; dorsal spines relatively short and slender; lateral teeth short. Anterior face of first gastral segment flat, marginally higher than full height of petiole.

Mandibles distinctly, longitudinally striate with numerous piliferous pits towards masticatory borders. Clypeus reticulate-punctate with rest of head and sides mostly longitudinally striate. Dorsum of mesosoma finely, more-or-less regularly, longitudinally striate; sides of mesosoma reticulate-punctate with sculpture organised into somewhat irregular striations. Petiole very finely reticulate-punctate. Gaster reticulate-punctate with sculpture on dorsum somewhat longitudinally striate.

Colour. Black; mandibular teeth dark reddish brown, narrow reddish band along masticatory border. Apical funicular segments and legs very dark reddish brown; tarsi mostly black. Gaster black, apex and venter dark reddish brown.

Etymology
Named for the somewhat sinuate outline of the mesosoma in dorsal view.

References based on Global Ant Biodiversity Informatics

 * Kohout R. J. 2013. A review of the Polyrhachis continua species-group of the subgenus Myrma Billberg (Hymenoptera: Formicidae: Formicinae) with keys and descriptions of new species. Australian Entomologist 40(1): 13-46.