Polyrhachis opacita

This species is evidently restricted to Western Australia, with both known specimens collected on a single occasion at Coral Bay.

Identification
A member of the Polyrhachis gravis species-group. Kohout (2013) - Polyrhachis opacita is characterised by the very finely striate, opaque gaster with the carina on anterior margin of the first gastral tergite only poorly developed.

Key to Polyrhachis gravis species-group workers

Distribution based on Regional Taxon Lists
Australasian Region: Australia.

Castes
Sexuals and immature stages unknown.

Nomenclature

 *  opacita. Polyrhachis (Campomyrma) opacita Kohout, 2013: 102, figs. 4A-B, E-F (w.) AUSTRALIA.

Worker
Dimensions (holotype cited first): TL c. 9.52 ,9.78; HL 2.28, 2.31; HW 1.96, 2.06; 086, 89; SL 2.46, 2.50; SI 125, 121; PW 1.81, 1.81; MTL 3.28, 3.22 (2 measured).

Mandibles with 6 teeth. Clypeal margin widely truncate, truncate portion denticulate medially. Clypeus without distinct median carina; straight in profile with flat base. Frontal triangle distinct. Frontal carinae sinuate with moderately raised margins; central area with rather indistinct frontal furrow. Sides of head in front of eyes weakly convex towards mandibular bases; behind eyes sides narrowly rounding into distinct occipital corners. Eyes convex, in full face view clearly breaking lateral cephalic outline. Ocelli lacking. Pronotal humeri bluntly angular; lateral margins of pronotum converging posteriorly towards moderately impressed promesonotal suture. Mesonotal and propodeal lateral margins converging posteriorly in single, weakly sinuate line; metanotal groove flat. Propodeal dorsum strongly narrowed posteriorly with lateral margins terminating in upturned, somewhat dorsomedially flattened teeth; dorsum curving through narrow gap between closely approximate teeth into steeply descending declivity. Dorsum of petiole armed with a pair of slender spines; outer margins of spines descending into distinctly shorter acute, lateral spines. Gaster in lateral view with anterior face flat; anterior margin of first gastral tergite with poorly indicated carina.

Mandibles finely, longitudinally striate with numerous piliferous pits. Head, including clypeus, reticulate-striate. Pronotal dorsum with rather irregular, somewhat obliquely directed striae; mesonotal dorsum longitudinally striate with sculpture on propodeal dorsum rather irregularly rugose. Sides of mesosoma and petiole finely wrinkled. Gaster very finely and closely reticulate-striate, opaque.

Mandibles with numerous, curved, golden hairs; anterior clypeal margin with numerous, relatively long, reddish-golden setae medially and fringe of shorter setae laterally. Numerous, medium length hairs on clypeus; rather abundant, distinctly shorter, bristle-like hairs on rest of head; distinctly less abundant, short, bristle-like hairs, on dorsum of mesosoma and along lateral margins of petiole. Dorsum of gaster with numerous, short, posteriorly inclined hairs, with hairs distinctly increasing in length towards apex; venter of gaster with numerous, medium to rather long, golden hairs. Closely appressed, greyish or silvery pubescence in various densities on most body surfaces, virtually absent from dorsum of mesosoma.

Whole body, including fore coxae and dorsum of gaster black. Mandibles black, with teeth and bases reddish-brown; narrow band along masticatory borders light reddish-brown. Antennae black with only apical funicular segments light reddish-brown. Femora and middle and hind coxae medium reddish-brown; tarsi black. Venter of gaster and apex reddish-brown.

Etymology
Derived front the Latin opacus, meaning shady, obscure, in reference to its very finely striate, opaque gaster.