Polyrhachis aberrans

Specimens have been collected in fogging samples from 230-400 m.

Identification
A member of the Polyrhachis armata species group.

Kohout (2008) - Direct comparison of P. aberrans workers with the unique holotype queen of Polyrhachis peregrina Fr. Smith (OXUM) has shown them to be superficially very similar. Both species have the characteristic appressed, pale golden pubescence, which is particularly distinct on the sides of the mesosoma and the propodeal dorsum, petiole, gaster and spines (except their extreme tips). However, they distinctly differ in a number of characters on the head. The frontal carinae in P. aberrans are only moderately elevated, with the central area relatively wide and shallowly concave. In contrast the frontal carinae in P. peregrina are prominent and markedly closer together, creating a very narrow and deeply excavated central area. The eyes in P. aberrans are moderately convex, clearly breaking the lateral outline of the head in full frontal view, while in P. peregrina the eyes are weakly convex, barely breaking the lateral cephalic outline. The clypeus in P. aberrans features a distinct, posteriorly raised, median carina that terminates just short of the deeply impressed basal margin. In P. peregrina the median clypeal carina is feebly indicated posteriorly and, in profile, the basal clypeal margin is only shallowly impressed. In addition, the pronotal spines in P. aberrans are moderately divergent and longer than their basal widths, while in P. peregrina they are short, only slightly longer than their basal widths and strongly turned outwards and curved downwards. The shape of the petiole is almost identical in both species, featuring a narrow dorsal margin and posteriorly divergent, almost arrow-shaped spines. The propodeal spines are relatively long and somewhat downturned in P. aberrans, but distinctly shorter and straight in P. peregrina. In both species the dorsum of the petiole bears two short, acute, posteriorly directed intercalary spines that are much closer together in P. aberrans. Both species are black, but P. aberrans has the extreme tips of the apical antennal segments and the tibiae, except their proximal ends, light reddish-brown.

Distribution based on Regional Taxon Lists
Indo-Australian Region: Indonesia, Sulawesi.

Castes
Known only from the worker caste.

Nomenclature

 *  aberrans. Polyrhachis aberrans Kohout, 2008a: 292, figs. 8A-B (w.) INDONESIA (Sulawesi).

Worker
(holotype cited first): TL c. 7.46, 6.60-8.06; HL 1.68, 1.56-1.89; HW 1.34, 1.27-1.47; CI 80, 78-81; SL 2.28, 2.09-2.50; SI 170, 164-173; PW 1.25, 1.18-1.43; MTL 2.37, 2.18-2.62 (10 measured).

Anterior clypeal margin with medially notched, truncate flange, flanked laterally by acute angles. Clypeus with distinct, posteriorly raised median carina, terminating just short of basal margin; in profile clypeus straight with basal margin well impressed, laterally basal margin indicated by obscure, thin line. Frontal triangle indistinct. Frontal carinae sinuate with moderately raised margins; central area relatively wide and shallowly concave with frontal furrow weakly indicated. Sides of head in front of eyes converging anteriorly in virtually straight line; behind eyes sides rounding into convex occipital margin. Eyes convex, in full face view clearly breaking lateral cephalic outline. Ocelli lacking. Pronotum armed with pair of anterolaterally and weakly downward-directed acute spines. Propodeum with pair of strong, horizontal, posteriorly directed, acute spines. Petiole with anterior face straight, abruptly rounding onto dorsum; posterior face strongly convex; dorsum armed with a pair of lateral, widely diverging, horizontal spines; bases of spines clearly situated below summit of dorsum; apices of spines strongly curved downwards and weakly outwards; dorsum of petiole also with pair of slender, acute, horizontally and posteriorly directed intercalary spines with their tips curved downwards. Subpetiolar process acute anteriorly, widely rounding posteriorly. Anterior face of first gastral segment distinctly lower than height of petiole, widely rounding onto dorsum.

Mandibles finely reticulate-rugose with numerous piliferous pits. Head, mesosoma, petiole and gaster shagreened with summit of pronotum and mesonotum distinctly coarsely punctate. Sculpturation increasing in intensity laterally with sides of mesosoma and petiole reticulate-punctate. Apices of spines rather smooth and polished.

Mandibular masticastory borders with only a few, curved hairs and numerous very short appressed hairs arising from pits. Anterior clypeal margin with 3 long, anteriorly directed setae and several short setae fringing margin laterally. A few pairs of hairs near anterior and basal clypeal margins, along frontal carinae and a single pair on vertex. A very few erect hairs on fore coxae and single hair arising from ventral surface of each trochanter and femur. Gaster with medium length, golden, erect hairs lining posterior margins of apical gastral segments with hairs more abundant dorsally. Body with relatively long, mostly appressed, pale golden, pubescence; most abundant on head and dorsum of mesosoma, but rather diluted on vertex, midline and posterior half of mesonotal dorsum. Pubescence almost completely absent from summit of pronotal dorsum and tips of spines. Gastral dorsum with pubescence shorter, more closely appressed and dense, almost completely hiding underlying sculpturation.

Colour. Black; mandibles black with narrow band across masticatory borders and apical teeth reddish-brown. Funiculi with distal segments progressively lighter and tip of apical segment yellowish-brown. Tibiae light reddish-brown, except proximal ends narrowly black.

Type Material
HOLOTYPE: SULAWESI UTARA: Dumoga-Bone NP, 400m, 11.ii.1985, fog., N.E. Stork et al. (worker). PARATYPES: data as for holotype (5 workers); ditto, 230m, 11.vi.1985, fog., N.E. Stork et al. (2 workers); ditto, 230m, 30.ix.1985, fog., N.E. Stork et al. (2 workers); ditto, Subcamp Barney’s, 300m, x.1985 (Bosmans & Van Stalle #022) (w). Holotype and (5) paratypes in, 2 paratypes each in , and , 1 paratype in.

References based on Global Ant Biodiversity Informatics

 * Kohout, R. J. 2008. A review of the Polyrhachis ants of Sulawesi with keys and descriptions of new species (Hymenoptera: Formicidae: Formicinae). Memoirs of the Queensland Museum 52:255-317.