Polyrhachis setosa

Nothing is known about the biology of Polyrhachis setosa.

Identification
In many aspects Polyrhachis setosa is similar to Polyrhachis decumbens, from Australia. They differ in the form of their pubescence which in Polyrhachis setosa is mostly erect and bristle-like, while it is shorter and mostly decumbent in Polyrhachis decumbens. Additionally, in Polyrhachis setosa the eyes in full face view do not or only just reach the lateral cephalic outline, while in Polyrhachis decumbens they clearly break the outline of the head. (Kohout 2006)

Distribution
Known only from the type locality in the Solomon Islands.

This taxon was described from Solomon Is.

Abundance
Only known from type material.

Castes
The males of Polyrhachis setosa are unknown.

Worker
Dimensions (holotype cited first): TL c. 4.89, 4.89-5.09; HL 1.28, 1.28-1.34; HW 1.25, 1.25-1.31; CI 98, 98; SL 1.50, 1.43-1.56; SI 120, 114-120; PW 0.94, 0.94-0.97; MTL 1.78, 1.72-1.84 (4 measured).

Apical mandibular tooth long, other teeth shorter and subequal. Anterior clypeal margin with central flange irregularly serrated. Clypeus in profile straight anteriorly, posteriorly rounding into well impressed basal margin. Frontal triangle indistinct. Frontal carinae sinuate with very weakly raised margins; central area rather flat with short, weakly indicated frontal furrow. Sides of head in front of eyes convex, rather strongly converging towards mandibular bases; behind eyes sides widely rounding into convex occipital margin. Eyes weakly convex, in full face view not, or just, reaching lateral cephalic outline. Ocelli lacking. Pronotum in dorsal view with humeri narrowly rounded or very weakly angular in some specimens; greatest width of pronotum across or just behind shoulders. Mesosoma in profile with moderately convex pronotum; promesonotal suture rather distinct; mesonotal dorsum weakly convex; metanotal groove indicated by shallow depression in outline; propodeal dorsum flat with pair of rather indistinct spines or tuberculae; propodeal declivity virtually vertical. Petiole with anterior face straight, posterior face convex; dorsum armed with four short spines of subequal length; dorsal pair broad-based, more tooth-like; lateral pair distinctly more slender. Subpetiolar process almost as wide as long with anterior angle acute, narrowly rounded posteriorly. Anterior face of first gastral segment very weakly concave at base. Mandibles finely rugose with numerous piliferous pits. Head, mesosoma and gaster shagreened with numerous punctures; sculpturation somewhat more intense laterally with meso- and metapleurae distinctly reticulate-rugose.

Mandibles with numerous, short, mostly decumbent hairs at mandibular bases; longer, semierect hairs arising near masticatory borders. Virtually all body surfaces, including antennal scapes and legs, with numerous erect, bristle-like hairs and rather short, decumbent hairs arising from abundant punctures and pits.

Colour. Black; mandibles, condylae, distal half of apical funicular segments and trochanters light to medium reddish-brown. Antennal scapes dark brown, progressively lighter towards apex, including funiculi. Legs generally medium to dark reddish-brown; tarsi black. Gaster ventrally very dark reddish-brown.

Queen
Dimensions: TL c. 5.90; HL 1.40; HW 1.28; CI 91; SL 1.68; SI 131; PW 1.34; MTL 2.09 (1 measured). Apart from sexual characters, similar to worker except: pronotal humeri rounded; mesoscutum almost as long as wide with lateral margins converging anteriorly, forming evenly rounded anterior margin; median line weakly indicated; parapsides flat anteriorly, weakly raised posteriorly; mesoscutum in profile with rounded anterior face and very weakly convex dorsum. Mesoscutellum distinctly more convex, moderately raised above dorsal plane of mesosoma; metanotal groove distinct. Propodeum with pair of distinct teeth; dorsum convex in outline, medially rounding into virtually vertical declivity in uninterrupted curve. Petiole relatively narrow, parallel-sided in dorsal view, armed with four, subequal teeth. Other characters virtually identical to those of worker.

Male
Unknown.

Type Material
Holotype worker and paratype queen in ; 1 paratype worker each in, and.

Type Locality Information
HOLOTYPE: SOLOMON IS, GUADALCANAL, Mt Austen, 09°29’S, 159°59’E, 13.x.1965, P.J.M. Greenslade acc. 29691 (worker). PARATYPES: data as for holotype (4 workers); ditto, Mt Austen Rd, 11.ii.1965, P.J.M. Greenslade acc. 15721 (dealate queen).