Polyrhachis cydista

Polyrhachis cydista is a rainforest-dwelling and apparently ground-nesting species, endemic to Queensland's Wet Tropics. (Kohout 2008)

Identification
Kohout (2008) - P. cydista  is very similar to a complex of species including Polyrhachis hookeri, Polyrhachis lownei and Polyrhachis obscura. However, all four species can be easily distinguished with the following key.

Distribution based on Regional Taxon Lists
Australasian Region: Australia.

Nomenclature

 *  cydista. Polyrhachis cydista Kohout, 2008c: 167, figs. 2, 5, 6 (w.q.) AUSTRALIA.

Worker
(holotype cited first) TL c. 5.24, 4.28-5.59; HL 1.40, 1.15-1.47; HW 1.31, 1.06-1.37; CI 93, 90-97; SL 1.37, 1.15-1.43; SI 104, 100-109; PW 1.40, 1.18-1.50; MTL 1.40, 1.15-1.50 (27 measured).

Anterior clypeal margin with shallow, medially notched flange, flanked by blunt denticles. Clypeus with blunt median carina, sinuate in profile; basal margin moderately impressed. Frontal carinae sinuate, with raised, laminate margins, separated by rather wide central area; frontal furrow replaced by anteriorly raised, longitudinal carina. Sides of head in front of eyes strongly converging towards mandibular bases; behind eyes immediately rounding into convex occipital margin. Eyes weakly convex, only marginally exceeding lateral cephalic outline in full face view. Ocelli lacking. Mesosoma laterally marginate along its entire length, convex in profile. Pronotal humeri angulate, dorsally concave, with anterior and lateral margins transluscent, narrowly raised and widely laminate. Promesonotal suture distinct; mesonotum with lateral margins converging posteriorly; metanotal groove distinct laterally, rather indistinct medially. Propodeum armed with strong, horizontal, laterally and posteriorly curved, acute spines; spines relatively wide and dorsally flattened in basal halves and distinctly narrowed and slender towards tips. Petiole very slender in side view with anterior and posterior faces converging towards rather acute, transversely convex and posteriorly bowed dorsum, armed with a pair of dorsolaterally diverging spines. Anterior face of first gastral segment distinctly higher than full height of petiole, widely rounding onto dorsum of gaster.

Mandibles finely, longitudinally striate. Clypeus irregularly, longitudinally reticulate-striate. Head mostly longitudinally striate, with sides reticulaterugose. Pronotal dorsum with somewhat wide, inversely U-shaped striae medially and oblique striae across humeral angles. Mesonotal and propodeal dorsa more-or-less longitudinally striate-punctate, with sides and propodeal declivity mostly horizontally wrinkled. Apical halves of propodeal and petiolar spines, anterior and posterior faces and dorsum of petiole, smooth and highly polished. Gaster finely reticulate-punctate.

Mandibles with numerous, relatively long, curved, golden hairs. Anterior clypeal margin with a few longer setae medially and several short setae laterally. Head, mesosoma, petiole and gaster with numerous long hairs, some almost twice as long as greatest diameter of eyes; hairs on head and mesosoma erect or variously curved, those on dorsum of gaster more posteriorly curved. Antennae and legs with numerous, short to medium length, erect, golden hairs. Very short, mostly suberect, grey and silvery hairs, rather dense on clypeus and propodeal declivity. Closely appressed, mostly silvery pubescence on dorsum of head, mesosoma and petiole, with distinct reddish tint on mesonotal and propodeal dorsa. Gastral dorsum with relatively long, appressed, rich brassy-golden to somewhat coppery pubescence; rather diluted and more silvery pubescence on sides and venter of gaster.

Head, mesosoma and petiole black; antennae, pronotal humeri and legs, including middle and hind coxae, very light orange; fore coxae and subpetiolar process medium reddish-brown, mandibles a shade darker; dorsum of gaster black, sides and venter very dark reddish-brown.

Queen
TL c. 6.10; HL 1.47; HW 1.31; CI 89; SL 1.37; SI 104; PW 1.56; MTL 1.49 (1 measured).

Very similar to worker and apart from differences due to full sexuality, including three ocelli, complete thoracic structure and wings, differing as follows: eyes larger; pronotal humeri bluntly angulate with only anterior margins narrowly laminate; mesoscutum wider than long, with widely rounded anterior margin in dorsal view; median line very short; parapsides flat, only very weakly raised posteriorly; mesoscutum in profile with rather low anterior face and flat dorsum; mesoscutellum flat, not elevated above dorsal plane of mesoscutum; propodeum and petiole with spines similar to those in worker, but shorter; dorsum of mesosoma with rather irregular, reticulate-punctate sculpturation; pilosity and colour virtually identical to worker.

Type Material
Types. Holotype worker, Queensland: Mt Hedley, 1-2 km N of Home Rule, 15°45'S, 145°17'E, 200-300 m, 11.vi.1996, rf, R.J. Kohout ace. 96.44. Paratypes: 7 workers, queen, same data as holotype. Holotype (QMT 152089), paratype worker and paratype queen in ; 2 paratype workers each in, and.

Determination Clarifications
Listed as P.”'Chario 04” by Kohout (2000: 193).

References based on Global Ant Biodiversity Informatics

 * Kohout R. J. 2008. Two new species of Polyrhachis Fr. Smith (Hymenoptera: Formicidae: Formicinae) from Australia, based on formerly quadrinomial taxa. Australian Entomologist 35: 161-171