Proceratium dayak

Identification
A Proceratium species belonging to the silaceum clade, resembling Proceratium austronesicum, but differing from it, in the worker, by the body with denser and stronger punctures, longer hind basitarsi, and narrower frontal carinae. (Baroni Urbani and de Andrade 2003)

Distribution
This taxon was described, and is only known, from (Sarawak) Borneo.

Nomenclature

 *  dayak. Proceratium dayak De Andrade, in Baroni Urbani & De Andrade, 2003b: 317, fig. 129 (w.) BORNEO.

Worker
Head slightly longer than broad 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, narrower than in austronesicum 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, subparallel 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 absent. First funicular joint slightly longer than broad. 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 6-7 denticles before the pointed apical tooth. Palp formula 2,2.

Mesosoma in side view gently convex, 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 small triangular tooth 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. Anterior border of the petiole straight and anterolaterally carinate. Ventral process of the petiole large, triangular. Postpetiole about 1/3 shorter than gastral tergite I. Postpetiole in dorsal view with its sides diverging anteriorly and convex posteriorly. Postpetiolar sternite anteromedially with a marked subtriangular projection, gently convex posteriorly in profile. Constriction between postpetiole and gaster impressed. Gastral tergite I 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 1/5 shorter than hind tibiae. Second tarsomere of hind legs shorter than pretarsus. Pretarsal claws simple. Arolia absent.

Sculpture. Head, mesosoma, petiole and postpetiole densely punctate, the punctures larger on the dorsum of the mesosoma, of the petiole and of the postpetiole. Areas below the eyes and ventral part of the head reticulorugose. Basal face of the propodeum with additional, thin, irregular rugulae. Gaster and 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) long and erect, but shorter than in austroncsicum, on the whole body, sparser 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 ferrugineous with slightly lighter legs.

Measurements in mm and Indices: TL 2.90; HL 0.68; HW 0.65; EL absent; SL 0.44; WL 0.83; PeL 0.21; Pew 0.32; HFeL 0.49; HTiL 0.39; HBaL 0.32; LS4 0.31; LT4 0.63; CI 95.6; SI 64.7; IGR 0.49.

Type Material
Holotype worker from Sarawak labeled: "Sarawak, 4th Divis. G. Mulu Expd. X.1977, Camp 5, H. Vallack, soil core", in.

Etymology
Dayak is the name of one of the populations of Borneo. It is used as a name in apposition.