Polyrhachis aurora

Polyrhachis aurora is only known from two closely situated localities, Mt Elliot NP and the Paluma Ra., with all collections made in grassy open forests. Its nesting habit is unknown, but as all known specimens were collected foraging on the ground it can be assumed that P. aurora is a ground-nesting species, as are most other Australian Hagiomyrma.

Identification
A member of the ammon species-group in the Polyrhachis subgenus Hagiomyrma. Kohout (2013) - Polyrhachis aurora is characterised by distinctly posteriorly converging lateral margins of the promesonotal dorsum and strongly divergent propodeal spines. It closely resembles Polyrhachis trapezoidea which shares posteriorly contracted (‘trapezoidal’) pronotal and mesonotal dorsa and relatively dark, somewhat brassy-coloured pilosity and pubescence. Polyrhachis aurora differs from P. trapezoidea in having the propodeal spines more divergent and the petiole with a very narrowly rounded dorsum (Fig. 1G-H). In contrast, the propodeal spines in P. trapezoidea are only weakly divergent and the dorsum of petiole is a relatively wide, posteriorly sloping platform (Fig. 13G-H). Also, the bright red pubescence that covers most of the gastral dorsum in P. aurora, is limited to a rather narrow median patch in P. trapezoidea.

Distribution based on Regional Taxon Lists
Australasian Region: Australia.

Castes
Known only from the worker caste.

Nomenclature

 *  aurora. Polyrhachis (Hagiomyrma) aurora Kohout, 2013: 506, figs. 1G-H (w.) AUSTRALIA.

Worker
(holotype cited first): TL c. 7.41, 6.80-7.71; HL 1.87, 1.75- 1.93; HW 1.40, 1.37-1.47; CI 75, 75-80; SL 2.34, 2.28-2.40; SI 165, 159-167; PW 1.40, 1.28-1.45; MW 0.65, 0.62-0.75; PMI 215, 185-215; MTL 2.53, 2.43-2.71 (11 measured).

Anterior clypeal margin with denticulate, median flange. Clypeus with raised median carina, sinuate in profile, posteriorly rounding into well impressed basal margin. Frontal carinae sinuate with moderately raised margins; central area with weakly impressed frontal furrow. Sides of head in front of eyes straight, before rounding into mandibular bases; behind eyes, sides widely rounding into convex occipital margin. Eyes convex, in full face view clearly breaking lateral cephalic outline. Ocelli lacking. Pronotal dorsum flat anteriorly, convex towards promesonotal suture; humeri rounded with distinctly raised margins, shallowly concave dorsally; lateral margins of promesonotum distinctly converging posteriorly (PMI >185) and weakly raised before rounding into poorly indicated metanotal groove. Propodeum with lateral margins terminating in horizontal, distinctly divergent, acute spines. Petiole with anterior face straight, posterior face strongly convex; dorsum shallowly concave with pair of laterally elevated and posteriorly curved, acute spines. Anterior face of first gastral segment widely rounding onto dorsum of gaster.

Mandibles finely, longitudinally striate with numerous piliferous pits. Clypeus very closely punctate; head reticulate-punctate, genae distinctly more coarsely sculptured. Mesosoma and petiole more finely reticulate-punctate; gaster finely shagreened. Mandibles with numerous, semierect, short, golden hairs near masticatory borders and closely appressed hairs towards bases. Anterior clypeal margin with several anteriorly directed setae. Clypeus, frontal carinae and vertex with a few pairs of rather short, erect hairs; several longer hairs on fore coxae and distinctly short hairs on venter of trochanters and femora. Numerous short, erect, golden hairs on dorsum of gaster; longer hairs around apex and on gastral venter. Closely appressed, mostly golden pubescence with distinctly brassy hue in various densities over most dorsal body surfaces but not hiding underlying sculpturation, except on gaster where it is rather abundant and with distinct reddish tint over most of gastral dorsum; pubescence more silvery on sides of head, mesosoma, petiole and gastral venter.

Black, with only mandibular masticatory borders, condylae, extreme tip of apical funicular segments and gastral apex, reddish brown.

Type Material


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

Etymology
Derived from the Latin word aurora, meaning dawn or morning, in reference to the distinctly bright reddish colour of the gastral pubescence.

Determination Clarifications
Polyrhachis aurora was listed as P. ‘Hagio 21’ by Kohout (2000: 200).

References based on Global Ant Biodiversity Informatics

 * Kohout R.J. 2013. Revision of Polyrhachis (Hagiomyrma) Wheeler, 1911 (Insecta: Hymenoptera: Formicidae: Formicinae). Memoirs of the Queensland Museum  Nature 56: 487577