Proceratium austronesicum

Identification
A member of the silaceum clade. Resembling Proceratium dayak (from Sarawak) with which it shares the narrow frontal carinae, but differing from it, in the worker, by the smoother integument and by the shorter hind basitarsi. It differs from the three other Papuan species of Proceratium, Proceratium ivimka, Proceratium snellingi and Proceratium papuanum mainly by its larger size TL ≥ 2.70 mm instead of < 2.60 mm.

Distribution
Widespread in Papua New Guinea.

This taxon was described from New Guinea.

Nomenclature

 *  austronesicum. Proceratium austronesicum De Andrade, in Baroni Urbani & De Andrade, 2003b: 313, fig. 128 (w.Q.) NEW GUINEA.

Worker
Head about as broad as long and with the sides gently diverging posteriorly. Vertex in full face view almost straight. Clypeus reduced and as long as the antennal sockets. Anterior border of the clypeus truncate. Frontal carinae not very broad and not covering the antennal insertions. Lateral expansions of the frontal carinae narrow, weakly raised, diverging on the two anterior fourths, converging on the third fourth, parallel and carinate only on the last fourth. Frontal area gently concave and with a superficial, thin, longitudinal carina prolonging posteriorly. Head anterolaterally with a short, longitudinal carina. Genal carinae marked, each carina corresponding to the external border of a deep sulcus. Eyes visible as a dark dot below the integument, small and on the middle of the head sides. First funicular joint about as broad as long. Funicular joints 2-10 broader than long. Last funicular joint as long as the sum of joints 6-10. Scapes short of the vertexal margin and gently thickening apically. Masticatory margin of the mandibles with 8 denticles before the pointed apical tooth. Palp formula 2,2.

Mesosoma in side view gently convex, slightly shorter or about as long as the maximum head length (mandibles included). Pronotal and propodeal sutures absent. Basal face of the propodeum declivous posteriorly. Area between the basal and declivous faces of the propodeum gently concave and with a triangular denticle on each side. Declivous face of the propodeum sloping posteriorly. Sides of the declivous face of the propodeum carinate. Propodeal spiracle round and above mid height in lateral view.

Petiole subrectangular and not very thick. Anterior border of the petiole straight and anterolaterally carinate. Ventral process of the petiole large, triangular and slightly pointed posteriorly. Postpetiole about 1/3 shorter than gastral tergite 1. Postpetiole in dorsal view with convex sides. Postpetiolar sternite anteromedially with a marked subtriangular projection. Postpetiolar sternite in side view gently convex posteriorly. Constriction between postpetiole and gaster impressed. Gastral tergite I strongly convex on the curvature. Remaining gastral tergites and sternites curved ventrally.

Legs not very elongate. All tibiae with a pectinate spur. Spurs of fore legs without basal spine. Fore basitarsi longer than the mid ones. Hind basitarsi about 1/4 shorter than hind tibiae. Second tarsomere of hind legs shorter than pretarsus. Pretarsal claws simple. Arolia absent.

Sculpture. Body largely shining. Head, mesosoma, petiole, postpetiole and gaster covered by small piligerous punctures, the punctures denser on the head, very sparse on the center of the first gastral tergite. Area below the eyes and ventral part of the head reticulorugose. Legs minutely punctate. Body covered by hairs of three main types: (1) short, dense, suberect or subdecumbent on the whole body, suberect and sparse on the funicular joints; (2) longer than type (1), erect on the whole body, sparse and slightly shorter on the scapes, absent on the funiculi; (3) shorter than hair type (1), dense and decumbent on the funicular joints only. In addition the funicular joints bear whitish, thick, appressed, sparse hairs.

Colour. Dark brown-black with lighter anterior third of the head, antennae and legs.

Measurements in mm and Indices: TL 2.70-3.15; HL 0.63-0.70; HW 0.61-0.69; EL 0.03-0.05; SL 0.41-0.46; WL 0.76-0.90; PeL 0.18-0.22; PeW 0.29-0.33; HFeL 0.46-0.52; HTiL 0.39-0.44; HBaL 0.28-0.35; LS4 0.28-0.35; LT4 0.58-0.70; CI 96.8-98.6; SI 64.1-65.7; IGR 0.48-0.51.

Queen
Differing from the worker in the following details: eyes very large, about 1/4 of the head length, composed by many facets and with ocular pilosity. Ocelli well developed. Mesosoma robust and convex in side view. Parapsidal furrows marked. Scutellum with the sides converging posteriorly, with the posterior border round and dorsally with a median carina. Metanotum with a minute denticle.

Fore wings of our type 4, hind wings of our type 3 as defined in the description of the genus.

Measurements in mm and Indices: TL 3.30; HL 0.68; HW 0.67; EL 0.20; SL 0.46; WL 0.97; PeL 0.22; PeW 0.34; HFeL 0.54; HTiL 0.44; HBaL 0.34; LS4 0.37; LT4 0.74; CI 98.5; SI 67.6; IGR 0.50.

Type Material
Holotype worker from Papua New Guinea labelled: "PNG: Morobe, Wau, Mt. Kaindi, 25.V.92, 1800 m, G. Cuccodoro", in.

Etymology
"Austronesicum" is a neologism created by analogy with the common name of most indigenous languages spoken in Papua.