Polyrhachis queenslandica

This species is an arboreal nester, using silk to join the leaves of various lowland rainforest trees and shrubs (Kohout 1999, 2000; Robson & Kohout 2005, 2007; Kohout, 2012).

Identification
As indicated by Kohout (1994), the most obvious differences between Polyrhachis delicata and P. queenslandica are their colour and the orientation of their propodeal spines. However, due to a high degree of variability, notably within Queensland populations of both species, these characters can be unreliable and, while both species are usually separable, no single character is universally diagnostic. The propodeal spines in P. delicata are generally more strongly upturned, but the actual angle of elevation varies between specimens, even those of the same nest series. The propodeal spines in P. queenslandica are distinctly less elevated with only a small amount of variation between the specimens examined. The colour of the body appears to be a more reliable character to separate the species but only in fully pigmented specimens. A mostly red or reddish-brown mesosoma, gaster and appendages, contrasting with a darker head (almost black in some specimens) characterises P. delicata, while the body in P. queenslandica is mostly uniformly black or very dark reddish-brown. The sculpturation of the head and mesosoma in P. delicata is rather distinctly reticulate-punctate and opaque, while it is markedly more finely and closely punctate in P. queenslandica. The petiolar node in P. delicata is relatively slim and distinctly narrows dorsally in lateral view, with the anterior face smoothly curving onto the petiolar dorsum in an uninterrupted line that incorporates the anterior edge of the dorsoposteriorly elevated median spine. In contrast, the petiolar node in P. queenslandica is distinctly thicker in lateral view, with the anterior face curving onto a virtually flat dorsum and the median petiolar spine dorsoposteriorly elevated at a distinctly steeper angle. The latter character does not serve to separate the queens of the two species, however, the median petiolar spine in the queen of P. queenslandica is simply pointed, while its apex is clearly emarginated in P. delicata.

Distribution based on Regional Taxon Lists
Australasian Region: Australia. Indo-Australian Region: New Guinea.

The distribution of P. queenslandica is divided between New Guinea and northern Queensland, where it overlaps with Polyrhachis delicata. The syntypes of the synonym P. dahli unisculpta, collected at Wareo on Huon Peninsula, and a single worker from Kokoda, are the only known records of the species from New Guinea. In Australia it is relatively common, though somewhat less abundant than P. delicata, particularly towards the southern limit of its distribution. The known Australian range extends from the tip of Cape York Peninsula south to about the Paluma Range.

Castes
Males and immature stages (eggs, larvae and pupae) in QM spirit collection. (Kohout 2012)

Nomenclature

 *  queenslandica. Polyrhachis queenslandica Emery, 1895g: 356 (w.) AUSTRALIA. Crawley, 1921: 96 (q.m.). Combination in P. (Myrmothrinax): Emery, 1925b: 183. Senior synonym of unisculpta: Kohout, 1998: 510. See also: Kohout, 2012: 53.
 * unisculpta. Polyrhachis dahli var. unisculpta Viehmeyer, 1914b: 48 (w.q.) NEW GUINEA. Combination in P. (Myrmothrinax): Emery, 1925b: 183. Junior synonym of queenslandica: Kohout, 1998: 510.

Worker
Kohout (2012) - (syntypes [5] cited first): TL c. 5.95-6.70, 5.09-6.71; HL 1.50-1.65; 1.34-1.65; HW 1.26-1.42, 1.15-1.47; CI 82-88, 82-89; SL 1.90-2.03, 1.72-2.12; SI 141-153, 141-155; PW 0.87-0.97, 0.75- 1.00; MTL 2.06-2.28, 1.78-2.40 (74 measured).

Anterior clypeal margin with wide median truncation flanked by small teeth. Clypeus with median carina; straight in profile, posteriorly rounding into moderately impressed basal margin. Frontal triangle distinct. Frontal carinae sinuate with margins only weakly raised at midlength; central area weakly convex with poorly indicated frontal furrow. Sides of head in front of eyes converging towards mandibular bases in weakly convex line; behind eyes sides widely rounding into convex occipital margin. Eyes convex, in full face view clearly breaking lateral cephalic outline. Ocelli lacking; position of lateral pair indicated in some specimens by shallow punctures in sculpturation. Pronotal dorsum often with poorly defined median longitudinal depression; pronotal humeri angular with lateral margins converging posteriorly into distinct promesonotal suture. Dorsum of mesosoma with lateral margins converging posteriorly into well defined metanotal groove. Lateral margins of propodeum subparallel, terminating in obliquely elevated, subparallel, acute spines. Petiole with anterior face straight, posterior face weakly convex; petiolar dorsum a virtually flat platform, armed with two widely diverging, short lateral spines and a long, acute, dorsoposteriorly elevated median spine. Anterior face of first gastral segment distinctly higher than full height of petiole, widely rounding onto gastral dorsum.

Mandibular bases finely longitudinally striate-rugose, sculpture distinctly finer and polished towards masticatory borders. Head mostly finely reticulate-punctate, feebly polished. Intensity of sculpturation somewhat increasing posteriorly, with mesosoma and petiole more closely and distinctly reticulate-punctate. Gaster very finely shagreened, highly polished.

Mandibular masticatory borders with several, semierect, golden hairs and very short, closely appressed hairs towards bases. Anterior clypeal margin with a fringe of a few, rather short setae; clypeus with pair of relatively short hairs near anterior and basal margins; slightly longer, semierect hairs along frontal carinae, on vertex and front coxae. Pilosity and pubescence almost completely absent from mesosoma and petiole. Gastral venter and apical gastral tergites with numerous, relatively long hairs. Dorsum of gaster with very short, closely appressed, much diluted golden pubescence.

Colour. Head and body in fully pigmented specimens mostly black or very dark reddish-brown. Mandibles, except masticatory borders, clypeus and central area, legs, including coxae and base of gastral dorsum usually dark reddish-brown; funicular segments progressively lighter, yellowish-brown, towards antennal apex. Mandibular masticatory borders, anterior clypeal margin and frontal carinae narrowly lined with black or very dark brown.

Queen
Kohout (2012) - TL c. 8.11-9.17; HL 1.87-1.96; HW 1.59-1.68; CI 84-87; SL 2.25-2.34; SI 134-144; PW 1.58-1.68; MTL 2.46-2.59 (10 measured). Apart from sexual characters, closely resembling worker except: pronotal humeri obtusely angular. Mesoscutum about as wide as long, lateral margins converging anteriorly and forming moderately rounded anterior margin; median line distinct, bifurcate dorsally; parapsides flat, only marginally raised posteriorly. In profile, anterior face of mesoscutum widely rounding onto weakly convex dorsum. Mesoscutellum raised above dorsal plane of mesosoma, strongly rounding posteriorly into distinctly impressed metanotal groove. Propodeal dorsum with lateral margins indistinct; propodeal spines somewhat flattened dorsally, about as long as distance between their bases, oblique to main axis of body; their inner margins continued medially and forming an open ‘U’ in anterior view. Petiole with anterior face rounding onto posteriorly elevated dorsum; spines shorter and thicker than in worker; middle spine only marginally longer than lateral pair, acute.

Type Material
Polyrhachis queenslandica type material.

Syntype workers. Type locality: AUSTRALIA, QUEENSLAND, Kamerunga (M. Podenzana),, (examined by Kohout, 2012).

Polyrhachis dahli unisculpta type material.

Syntype workers. Type locality: NEW GUINEA, Huon Pen., Wareo, (examined by Kohout, 2012).