Polyrhachis darlingtoni

Polyrhachis darlingtoni is only known from two closely situated localities in the McIlwraith Range, along Leo Creek Road and at Lankelly Creek, near Coen on Cape York Peninsula.

Identification
A member of the trapezoidea species-group in the Polyrhachis subgenus Hagiomyrma. Kohout (2013) - Polyrhachis darlingtoni is easily identified by its low petiole with a strongly posteriorly descending, triangular dorsum and the bases of its rather short spines situated well below its widely rounded summit (Fig. 13B). The petiolar node of P. darlingtoni resembles that of Polyrhachis nourlangie, however in the latter species the petiolar dorsum is flat, laterally marginate, with the margins terminating in the bases of short, curved spines on the petiolar summit (Fig. 13D). The species also differ in their size, with P. darlingtoni consistently larger (HL 2.59-2.67 versus 1.62-2.09 in P. nourlangie), and in the colour of their pubescence which, in P. nourlangie is uniformly golden, lacking the brassy and reddish hues of P. darlingtoni.

Key to Polyrhachis Hagiomyrma group species

Distribution based on Regional Taxon Lists
Australasian Region: Australia.

Castes
Sexuals unknown. Immature stages (larva and eggs) in QM spirit collection.

Nomenclature

 *  darlingtoni. Polyrhachis (Hagiomyrma) darlingtoni Kohout, 2013: 565, figs. 13A-B (w.) AUSTRALIA.

Worker
(holotype cited first): TL c. 11.79, 10.50-11.79; HL 2.68, 2.52-2.68; HW 1.90, 1.79-1.96; CI 71, 71-73; SL 3.58, 3.28- 3.58; SI 188, 180-189; PW 1.56, 1.46-1.66; MW 1.09, 1.06-1.16; PMI 143, 142-152); MTL 4.33, 4.08-4.43 (9 measured).

Mandibles with 5 teeth, progressively reducing in length towards base. Anterior clypeal margin with median, shallowly emarginate, bluntly denticulate flange, laterally flanked by rather obtuse angles. Clypeus with median longitudinal carina; distinctly sinuate in profile, posteriorly rounding into impressed basal margin. Frontal carinae sinuate with moderately raised margins; central area with rather flat frontal furrow. Sides of head in front of eyes converging towards mandibular bases in very weakly convex line; behind eyes, sides rounding into occipital margin. Eyes convex, in full face view marginally breaking lateral cephalic outline. Ocelli lacking, positions indicated in some specimens by shallow pits in cephalic sculpture. Pronotal humeri narrowly rounded; dorsum almost quadrate with lateral margins very weakly converging anteriorly in some specimens and somewhat irregularly notched before their midlength; promesonotal suture deeply impressed. Mesonotum with lateral margins converging posteriorly towards distinct metanotal groove. Propodeal dorsum with lateral margins terminating in subparallel, somewhat sinuate, acute spines. Petiolar node markedly broad and low in lateral view, with anterior face rounding onto flat, strongly posteriorly descending triangular dorsum; spines very short, weakly divergent, bases situated well below apex of dorsal convexity. Anterior face of first gastral segment widely rounding onto dorsum.

Mandibles finely longitudinally striate with numerous piliferous pits. Head and mesosoma finely reticulate-punctate, vertex of head and pronotal dorsum somewhat polished, mesonotum and propodeum opaque; tips of spines highly polished. Gaster shagreened.

Mandibles with numerous, semierect, curved, golden hairs. Medium length, erect hairs on clypeus, along frontal carinae and on vertex, numerous erect hairs fringing outline of head in full face view. Long, erect or semierect, rather abundant, golden hairs on dorsum of mesosoma, coxae, venter of femora, petiole and gaster, most hairs as long as greatest diameter of eyes. Silvery appressed pubescence in various densities over most body surfaces, except vertex of head and pronotal dorsum where it is golden and sporadic; distinctly medially radiated pubescence with brassy tint abundant on mesonotal dorsum. Gastral dorsum with pubescence virtually hiding underlying sculpturation, golden with reddish hue along midline, silvery on sides and venter of gaster.

Black throughout with only mandibular teeth and condylae dark reddish-brown.

Type Material


Type deposition: Holotype and 6 paratypes in ; 4 paratypes each in  and, 2 paratypes each in , , ,  and NMNH.

Etymology
Named in honour of the late Philip J. Darlington, former professor at Harvard University, Cambridge and eminent entomologist and biogeographer, who collected many Polyrhachis species and other insects during the 1932 and 1956- 1958 Australia Harvard Expeditions.