Polyrhachis incerta

The nest of P. incerta is unknown, but the foraging habits of the species suggest it is ground-nesting like other, closely related species.

Identification
A member of the Polyrhachis micans species-group.

Kohout (2008) - P. incerta is closely allied to both Polyrhachis micans and Polyrhachis ops; however, all three species are easily distinguished from each other and from another group of very similar species that includes Polyrhachis schwiedlandi and several other, mostly undescribed species. Besides their relatively large size, all these species share a broadly truncate anterior clypeal margin, eyes situated close to the occipital comers of the head and a scale like petiole. In species related to P. micans, the petiole is armed with a pair of dorsal, often elongated, acute spines and a pair of usually shorter lateral spines or teeth that may be reduced to blunt angles. In contrast, in species related to P. schwiedlandi, the dorsum of petiole is arcuate with a shallow median emargination and a pair of very short lateral spines. However, in several newly discovered species the petiolar dorsum bears a pair of rather distinct teeth and a pair of short, acute, dorsa-posteriorly curved lateral spines, an arrangement not unlike that found in those species related to P. micans

The two disjunct occurrences of this species exhibit very similar morphology, but differ distinctly in colour pattern. Specimens from the Northern Territory are more-or-less uniformly reddish-brown, while those from Queensland are distinctly bicoloured, with the sides of head, vertex and most of the mesosoma, except the propodeal declivity, black or very dark reddish-brown.

Polyrhachis incerta can be distinguished from P. micans, P. ops and other closely related species using the "Key to select Polyrhachis (Campomyrma) of Australian" (see link below).

Distribution based on Regional Taxon Lists
Australasian Region: Australia.

Biology
Polyrhachis incerta appears to be a very rare species currently known from two widely separated regions. The type series specimens were collected in Kakadu National Park in the Northern Territory, with additional specimens collected on Groote Eylandt. The only specimens recorded from Queensland were collected on a single occasion by F.P. Dodd at Townsville in 1902.

Castes
Sexuals and immature stages unknown.

Nomenclature

 *  incerta. Polyrhachis incerta Kohout, 2008c: 163, figs. 1, 3, 4 (w.) AUSTRALIA.

Worker
(holotype cited first): TL c. 7.96, 7.56-8.32; HL 2.00, 1.87-2.03; HW 1.81, 1.68-1.84; CI 90, 87-92; SL 2.09, 2.00-2.15; SI 115, 115-123; PW 1.47, 1.34-1.50; MTL 2.43, 2.28-2.50 (9 measured).

Mandibles with 5 teeth reducing in length towards base. Anterior clypeal margin widely medially truncate; truncate portion with irregularly, obtusely denticulate corners. Clypeus with blunt, poorly defined median carina; almost straight in profile with shallowly impressed basal margin. Frontal carinae sinuate with moderately raised margins; central area concave with poorly indicated frontal furrow. Sides of head in front of eyes weakly convex, only marginally narrowed towards mandibular bases; behind eyes sides forming rather distinct, narrowly rounded, occipital corners. Eyes moderately convex, in full face view breaking lateral cephalic outline. Ocelli lacking. Pronotal dorsum distinctly wider than long; humeri bluntly angular with margins converging anteriorly towards pronotal collar; lateral pronotal margins subparallel, posteriorly rounding into well impressed, anteriorly bowed promesonotal suture. Mesonotal dorsum with lateral margins converging posteriorly in weakly convex line; metanotal groove poorly indicated. Propodeal margins weakly converging posteriorly, or virtually subparallel in some specimens, terminating in short, upturned, somewhat dorsally flattened, acute teeth; their inner margins continuous for some distance but failing to meet medially; propodeal dorsum curving into steeply oblique declivity in medially uninterrupted line. Petiole scale-like, slender and more-or-less triangular in lateral view; dorsum armed with a pair of slender, medium length, weakly diverging, acute spines; inner margins of spines contiguous medially, forming rather narrow, U-shaped dorsum of petiole; outer margins of spines descending into distinct, dentate angles. Anterior face of first gastral segment flat, marginally higher than full height of petiole, narrowly rounding onto dorsum of gaster.

Head, mesosoma and dorsum of gaster densely and finely reticulate-punctate, with sculpturation on vertex, sides of head and dorsum of mesosoma somewhat organised into weak, irregular, longitudinal striae, with those on mesonotal dorsum diverging posteriorly towards lateral margins of segment. Sides of mesosoma and petiole finely wrinkled. Sides and venter of gaster shagreened.

Mandibles with numerous curved, golden hairs. Anterior clypeal margin medially with several, anteriorly directed, unequal length golden setae and shorter setae fringing margin laterally. A single pair of very· short, erect hairs near basal clypeal margin and several hairs on posterior face of fore coxae. Gaster with medium length, mostly posteriorly inclined, golden hairs around apex and along posterior margins of sternites. Very short, closely appressed pubescence in various densities over most dorsal body surfaces and gastral venter.

Distinctly light to medium reddish-brown, with only mandibular teeth, anterior clypeal margin, frontal carinae, pronotal and mesopleural margins, propodeal and lateral petiolar teeth very narrowly bordered with black. Vertex, dorsum of mesosoma along promesosonotal suture and sides of mesosoma a shade darker in some specimens.

Determination Clarifications
Listed as P. 'Campo 01' by Kohout (2000: 190).