Polyrhachis pacifica

Nothing is known about the biology of Polyrhachis pacifica.

Identification
Polyrhachis pacifica is somewhat similar to Polyrhachis emeryana. They share the highly convex pronotum with the mesonotum and propodeum descending posteriorly in an uneven, stepped outline. They differ in the shape of the pronotal humeri that, in Polyrhachis pacifica are distinctly angular, while they are widely rounded in Polyrhachis emeryana. Polyrhachis undulata is also similar, sharing the unevenly descending mesosomal profile. It differs from Polyrhachis pacifica by a complete lack of propodeal spines and from Polyrhachis emeryana by distinctly angular pronotal humeri. Polyrhachis undulata also differs from both by its larger size (HL 1.53-1.59 in Polyrhachis undulata versus 1.28-1.34 in Polyrhachis pacifica and 1.34-1.40 in Polyrhachis emeryana) and in having the mesonotal dorsum distinctly higher than the pronotum. In Polyrhachis pacifica and Polyrhachis emeryana the summit of the pronotal dorsum is the highest point of mesosoma. (Kohout 2006)

Distribution
Known only from the type localities.

This taxon was described from Solomon Is.

Castes
Known only from workers.

Worker
Dimensions (holotype cited first): TL c. 5.09, 4.94; HL 1.34, 1.28; HW 1.31, 1.28; CI 98, 99; SL 1.50, 1.43; SI 114, 112; PW 1.15, 1.03; MTL 1.72, 1.62 (2 measured).

Clypeus in profile straight, narrowly rounding into impressed basal margin. Frontal triangle indistinct. Frontal carinae sinuate with weakly raised margins; central area rather flat with short frontal furrow. Sides of head in front of eyes weakly convex, converging towards mandibular bases; behind eyes sides rounding into moderately convex occipital margin. Eyes moderately convex, in full face view just reaching lateral cephalic outline. Ocelli lacking. Pronotum in dorsal view widest across distinctly angular humeri. Mesosoma in profile with pronotal dorsum strongly convex; mesosoma posteriorly descending from summit of pronotum in rather uneven outline, weakly impressed at promesonotal suture and distinctly stepped at metanotal groove; propodeal dorsum descending abruptly into steep, very weakly concave declivity; propodeum armed with pair of slender, acute, upturned, dorso-laterally directed spines. Petiole with anterior face straight, posterior face convex; dorsum armed with four acute spines, lateral pair distinctly more slender and almost twice as long as dorsal pair. Anterior face of first gastral segment lower than total height of petiole, base very weakly concave. Mandibles very finely rugose with numerous piliferous pits. Head, mesosoma and gaster shagreened with numerous shallow punctures. Intensity of sculpturation increasing only marginally towards sides of pronotum and lateral portions of mesosoma, with meso- and metapleurae somewhat irregularly reticulate. Petiole with both faces finely transversely wrinkled.

Mandibles near masticatory borders with only a few, semierect, short hairs. Anterior clypeal margin with 3 relatively long, anteriorly directed setae and 4 erect hairs arising just behind anterior margin. A few medium length hairs on extreme apex and ventral surfaces of apical gastral segments. Rest of body virtually hairless, except for numerous microscopic decumbent hairs arising from shallow pits.

Colour. Black; mandibular masticatory borders, condylae, extreme tips of apical funicular segments, distal ends of trochanters, most of tibiae and gastral apex, light to medium reddish-brown. Rest of legs, including tarsi, distinctly darker.

Queen
Unknown

Male
Unknown

Type Material
Holotype in ; paratype in.

Type Locality Information
HOLOTYPE: SOLOMON IS, GUADALCANAL, Gold Ridge, 800m, 23.vi.1956, J.L. Gressitt (worker). PARATYPE: BOUGAINVILLE (S), Guaba, 720m, 19.vi.1956, E.J. Ford Jr. (worker).