Polyrhachis pseudothrinax

Polyrhachis pseudothrinax appears to be somewhat more common than other species of the P. gravis-group. It ranges from north Queensland westwards across the Northern Territory to the Kimberley region of Western Australia.

Identification
Kohout (2013): Throughout its distribution, P. pseudothrinax is relatively morphologically uniform, however, the Queensland populations appear to have a longer antennal scapes (SI 118-126 versus 112-120 in NT populations), with the exception of a single specimen from Melville Island (SI 127). When describing this species, Hung (1967) also noted differences in sculpturation of the propodeal dorsum, however, following examination of numerous specimens across the whole range of this species it is apparent that the variability in striation is similar to that displayed by other species of the P. gravis-group. Some specimens also appear to differ in the shape and length of the propodeal dorsum (Andersen, personal communication), however, subsequent examination failed to reveal any other associated taxonomically important characters and I consider they represent only variants from the “prototype” of this species.

With its single middle petiolar spine, P. pseudothrinax is easily recognised. Only Polyrhachis unicornis shares this character, however, it differs in having the spine less acute and shorter (Fig. 5D, G) and in some specimens weakly emarginate apically. They also differ in the shape of their eyes which, in P. unicornis, are larger and distinctly less convex (Fig. 5C). In addition, the sculpturation on the pronotal dorsum is distinctly transverse in P. unicornis, while it is more-or-less longitudinal in P. pseudothrinax and the bristle-like pubescence is distinctly longer and rather abundant in P. pseudothrinax, while it is much shorter and rather sporadic in P. unicornis. Their colour patterns are very similar with a black body and very distinct, light reddish-brown or orange-coloured legs, however, the anterior portion of clypeus in P. unicornis is distinctly lighter reddish-brown, while it is black throughout in the other species.

Distribution based on Regional Taxon Lists
Australasian Region: Australia.

Castes
Male and immature stages unknown.

Nomenclature

 *  pseudothrinax. Polyrhachis pseudothrinax Hung, 1967a: 199, figs. 1-6 (w.) AUSTRALIA. Combination in P. (Campomyrma): Kohout & Taylor, 1990: 512.

Worker
Kohout (2013) - (holotype cited first, paratype second): TL c. 8.37, 8.47, 7.00-9.22; HL 2.06, 2.06, 1.72-2.25; HW 1.75, 1.72, 1.43-2.01; CI 85, 83, 83-90; SL 2.09, 2.12, 1.81-2.34; SI 119, 123, 112-127; PW 1.62, 1.62, 1.31-1.87; MIL 2.65, 2.65,2.25-2.90 (1+1+18 measured).

Queen
Kohout (2013) - TL c. 9.42; HL 2.21; HW 1.81; CI 82; 5L 2.15; SI 119; PW 2.06; MTL 2.81 (1 measured).

Queen very similar to worker with usual characters identifying full sexuality, including three ocelli, complete thoracic structure, wings and distinctly larger eyes. Pronotal humeri armed with distinct, somewhat dorsally flattened teeth. Mesoscutum marginally wider than long with widely rounded anterior margin in dorsal view; median line distinct; parapsides flat; anterior face in profile rounding onto relatively low, flat dorsum. Mesoscutellum only marginally elevated above dorsal plane of mesosoma. Propodeal dorsum with lateral margins strongly converging posteriorly, terminating in upturned, dorsolaterally directed, acute teeth; dorsum between them descending into steep declivity in medially uninterrupted line. Petiole very similar to worker, only median spine distinctly shorter. Sculpturation, pilosity and colour scheme virtually as in worker.

Type Material


Both the and  "claim" to have the holotype.