Polyrhachis abdita

Presently known from the Lelet Plateau on the island of New Ireland.

Identification
Kohout (2007) - P. abdita is very similar to Polyrhachis dohrni, but can be distinquished by the characters listed under the latter. Of these, the most important are the more flattened eyes and complete absence of an anterodorsal process on the first gastral segment in abdita. Because of their similarity and adjoining distributions, abdita could be considered a higher altitude population of dohrni. However, with most of the distinguishing characters constant and no intermediate forms detected, I believe they represent distinct species.

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

Castes
Known only from the worker caste.

Nomenclature

 *  abdita. Polyrhachis (Aulacomyrma) abdita Kohout, 2007a: 195, figs. 1, 4, 7 (w.) NEW GUINEA.

Worker
TL c. 4.64-5.44 (5.19); HL 1.15-1.37 (1.31); HW 1.03-1.22 (1.18); CI 88-90 (90); SL 1.22-1.40 (1.40); SI 114-119 (119); PW 1.00-1.18 (1.18); MTL 1.28, 1.09-1.34 (1.28) (13 measured). Anterior clypeal margin arcuate with shallow emargination medially; in profile clypeus virtually straight with very weakly impressed basal margin, indicated laterally by a faint line that barely breaks cephalic sculpture. Frontal carinae sinuate, with laminate lobes. Sides of head very weakly convex, almost straight in front of eyes before converging towards bases of mandibles. Eyes rather flat, with anterior margins somewhat sunk into shallow depressions in cephalic sculpture; in full face view almost level with, but failing to break lateral cephalic outline. Mesosoma marginate along entire length. Pronotal humeri armed with broad-based, angulate, acute teeth, that are laterally continuous with pronotal margin. Dorsum of pronotum widest at midlength. Promesonotal suture distinct; metanotal groove lacking dorsally, position marked by shallow emarginations in lateral margin. Propodeum with lateral margins only narrowly rounded posteriorly; dorsum descending into virtually vertical declivity in an unobstructed curve. Petiole with sharp dorsal margin, its apex higher than anterodorsal margin of first gastral segment; lateral petiolar spines directed outwards and slightly curved backwards from bases. First gastral segment concave medially, accomodating posterior face of petiole; anterodorsal margin of concavity rather blunt, not elevated above dorsal face of segment.

Mandibles finely, mostly longitudinally, striate-rugose, with shallow pits towards masticatory border. Sculpture of body consisting of more-or-less regularly spaced striae, that are mostly longitudinal on head, distinctly anteriorly converging on pronotal dorsum and posteriorly converging on mesonotal-propodeal dorsum; striae oblique on sides of mesosoma and longitudinal on sides of gaster. Petiole and dorsum of gaster finely, microscopically, shagreened.

Entire body with numerous semierect to erect, off-white to silvery hairs, that do not exceed greatest diameter of eye in length. Silvery to silvery-grey appressed pubescence fairly abundant, partly concealing underlying sculpture, notably on propodeal dorsum, where it curves towards midline. Gastral pubescence rather abundant, silvery at sides and along posterior margins of segments; becoming distinctly silvery-grey on dorsal surface of first gastral segment.

Black; mandibular masticatory border, apices of antennal scapes, funiculi, femora and tarsi medium to dark reddish brown, with funiculi and tarsi becoming lighter apically. Tibiae distinctly lighter, except their proximal and distal ends, which are very narrowly dark, reddish brown.

Type Material
HOLOTYPE: PAPUA NEW GUINEA, New Ireland Prov., Lelet Plateau, c. 03º20’S, 151º56’E, 800-1000m, 19-24.vii.1984, R. J. Kohout acc. 84.95 (worker). PARATYPES: data as for holotype (12 workers). Type distribution: holotype and 2 paratypes in ; 2 paratypes each in, , , and.

Etymology
Name derived from the Latin word abditus, meaning hidden, concealed.

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. 2007. Revision of the subgenus Aulacomyrma Emery of the genus Polyrhachis F. Smith, with descriptions of new species (pp. 186-253). In Snelling, R.R., Fisher, B.L. & Ward, P.S. (eds). Advances in ant systematics: homage to E.O. Wilson  50 years of contributions. Memoirs of the American Entomological Institute 80: 690 pp.