Polyrhachis trapezoidea

Polyrhachis trapezoidea is relatively common in open eucalypt forests and savannah woodlands and, like most of other Hagiomyrma species, nests in the ground.

Identification
A member of the trapezoidea species-group in the Polyrhachis subgenus Hagiomyrma. Kohout (2013) - Polyrhachis trapezoidea is very similar to Polyrhachis aurora with the main distinguishing characters given in the remarks under the latter species.

Key to Polyrhachis Hagiomyrma group species

Distribution
The known distribution of P. trapezoidea extends from Torres Strait south to about Gladstone, with reports of its occurrence in the northern part of the Northern Territory (Andersen, 2000).

Distribution based on Regional Taxon Lists
Australasian Region: Australia.

Castes
Male evidently in NHMW. Immature stages (eggs, larvae in various stages of development and pupae) in QM spirit collection.

Nomenclature

 *  trapezoidea. Polyrhachis trapezoidea Mayr, 1876: 72 (w.q.m.) AUSTRALIA. Combination in P. (Hagiomyrma): Forel, 1915b: 108. Subspecies of ammon: Forel, 1915b: 108. Revived status as species: Emery, 1925b: 185; Taylor & Brown, D.R. 1985: 142.

Worker
Kohout (2013) - (syntypes cited first): TL c. 8.92-9.07, 7.61-9.42; HL 2.18-2.21, 1.87-2.21; HW 1.84, 1.53-1.90; CI 83-84, 80-85; SL 2.50-2.53, 2.15-2.71; SI 136-137, 128-140; PW 1.68, 1.37-1.78; MW 0.72-0.84; PMI 197-221; MTL 2.87-3.03, 2.50-3.21 (2+13 measured).

Anterior clypeal margin with denticulate, shallowly ‘V’-shaped emarginate, median flange. Clypeus with blunt median carina; almost straight in profile with virtually flat basal margin. Frontal carinae sinuate with weakly raised margins; central area relatively wide with distinct frontal furrow. Sides of head in front of eyes converging towards mandibular bases; behind eyes, sides narrowly rounding into weakly convex occipital margin. Eyes convex, in full face view marginally breaking lateral cephalic outline. Ocelli lacking. Pronotal and mesonotal dorsa distinctly converging posteriorly; pronotal humeri rounded with raised margins; promesonotal suture distinctly impressed, metanotal groove poorly indicated. Lateral margins of propodeum weakly divergent, terminating in more-or-less horizontal, acute spines with tips bent slightly outwards and upwards. Petiole with relatively wide, posteriorly sloping dorsum and horizontal, widely divergent, acute spines.

Mandibles finely, longitudinally striate with numerous piliferous pits. Head and mesosoma finely reticulate-punctate; gaster finely shagreened.

Mandibular masticatory borders with medium length, variously curved, golden hairs. Very short, erect, bristle-like golden hairs on dorsa of head, mesosoma and petiole; gaster with somewhat longer hairs, notably around apex and on venter. Mostly golden, closely appressed pubescence in various densities on most dorsal surfaces; pubescence distinctly medially radiating, denser and with somewhat brassy hue along dorsal midline of mesosoma, completely hiding underlying sculpturation. Dorsum of gaster with abundant, rather pale golden pubescence, progressively more silvery towards sides and venter; first gastral tergite medially with rather narrow, rich golden median patch that widens posteriorly.

Black, with only narrow reddish-brown band along mandibular masticatory borders.

Queen
Kohout (2013) - (syntype cited first): TL c. 9.68, 9.63-11.09; HL 2.18, 2.18-2.31; HW 1.72, 1.72-1.84; CI 79, 79-80; SL 2.31, 2.31-2.46; SI 134, 132-138; PW 1.96, 1.96-2.21; MTL 2.77, 2.81-2.90 (5 measured).

Apart from sexual characters, very similar to worker except: pronotal humeri bluntly angular; lateral margins slightly raised and weakly rounded posteriorly. Mesoscutum with dorsum flat, as wide as long in dorsal view; median line bifurcate anteriorly; parapsides only slightly raised posteriorly. Mesoscutellum flat, not elevated above dorsal plane of mesosoma. Propodeal dorsum convex with spines shorter than worker, subparallel and slightly bent downwards. Petiole as in worker with spines shorter. Sculpturation, pilosity, pubescence and colour virtually identical to worker.