Polyrhachis noonananti

Identification
Polyrhachis noonannanti is very similar to other species of the aculeata-complex (e.g. Polyrhachis cybele and Polyrhachis hemiopticoides); however, it is easily separable by the unique structure of the front of the head (i.e. a short median carina running from the frontal triangle to the central area between the anteriorly flat frontal carinae), the presence of a shallow posterior depression in the profile of the mesosoma and the greatly reduced petiolar spines.

Distribution based on Regional Taxon Lists
Oriental Region: Thailand.

Nomenclature

 *  noonananti. Polyrhachis (Myrma) noonananti Kohout, 2013: 150, figs. 12, 17-18 (w.) THAILAND.

Description
Description. Worker. Dimensions (holotype): TL c. 5.74; HL 1.43; HW 1.22; CI 85; SL 1.87; SI 153; PW 0.97; MTL 1.93.

Anterior clypeal margin arcuate, widely medially truncate. Clypeus with median carina blunt anteriorly, weakly raised towards almost flat basal margin; straight in profile. Frontal triangle distinct; short median carina running for short distance from triangle towards central area. Frontal carinae closely approximate and rather flat anteriorly, distinctly raised and sinuate from midlength with central area relatively wide posteriorly. Sides of head in front of eyes converging towards mandibular bases in weakly convex line; behind eyes sides widely rounding into occipital margin. Eyes convex, only moderately posteriorly truncate. Ocelli lacking. Dorsum of mesosoma convex longitudinally and transversely, with rather poorly developed lateral margins and in profile with a very shallow depression indicating position of metanotal groove. Pronotal spines relatively short, about 1.5x longer than their basal width; lateral margins of pronotal dorsum subparallel, gently rounding into weakly impressed promesonotal suture. Mesonotal dorsum with lateral margins flat, weakly converging posteriorly; metanotal groove only weakly impressed dorsally. Propodeal dorsum with lateral margins converging posteriorly and terminating in narrowly rounded, weakly raised ridges that continue medially and merge into a dorsally bowed carina dividing propodeal dorsum from shallowly concave declivity; secondary carinae extending from propodeal margins towards propodeal spiracles, dividing declivity from sides of propodeum. Petiole biconvex in profile, armed with a pair of very short, acute spines situated on dorsolateral angles of petiole; rather blunt, secondary tooth situated laterally at base of each spine. Anterior face of first gastral segment in unique holotype is damaged beyond recognition of its shape or height (Figs 17, 18).

Mandibles finely, longitudinally striate with numerous piliferous pits. All dorsal body surfaces very smooth and highly polished. Sides of mesosoma very finely wrinkled.

Mandibles along masticatory borders and near bases with a few semierect, relatively short, golden hairs. Anterior clypeal margin with a few moderately long, anteriorly directed, golden setae medially. A few pairs of moderately long, erect, golden hairs on clypeus and along frontal carinae. Hairs totally absent from dorsum of mesosoma, petiole, dorsum of first gastral segment, femora and tibiae. Only a few short hairs along superior edge of antennal scapes; longer hairs on anterior and posterior faces of fore coxae. Gaster with numerous, posteriorly directed hairs around apex and on gastral venter.

Colour. Body black; mandibular teeth, antennae, tarsi and venter of gaster very dark reddish brown. Trochanters, femora and tibiae, except joints, distinctly light reddish brown.

Sexuals and immature stages unknown.

Etymology. Named after Dr Nawee Noon-anant of Prince of Songkla University, Hat Yai, Thailand, in appreciation of his support during my visit to southern Thailand and for making the Polyrhachis material in his collection available for examination.