Polyrhachis ammon

Polyrhachis ammon is a widespread and relatively common, ground-nesting species, mostly occuring in open eucalypt forests along the eastern Australian seaboard. It ranges from northern Queensland south to Victoria and as far inland as the Australian Capital Territory, however, it becomes rather uncommon towards the northern limit of its distribution.

Identification
A member of the ammon species-group in the Polyrhachis subgenus Hagiomyrma. Kohout (2013): Polyrhachis ammon closely resembles Polyrhachis uncaria, however, they differ in numerous characters, discussed in the remarks section under P. uncaria.

Throughout its range P. ammon forms numerous, more-or-less overlapping populations that often, to some extent, differ morphologically from the holotype. However, when specimens from across the entire distribution were compared, no taxonomically significant variability was evident and I believe that all the examined populations are conspecific.

Key to Polyrhachis Hagiomyrma group species

Distribution based on Regional Taxon Lists
Australasian Region: Australia.

Castes
Males and immature stages present in the QM and ANIC collections.

Nomenclature

 *  ammon. Formica ammon Fabricius, 1775: 394 (w.) AUSTRALIA. Mayr, 1876: 72 (q.m.); Imai, Crozier & Taylor, 1977: 347 (k.). Combination in Polyrhachis: Smith, F. 1858b: 73; in P. (Hagiomyrma): Wheeler, W.M. 1911c: 860. Senior synonym of angustata: Kohout, 1988c: 430.
 * angustata. Polyrhachis ammon var. angustata Forel, 1902h: 525 (w.) AUSTRALIA. Combination in P. (Hagiomyrma): Emery, 1925b: 184. Junior synonym of ammon: Kohout, 1988c: 430.

Worker
Kohout (2013) - (holotype cited first): TL c. 9.07, 7.91-9.83; HL 2.22, 1.96-2.31; HW 1.78, 1.56-1.91; CI 80, 78-85; SL 2.67, 2.42-2.97; SI 150, 141-159; PW 1.51, 1.39-1.72; MW 0.94-1.09; PMI 135- 159; MTL 3.17, 2.81-3.43 (37 measured).

Median flange of anterior clypeal margin with distinct, acute teeth medially, laterally flanked by acute angles. Clypeus with median, posteriorly raised, longitudinal carina; sinuate in profile. Frontal carinae with only moderately raised margins; central area relatively wide with flat frontal furrow. Sides of head in front of eyes converging anteriorly in virtually straight line, behind eyes sides rounding into moderately convex occipital margin. Eyes situated close to occipital corners, convex, marginally breaking lateral cephalic outline in full face view. Ocelli lacking. Pronotal dorsum wider than long, humeri distinctly rounded, weakly dilated and shallowly concave dorsally; lateral margins behind humeri usually shallowly emarginate or notched, weakly converging towards promesonotal suture. Mesonotum with lateral margins converging posteriorly into dorsally indistinct metanotal groove. Propodeum with lateral margins divergent, terminating in broad-based, horizontal, subparallel or weakly divergent acute spines, tips weakly turned outwards; declivity steep, convex in profile. Petiole armed with a pair of horizontal, divergent, acute spines.

Mandibles finely longitudinally striate with numerous piliferous pits towards bases. Head and mesosoma finely reticulate-punctate, sculpturation on vertex and sides of head more distinct and organised into more-or-less longitudinal striae. Gaster finely shagreened. Mandibles with medium length, curved, golden hairs at masticatory and outer borders; numerous closely appressed, shorter hairs towards mandibular bases. Only a few anteriorly directed setae fringing anterior clypeal margin. Several short to medium length, erect hairs on clypeus, along frontal carinae and vertex, no hairs breaking lateral outline of head in full face view. Numerous, medium length, erect golden hairs on most body surfaces, including upper part of propodeal declivity; hairs somewhat longer and posteriorly inclined on gaster, notably around apex and on venter. Closely appressed, mostly silvery or pale golden pubescence rather sparse on head, more abundant on sides of mesosoma, propodeal dorsum, petiole and venter of gaster. Rather abundant, mostly rich golden, with distinct brassy hue, somewhat medially radiating pubescence along promesonotal midline and on gastral dorsum where it virtully hides underlying sculpturation.

Black with only mandibular teeth and condylae reddish-brown.

Queen
Kohout (2013) - TL c. 9.78-11.14; HL 2.12-2.37; HW 1.75-1.96; CI 81-86; SL 2.37-2.77; SI 133-148; PW 2.02-2.37; MTL 2.87-3.22 (17 measured).

Queen similar to worker with usual characters identifying full sexuality. Pronotal dorsum with humeri widely rounded, shallowly concave dorsally along narrowly raised margins. Mesoscutum almost as long as wide; anterior margin evenly rounded; median line distinct, parapsides rather flat; mesoscutum and mesoscutellum uniformly flat in lateral view. Propodeal and petiolar spines similar to those in worker, but distinctly shorter. Sculpturation, pilosity, pubescence and colour virtually identical to worker.