Polyrhachis manusensis

This species is evidently endemic to Manus Island, Papua New Guinea.

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

Polyrhachis manusensis is characterised by its distinctly striate head and rather broad, longitudinally striate dorsum of mesosoma, which has short, broadly based pronotal spines.

Distribution
Manus Island (Admiralty Islands, Bismark Archipelago)

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

Castes
Sexuals and immature stages unknown.

Nomenclature

 *  manusensis. Polyrhachis manusensis Kohout, 2013: 21, figs. 8, 11-12 (w.) PAPUA NEW GUINEA.

Worker
Dimensions (holotype cited first): TL c. 10.84, 9.68-11.34; HL 2.64, 2.34-2.68; HW 2.00, 1.78-2.06; CI 76, 74-78; SL 3.48, 3.22-3.53; SI 174, 169-181; PW 2.15, 1.87-2.18; MTL 3.58, 3.22-3.73 (14 measured).

Anterior clypeal margin arcuate, medially obtusely truncate. Clypeus with poorly defined, blunt median carina; clypeus virtually straight in profile with rather flat basal margin. Frontal triangle distinct. Frontal carinae sinuate with moderately raised margins; central area with poorly defined frontal furrow. Sides of head in front of eyes weakly concave towards mandibular bases; behind eyes, sides produced into blunt carina extending towards rather prominent occipital corners. Eyes mildly protracted posteriorly; in full face view clearly exceeding lateral cephalic outline. Ocelli lacking. Pronotal dorsum distinctly wider than long with relatively short, broad-based, acute spines directed anterolaterally and curved slightly downwards; lateral edges of spines acute and continuous with weakly upturned pronotal margins. Promesonotal suture distinctly impressed; mesonotal dorsum strongly transverse, with moderately raised lateral margins; metanotal groove deeply impressed laterally, rather flat and posteriorly bowed medially. Propodeal dorsum with lateral margins strongly raised anteriorly, virtually flat posteriorly, terminating in blunt propodeal teeth, lateral borders of teeth continuous posteriorly and somewhat curved inwards into declivity. Petiole scale-like, dorsal margin armed with two, broad-based, acute spines with inner margins forming ‘U’-shaped dorsum of segment; lateral margin of petiole below base of each spine with distinct, acute tooth. Anterior face of first gastral segment flat with anterodorsal margin widely rounding onto dorsum of gaster.

Mandibles distinctly, longitudinally striate with numerous piliferous pits towards masticatory borders. Clypeus reticulate-punctate with rest of head and mesosoma, including sides, distinctly, mostly longitudinally striate; propodeal declivity and petiole, including spines, finely reticulate-punctate. Gaster finely reticulate-punctate with sculpture on dorsum somewhat longitudinally striate.

Mandibular masticatory borders and outer margins with numerous, semierect, golden hairs. Anterior clypeal margin medially with several long, anteriorly directed, golden setae with distinct reddish tint and fringe of shorter setae laterally. Numerous short to medium length, erect to semierect hairs on clypeus, along frontal carinae and vertex, many hairs fringing lateral cephalic outline in full face view. Antennal scapes with several semierect, short to medium length hairs along leading edge and a few hairs along inferior edge towards apices. Mesosoma, except declivity, and legs, except dorsal surfaces of femora, with numerous short to medium length, erect hairs; petiole with numerous shorter hairs along lateral margins near base and a few occasional hairs on dorsal spines. Gaster with numerous medium length, posteriorly inclined hairs, increasing in length towards gastral apex. Closely appressed, silvery white or greyish pubescence variously distributed over most body surfaces, somewhat shorter with distinctly reddish tint on gastral dorsum.

Colour. Black; mandibular teeth and apical funicular segments reddish brown. Legs dark to very dark reddish brown; tarsi mostly black. Gaster black, apex and venter dark reddish brown.

Etymology
Named after Manus Island in the Bismarck Archipelago.

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.