Polyrhachis chaita

Specimens have been collected from fogging samples in natural forest from 400 - 1130 m.

Identification
A member of the Polyrhachis flavicornis species group.

Kohout (2008) - Polyrhachis chaita is somewhat similar to Polyrhachis elii, described from Mantawei I. They both have a distinct cover of whitish-or yellowish-grey, mostly short to medium length, erect hairs. However, P. chaita differs markedly by its distinctly smaller size (HL 1.50-1.59 in P. chaita versus HL 1.84-1.90 in P. elii), bluntly angular humeri and distinctly longer, widely diverging and somewhat curved petiolar spines. In contrast, the pronotal humeri in P. elii are armed with short, but distinct teeth and the petiolar spines are rather short, stubby and only weakly curved inwards. The sculpturation in P. chaita is coarsely rugose and rather irregular, while in P. elii the reticulate-rugose sculpturation is finer and somewhat longitudinally directed, notably on the pronotal dorsum.

Specimens from Lore Lindu NP differ from the type series specimens from Dumoga-Bone in having the petiolar spines more steeply raised, only weakly divergent and curved inwards. Also, the pronotal humeri are distinctly rounded without any indication of humeral angles, while they are bluntly angular in the Dumoga-Bone specimens.

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

Nomenclature

 *  chaita. Polyrhachis chaita Kohout, 2008a: 283, figs. 7A-B (w.q.) INDONESIA (Sulawesi).

Worker
(holotype cited first): TL c. 6.00, 5.74-6.35; HL 1.56, 1.50-1.59; HW 1.22, 1.12-1.25; CI 78, 75-81; SL 1.87, 1.78-1.93; SI 153, 151-159; PW 1.09, 0.90-1.09; MTL 1.72, 1.65-1.72 (14 measured).

Anterior clypeal margin medially with shallow, truncate flange, laterally flanked by acute denticles. Clypeus in profile very weakly convex, rounding posteriorly into moderately impressed basal margin, laterally basal margin partly concealed by coarse sculpturation. Frontal triangle distinct. Frontal carinae sinuate with margins moderately raised; central area concave with poorly indicated frontal furrow. Sides of head in front of eyes straight, anteriorly converging; behind eyes sides rounding into convex occipital margin. Eyes convex, in full face view clearly breaking lateral cephalic outline. Ocelli lacking. Lateral margins of pronotal dorsum widely rounded with humeri bluntly angular; mesonotal dorsum with lateral margins converging posteriorly, weakly raised towards rounded posterior angles. Propodeal dorsum transverse, lateral margins terminating posteriorly in somewhat flattened, dorsally rounded ridges, appearing in profile as acute teeth; inner margins of teeth continued medially only for a short distance, so that propodeal dorsum descends into declivity in medially uninterrupted curve. Petiolar dorsum armed with two, strong, acute spines, arising dorsolaterally from their bases and widely curving at mid length with their tips directed posterodorsally. Anterior face of first gastral segment flat at base, widely rounding onto dorsum.

Mandibles rather smooth, with very weakly, mostly longitudinal striae basally and numerous piliferous pits. Head, mesosoma and gaster very coarsely reticulate-rugose, reticulae on pronotal dorsum somewhat longitudinally oriented. Antennal scapes and petiolar spines with shallow rugae and piliferous pits. Fore coxae finely and shallowly reticulate. Gaster shagreened with numerous piliferous pits.

Very hairy. Mandibular masticatory borders with several curved hairs; outer mandibular margin fringed with numerous, short, erect hairs. Anterior clypeal margin with one long seta medially and few short setae fringing margin laterally. Whole body covered with whitish and/or pale yellow, short to medium length, erect and variously curved hairs; shorter hairs on antennal scapes and dorsal surfaces of femora. Mostly white, decumbent or semierect, scarce pubescence over most dorsal surfaces, dense and more appressed on gaster.

Colour. Black. Mandibles reddish-brown at bases, distinctly lighter towards masticatory borders. Antennal scapes and basal funicular segments dark reddish-brown, with subsequent segments lightening towards apices; condylae, base of antennal scapes and apical funicular segments distinctly light yellow. Coxae black; femora and proximal ends of tibiae very dark reddish-brown with tibiae a shade lighter distally; tarsi light reddish-brown. Gaster dorsally very dark, reddish-brown; sides with somewhat diffuse reddish tint.

Queen
TL c. 7.41; HL 1.72; HW 1.28; CI 74; SL 2.12; SI 166; PW 1.18; MTL 1.68 (1 measured).

Queen very similar to worker, with characters identifying full sexuality, including three ocelli, complete thoracic structure and wings. Pronotal shoulders widely rounded. Mesoscutum only marginally wider than long with lateral margins converging anteriorly, forming moderately rounded anterior margin; median line distinct; parapsides weakly raised posteriorly; anterior face of mesoscutum relatively low in profile; dorsum only weakly convex anteriorly, flat posteriorly. Mesoscutellum only marginally raised above dorsal plane of mesosoma, convex and strongly rounding into distinctly impressed metanotal groove. Propodeal dorsum convex in profile with lateral margins terminating posteriorly in upturned ridges identical to those in worker. Petiolar spines similar to those in worker, slightly shorter. Sculpturation, pilosity and colour scheme virtually as in worker.

Type Material
HOLOTYPE: SULAWESI UTARA: Dumoga-Bone NP, 400m, 11.ii.1985, fog., N.E. Stork et al. (worker). PARATYPES: data as for holotype (13 workers, 1 alate queen). Holotype, 5 paratype workers and paratype queen in ; 2 paratype workers in, , and.

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.