Polyrhachis ammonoeides

Polyrhachis ammonoeides is a ground nesting species with its distribution limited to a relatively narrow band of coastal northwestern Australia, from Dampier in the north almost to Perth in the south.

Identification
A member of the ammon species-group in the Polyrhachis subgenus Hagiomyrma.

Key to Polyrhachis Hagiomyrma group species

Distribution based on Regional Taxon Lists
Australasian Region: Australia.

Castes
Males in ANIC spirit collection. Immature stages unknown.

Nomenclature

 *  ammonoeides. Polyrhachis ammonoeides Roger, 1863a: 157 (w.) AUSTRALIA. Combination in P. (Hagiomyrma): Forel, 1915b: 108. Subspecies of ammon: Forel, 1879a: 116. Revived status as species: Dalla Torre, 1893: 258. Senior synonym of chalchas: Kohout, 1994a: 135.
 * chalchas. Polyrhachis chalchas Forel, 1907h: 307 (w.q.) AUSTRALIA. Combination in P. (Hagiomyrma): Forel, 1915b: 108. Junior synonym of ammonoeides: Kohout, 1994a: 135.

Worker
Kohout (2013) - (lectotype cited first): TL c. 8.0, 6.65- 8.52; HL 1.98, 1.65-2.09; HW 1.53, 1.34-1.65; CI 77, 77-82; SL 2.28, 2.09-2.56; SI 149, 146-164; PW 1.34, 1.05-1.50; MW 0.81-0.88; PMI 147-164; MTL 2.65, 2.46-3.12 (25 measured).

Median flange of anterior clypeal margin irregularly jagged with one central tooth and rather blunt lateral angles. Clypeus with median, longitudinal carina, sinuate in profile. Frontal carinae with distinctly raised margins; central area relatively wide, weakly raised medially. Sides of head in front of eyes converging anteriorly in virtually straight line; behind eyes, sides widely rounding into convex occipital margin. Eyes convex, marginally breaking lateral cephalic outline in full face view. Ocelli lacking, only rudimentary lateral ocelli indicated in some specimens. Pronotal dorsum wider than long; humeri narrowly rounded with shallow depression dorsally; lateral margins behind humeri sinuate, distinctly raised and only weakly converging towards promesonotal suture. Lateral margins of mesonotum converging posteriorly in gentle curve towards metanotal groove indicated by weakly impressed, posteriorly bowed line. Propodeum with lateral margins terminating in distinctly divergent, slender, acute spines. Petiole armed with pair of divergent, hook-shaped, acute spines.

Mandibles finely longitudinally striate with numerous piliferous pits towards bases. Head and mesosoma reticulate-punctate; sculpturation on vertex somewhat coarser with numerous shallow pits. Gaster finely shagreened.

Mandibles with medium length, curved, golden hairs at masticatory and outer borders; numerous closely appressed, shorter hairs towards mandibular bases. Several anteriorly directed, longer setae arising from median anterior clypeal margin, shorter setae fringing margin laterally. Long and medium length, golden, mostly erect hairs, some longer than greatest diameter of eyes, on clypeus, along frontal carinae and on vertex, numerous hairs fringing lateral outline of head in full face view. Short, erect hairs along leading edge of antennal scapes. Rather long, golden hairs abundant on most body surfaces, including propodeal declivity and spines, except apices. Hairs somewhat longer and posteriorly inclined on gaster, notably around apex and on venter. Closely appressed, rather sparse, mostly silvery pubescence on head, mesosoma, petiole and venter of gaster; longer, rich golden pubescence on gastral dorsum, completely hiding underlying sculpturation. Black with only mandibular teeth, apical funicular segments and legs dark to very dark reddish-brown.

Queen
Kohout (2013) - Dimensions: TL c. 9.68-10.43; HL 2.18- 2.21; HW 1.68-1.75; CI 76-79; SL 2.37-2.56; SI 139- 149; PW 1.96-2.12; MTL 2.93-2.99 (4 measured).

Apart from sexual characters, closely resembling worker except: pronotal dorsum with humeri rounded and indication of blunt humeral angles. Mesoscutum in dorsal view virtually as long as wide; anterior margin widely rounded in dorsal and lateral views; 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.

Determination Clarifications
Kohout (2013): Forel was apparently misled by the original type locality given by Roger as Port Jackson and redescribed P. ammonoeides from Western Australia as P. chalchas. He also misinterpreted the short description given by Roger and considered a series of specimens collected by E. Mjöberg at Laura, Queensland (MNHU) to be P. ammonoeides. However, after examining these specimens, I consider they represent the species Polyrhachis cracenta.