Polyrhachis bicolor species-group

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 * Polyrhachis

This species in this group are members of the subgenus Myrmhopla.

Species

 * Polyrhachis bicolor
 * Polyrhachis nigripes
 * Polyrhachis subfossa

Kohout 2008a provides details about specimens that represent 5 putative new species, all from Sulawesi and closely related to Polyrhachis bicolor, that require additional material to properly assess their taxonomy.

Overview
The Polyrhachis bicolor species-group was established by Dorow (1995) who subdivided the former P. dives -group (as delimited by Emery, 1925) and transferred many of its original constituents into three, earlier established groups (P. armata -, sexspinosa - and viehmeyeri-groups), or into five groups he newly proposed (P. arachne -, bicolor-, cephalotes-, hector- and mucronata-groups). As presently defined, the bicolor-group includes only four species. However, about 11 infraspecific forms are currently associated with the name-bearing species, P. bicolor. Many of these forms apparently represent valid species and, in addition, at least twice as many closely related new species are in collections awaiting description. This relatively small, but widespread and complicated group is in great need of revision.

(see the subgenus page for more information about the species groups referenced above)

Worker
(modified from Dorow, 1995) Mostly small to medium-sized ants (HL 1.15-1.85) with general characteristics of the genus. Mandibles smooth or very finely, longitudinally striate, rather polished with small piliferous pits towards bases. Anterior clypeal margin with shallow, central, medially emarginate flange, laterally flanked by teeth or acute angles. Head semicircular in side view, oval in frontal view; genae immarginate. Eyes moderately to strongly convex, clearly exceeding lateral cephalic outline in full face view. Mesosoma totally immarginate, armed with rather slender spines. Petiole nodiform with a pair of lateral spines usually embracing first gastral segment, without intercalary spines or teeth. Antennal scapes and tibiae slender and long, spider-like. Sculpturation of head, mesosoma and petiole mostly a fine punctation, usually obscured by rich pubescence, producing a matt appearance. Gaster shagreened or finely reticulate-punctate, opaque. All body surfaces with abundant, relatively long, erect hairs and silvery to golden, appressed or suberect pubescence. Body bicoloured, mostly black with gaster and appendages light reddish-brown or amber-coloured (as in P. bicolor), or virtually unicoloured with body black and gaster, including appendages, black or very dark reddish-brown (as in Polyrhachis longipes).

Queen
Apart from sexual characters, very similar to worker. Armament of pronotum, propodeum and petiole distinctly reduced with spines shorter and stronger. Sculpturation, pilosity and colour virtually identical to worker.

Distribution and biology
Polyrhachis bicolor-group species are distributed throughout south-east Asia, including Myanmar, India, Thailand, Malaysia, Singapore, Vietnam and the Philippines, extending south to Indonesia, New Guinea and northern Australia. Members of the bicolor-group are arboreal nesters, building polydomous nests of silk and vegetation debris among the leaves of mostly rainforest trees and shrubs (Robson & Kohout, 2007).