Polyrhachis vanachterbergi

Identification
A member of the Polyrhachis vestita species group.

Kohout (2008) - Polyrhachis vanachterbergi is similar in general appearance to the other species of the vestita-group, notably to Polyrhachis cognata and Polyrhachis ogatai. It shares with them the characteristic rusty-red and black pilosity and pubescence. However, it differs by the very short pronotal spines and the shape of the propodeal dorsum that is marginally longer than wide. It also differs from P. ogatai by its smaller size and by the lack of the peculiar antennal process in the latter species (see Kohout, 2008).

Distribution based on Regional Taxon Lists
Indo-Australian Region: Indonesia, Sulawesi.

Nomenclature

 *  vanachterbergi. Polyrhachis vanachterbergi Kohout, 2008b: 298, figs. 1-3 (w.) INDONESIA (Sulawesi).

Worker
(holotype cited first): TL c. 13.30, 12.85-14.51; HL 3.17, 3.07-3.33; HW 2.27, 2.24-2.37; CI 72, 69-73; SL 4.38, 4.33-4.59; SI 193, 187-200; PW 1.81, 1.66-1.91; MTL 5.24, 5.24-5.59 (13 measured).

Anterior clypeal margin arcuate, obtusely and widely truncate medially. Clypeus with blunt median carina that is more prominent posteriorly. Clypeus in profile straight for most of its length, posteriorly rounding into moderately impressed basal margin that is laterally indicated by a flat, thin line. Frontal triangle distinct. Frontal carinae with sharp, highly elevated laminate lobes; central area concave with rather flat frontal furrow. Sides of head in front of eyes weakly convex; behind eyes sides rounding into convex, medially weakly emarginate, occipital margin. Eyes convex, in full-face view only marginally breaking lateral cephalic outline. Ocelli lacking. Pronotal dorsum weakly convex, with pair of very short, anteriorly directed, dorso-medially and ventrally flattened, horizontal spines; promesonotal suture deeply impressed laterally, medially indicated by shallow, bowed line. Mesonotal dorsum flat, with weakly upturned, anteriorly and posteriorly rounded, lateral margins; metanotal groove well impressed. Propodeum with lateral margins subparallel, anteriorly forming distinctly upturned laminae; margins rather flat posteriorly, terminating in upturned teeth; propodeal dorsum and declivity almost in the same plane, forming only weakly angled line in lateral view (fig. 2). Petiole in profile with anterior and posterior faces flat, converging dorsally; petiolar dorsum acute, transversely arcuate, terminating laterally in weakly upturned denticles. Anterior face of first gastral segment flat basally, with anterodorsal margin widely rounding onto dorsum of gaster.

Mandibles distinctly, longitudinally striate with numerous piliferous pits. Head, mesosoma, petiole and gaster generally very finely reticulate-punctate with sculpturation on pronotal and mesonotal dorsa somewhat organised into irregular, rather indistinct, longitudinal striae.

Mandibles with numerous, semi-erect, golden hairs (= setae). Anterior clypeal margin fringed medially with medium length, anteriorly directed, golden setae, reducing in length laterally. Leading edge of antennal scape with short, erect, yellowish-brown hairs and few hairs arising along inferior edge distally. Front and sides of head with medium length, erect, mostly rusty-brown hairs, those on vertex distinctly longer, darker and more anteriorly directed. Mesosomal dorsum, except declivity, with numerous, relatively long, anteriorly curved, rusty-brown or black hairs, those on sides of mesosoma distinctly shorter. Coxae with several long, yellowish- and rusty-brown hairs. Legs with abundant, black and rusty-brown hairs, notably on tibiae, basal segments of tarsi and ventral surfaces of femora. Dorsal surfaces of fore femora hairless; middle and hind femora with only a few, short hairs along dorsal surfaces. Petiole with several short, black hairs near dorsal margin in lateral view. Gaster with abundant, relatively long, somewhat posteriorly directed, black and brown hairs. Very short, dense, adpressed, rusty-red pubescence over most body surfaces, notably over anterior portion of pronotal dorsum; somewhat yellowish pubescence on pronotal collar and meso- and metapleurae.

Black throughout, with legs very dark reddish-brown in some specimens.

Type Material
Holotype: “Indonesia, C. Sulawesi, nr Luwuk, Salodik, c. 400 m, 21-31.x.1989, Malaise trap 14, C. van Achterberg, RMNH’89” (worker). Paratypes: data as for holotype (17 workers). Type distribution: Holotype and most paratypes in ; 2 paratypes in ; 1 paratype each in, and.

Etymology
Named aft er the collector, Prof. Dr Ing. C. (Kees) van Achterberg, whose collecting across Indonesia and elsewhere in South East Asia has brought to light a number of new species of ants and other insects.