Polyrhachis thusnelda

Inhabits open eucalypt forests, but has also been collected from the canopy of lowland tropical rainforest. For information on the lithocolous nesting habit of P. thusnelda, see Robson & Kohout (2005: 164-169).

Identification
A member of the trapezoidea species-group in the Polyrhachis subgenus Hagiomyrma. Kohout (2013) - Polyrhachis thusnelda is easily recognised by a combination of a flat-topped petiolar dorsum, most of the body covered with long hairs and a black body strongly contrasting with rich golden pubescence on the gastral dorsum.

Key to Polyrhachis Hagiomyrma group species

Distribution
This is a relatively widespread species with a patchy distribution from Cape York Peninsula south to about Mackay, Queensland. However, it becomes rather uncommon towards the northern limits of its range.

Distribution based on Regional Taxon Lists
Australasian Region: Australia.

Castes
Males evidently in MHNG collection. Immature stages present in the QM spirit collection.

Nomenclature

 *  thusnelda. Polyrhachis thusnelda Forel, 1902h: 509 (w.q.m.) AUSTRALIA. Combination in P. (Hagiomyrma): Emery, 1925b: 185.

Worker
Kohout (2013) - (syntypes cited first): TL c. 8.62-8.92, 8.16-9.12; HL 2.00-2.03, 1.93-2.15; HW 1.81-1.84, 1.75-2.00; CI 90-91, 90- 94; SL 2.25-2.28, 2.21-2.46; SI 124, 118-125; PW 1.78-1.84, 1.72-2.01; MW 1.09-1.12, 1.00-1.28; PMI 159-169, 156-172; MTL 2.56-2.59, 2.43-2.84 (6+16 measured).

Anterior clypeal margin with very shallow, denticulate, median flange, laterally flanked by acute teeth. Clypeus straight in profile with only weakly raised median carina; basal margin flat. Frontal triangle indistinct. Frontal carinae sinuate, with moderately raised margins; central area wide with distinct frontal furrow. Sides of head in front of eyes converging towards mandibular bases in weakly convex line; behind eyes, sides narrowly rounding into weakly convex occipital margin. Eyes convex, in full face view not or only marginally exceeding lateral cephalic outline. Ocelli lacking. Pronotal humeri shallowly concave; pronotal dorsum with moderately raised margins converging into distinct promesonotal suture. Mesosomal margins converging into weakly impressed metanotal groove. Propodeum armed with broad-based, relatively short, divergent spines. Petiole with anterior and posterior faces subparallel; dorsum with distinct, flat platform, laterally armed with horizontal, divergent, acute spines. Anterior face of first gastral tergite widely rounding onto dorsum.

Mandibles finely longitudinally striate with numerous piliferous pits. Head and mesosoma very closely, distinctly reticulate-punctate; pronotal dorsum with sculpture distinctly coarser, somewhat vermiculate-rugose in some specimens. Bases of spines sculptured, tips smooth and polished. Petiole with anterior face polished, posterior face deeply sculptured; dorsal platform distinctly reticulate. Gaster shagreened with dorsum more distinctly sculptured.

Mandibles at masticatory and outer borders with numerous curved, golden hairs. Anterior clypeal margin with a few longer, anteriorly projecting setae medially and several short setae fringing margin laterally. Head, mesosoma, petiole, gaster and venter of femora with numerous, mostly erect and variously curved, long silvery hairs, many distinctly longer than greatest diameter of eyes. Hairs on head more anteriorly directed with none breaking lateral cephalic outline between eyes and mandibular bases in full face view. Hairs lacking on antennal scapes, dorsal sufaces of femora, most of propodeal declivity and sides of mesosoma, except a few hairs on metapleurae. Closely appressed, silvery pubescence in various densities over most body surfaces, partly hiding underlying sculpturation; pubescence on gaster somewhat longer, silvery on sides and venter, rich golden on dorsum, completely hiding underlying sculpturation.

Black; mandibular teeth narrowly reddish-brown; antennal segments progressively lighter reddish-brown towards apices.

Queen
Kohout (2013) - TL c. 9.47-10.18; HL 2.12- 2.21; HW 1.84-2.00; CI 87-90; SL 2.21-2.28; SI 114- 120; PW 2.15-2.20; MTL 2.62-2.68 (4 measured).

Apart from sexual characters, very similar to worker except: pronotal humeri more-or-less subangular. Mesoscutum wider than long with anterior margin widely and evenly rounded in dorsal view; median line bifurcate towards flat dorsum; parapsides flat, only weakly raised posteriorly. Mesoscutellum flat, not elevated above dorsal plane of mesosoma. Spines distinctly shorter than in worker. Sculpturation, pilosity, pubescence and colour virtually identical to worker.