Polyrhachis cracenta

Like most Hagiomyrma species, this species is a ground-nesting species, apparently preferring the bases of trees as nesting sites (‘nest at base of small sapling’ [G.F. Hill]; ‘extensive diggings all round small paperbarks’ [B.B. Lowery]).

Polyrhachis cracenta is one of several Polyrhachis species which were originally collected at Townsville and other north Queensland localities by F.P. Dodd and other early collectors and were subsequently located in the Northern Territory (i.e. Polyrhachis lysistrata, Polyrhachis prometheus and Polyrhachis incerta (= ‘P. micans ops rufa’ Crawley).

Identification
A member of the ammon species-group in the Polyrhachis subgenus Hagiomyrma. Kohout (2013) - Polyrhachis cracenta is very similar to Polyrhachis crawleyi but is easily separated by its consistently larger size (HL 1.93-2.12 in P. cracenta versus 1.66-1.84 in P. crawleyi) and its unique superficially glabrous appearance. It is evidently a rare species that has been collected only on a few occasions. Specimens collected by Mjöberg near Laura on Cape York Peninsula, were erroneously identified by Forel (1915) as Polyrhachis ammonoeides Roger and as a result, he described a closely similar species, P. crawleyi, as a variety of P. ammonoeides.

Key to Polyrhachis Hagiomyrma group species

Distribution based on Regional Taxon Lists
Australasian Region: Australia.

Castes
Males unknown. Immature stages (eggs, larvae and pupae) in QM spirit collection.

Nomenclature

 *  cracenta. Polyrhachis (Hagiomyrma) cracenta Kohout, 2013: 517, figs. 3C-D (w.q.) AUSTRALIA.

Worker
(holotype cited first): TL c. 11.09, 10.28-11.24; HL 2.56, 2.37-2.56; HW 2.03, 1.81-2.06; CI 79, 76-82; SL3.33, 3.07-3.33; SI 164, 157-178; PW 1.68, 1.48- 1.68; MW 1.27, 1.15-1.28; PMI 132, 122-139; MTL 4.33, 3.93-4.33 (26 measured).

Anterior clypeal margin with median, denticulate flange, laterally flanked by acute, laterally directed teeth. Clypeus with median carina; in profile shallowly concave anteriorly, straight posteriorly towards virtually flat basal margin. Frontal triangle shallowly impressed. Frontal carinae with raised margins; central area relatively wide and flat with frontal furrow replaced with weakly raised ridge. Sides of head in front of eyes converging towards mandibular bases in virtually straight line; behind eyes, sides converging into weakly convex occipital margin. Eyes situated close to occipital corners, convex, in full face view clearly exceeding lateral cephalic outline. Ocelli lacking. Pronotal dorsum with humeri moderately dilated, rounded with upturned margins; lateral margins behind humeri weakly notched in some specimens, parallel towards promesonotal suture. Mesonotal dorsum with posteriorly converging margins. Propodeum with lateral margins divergent, terminating in subparallel, acute spines, tips weakly turned outwards; propodeal dorsum widely rounding into distinctly convex propodeal declivity. Petiole with dorsum narrowly rounded, weakly convex medially, armed with divergent, acute spines. Anterior face of first gastral segment widely rounding onto dorsum.

Mandibles finely longitudinally striate with numerous piliferous pits. Head and mesosoma very finely and closely reticulate-punctate with sculpturation on sides of head somewhat more distinct. Gaster finely shagreened.

Mandibles with numerous medium length, golden hairs, distinctly longer at masticatory borders, shorter towards mandibular bases. Numerous, anteriorly directed setae fringing anterior clypeal margin. Several medium length hairs on clypeus, along frontal carinae and vertex, but no hairs breaking lateral outline of head in full face view. Several, medium length, semierect golden hairs on pronotal dorsum; long hairs, almost reaching greatest diameter of eyes in length, on anterior aspect of front coxae; somewhat shorter hairs on middle and hind coxae, below propodeal spiracles and on petiolar dorsum. Mesonotal and propodeal dorsa completely without hairs. Gaster with numerous, golden, posteriorly inclined hairs, longest on gastral venter and around apex, almost reaching greatest diameter of eyes in length. Very sparse, closely appressed, mostly silvery pubescence on dorsum of mesosoma; pubescence more abundant on head, sides of mesosoma and petiole. Abundant, closely appressed, somewhat medially radiating pubescence over all gastral surfaces, obscuring underlying sculturation; pubescence silvery on venter, rich golden with distinct, dark reddish-brown, median patch on gastral dorsum.

Black with only mandibles very dark reddish brown; condylae medium reddish-brown.

Queen
TL c. 12.20-12.65; HL 2.18- 2.25; HW 1.75-1.68; CI 74-79; SL 2.87-2.91; SI 164- 174; PW 2.70-2.74; MTL 3.83-3.88 (3 measured).

Apart from sexual characters, similar to worker except: pronotal dorsum with humeri narrowly rounded, margins shallowly emarginate posteriorly. Mesoscutum virtually as long as wide; anterior margin evenly rounded; median line distinct, bifurcate anteriorly; parapsides rather flat; mesoscutum flat in lateral view, mesoscutellum convex, distinctly elevated above dorsal plane of mesoscutum. Propodeal and petiolar spines similar to those in worker, but distinctly shorter. Pale golden and silvery, very short, erect hairs on most body surfaces; appressed pubescence very similar to worker with identical patch on gastral dorsum.

Etymology
Derived from the Latin word concilium, meaning assembly, meeting, referring to its close association with P. callima described above.

Determination Clarifications
Polyrhachis cracenta was listed as P. ‘Hagio 03’ by Kohout (2000: 199).