Polyrhachis ignota

Nothing is known about the biology of this species.

Identification
Kohout 1987: This is the third Polyrhachis sexspinosa-group species from Philippines which lacks hairs on the antennal scapes (the others are Polyrhachis magnifica and Polyrhachis scabra). P. ignota differs from magnifica in having erect hairs present on the extensor surfaces of the middle and hind tibiae and in the structure of the pronotal spines. In P. ignota these are quite short, and only weakly curved, while in P. magnifica they are long and strongly curved forward. P. ignota differs from P. scabra in having a strongly produced pronotal dorsum, which is only moderately convex in scabra.

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

Images from AntWeb
Queens and males are unknown.

Nomenclature

 *  ignota. Polyrhachis ignota Kohout, 1987: 171, figs. 7, 10, 13 (w.) PHILIPPINES.

Worker
Dimensions (holotype cited first): TL 14.36, 13.26-14.97; HL 3.48, 3.17-3.43; HW 2.07,1.86-2.07; CI 59, 59-60; SL 4.54, 4.43-4.48; SI 219, 216-238; PW 1.81, 1.66-1.81; MTL 6.20, 5.90-6.20 (3 measured).

Mandibles with 5 teeth. Clypeus carinate, sinuate in profile (convex above and concave below). Sides of head in front of eyes only feebly convex, almost straight; strongly narrowed behind eyes. Occipital margin narrow, collar-like, without lateral angular prominences. Antennal carinae elevated, sinuate. Antennal scapes extending beyond occipital border by nearly half their length. Eyes convex. Pronotum strongly convex, distinctly swollen (though not to such a degree as in P. exotica); pronotal spines stout, projecting laterally, only slightly curved forward. Mesonotal dorsum in profile feebly convex, propodeum shallowly concave, declivity abrupt. Metanotal groove replaced by a minutely raised ridge. Mesopleural process represented as a non-acute simple lobe. Propodeal spines elevated at their bases, divergent and recurved. Petiole relatively low in front; its dorsum shallowly concave in profile, sloping anteriorly, and with a weak median longitudinal ridge similar to that in P. osiris. Apices of petiolar spines scarcely elevated, the spines short. Gaster, when contracted, short, broadly ovate.

Mandibles smooth and shining at the masticatory border, densely punctate at their bases, intervening surfaces with graded sculpturation. Clypeus and front of head finely reticulate-punctate; sculpturation increasing posteriorly in intensity and density, so that the dorsal face and lateral branches of occiput are somewhat coarsely rugose. Mesosomal dorsum with weak rugosity, decreasing posteriorly in intensity and density. Gaster very finely reticulate-punctate.

White or yellowish erect hairs present in variable density all over the body and appendages, but absent from the antennal scapes. Relatively long, suberect, somewhat radiating rich golden pubescence variously developed; most dense on head and mesosomal dorsum, rather diluted on lateral portions of mesosoma (the specimens might be somewhat worn). Gastral pubescence ranging from yellow on anterodorsal aspect of first tergite to silvery white elsewhere, arranged in a characteristic midline pattern.

Type Material
Holotype and 1 paratype in BPBM; 1 paratype in RJK.