Proceratium oceanicum

The type material was collected in a rainforest, on soil under grass.

Identification
A member of the silaceum clade.  Proceratium oceanicum shares with Proceratium relictum the squamiform petiole dorsally flattened. Few other species have a weakly squamiform petiole but, in this case, it is dorsally much less flattened than in relictum and oceanicum. Differing from relictum, in the worker, by the smaller size (TL < 3.7 mm instead of > 5.0 mm) and by the SI 76.

Key to Oceanian Proceratium Species

Distribution based on Regional Taxon Lists
Indo-Australian Region: Fiji.

Nomenclature

 *  oceanicum. Proceratium oceanicum De Andrade, in Baroni Urbani & De Andrade, 2003b: 310, fig. 127 (w.) FIJI IS.

Worker
Head slightly longer than broad and with the sides gently diverging posteriorly. Vertex in full face view gently convex. Clypeus reduced and as long as the antennal sockets. Anterior border of the clypeus truncate. Frontal carinae closer to each other than in relictum, not covering the antennal insertions. Lateral expansions of the frontal carinae narrower than in relictum, weakly raised, diverging on the two anterior thirds, parallel and lower on the posterior third. Frontal area flat and with a superficial, thin longitudinal cariila. Head anterolaterally with a short, longitudir~al 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 1/4 longer than broad. Funicular joints 2-10 broader than long. Last funicular joint as long as the sum of joints 7-10. Scapes short of the vertexal margin and gently thickening apically. Masticatory margin of the mandibles with 5 denticles before the pointed apical tooth. Palp formula 2,2.

Mesosoma in profile convex and about as long as the maximum head length (mandibles included). Pronotal and propodeal sutures absent. Basal face of the propodeum gently declivous posteriorly. Declivous face of the propodeum sloping posteriorly. Each side of the declivous face of the propodeum not carinate and with a trace of a minute, broad angle. Propodeal spiracle round and above mid height in lateral view.

Petiole squamiform, compressed and weakly carinate dorsally. Anterior border of the petiole straight, without neck and carina. Ventral process of the petiole small, stout and triangular. Postpetiole anteriorly slightly protruding over the petiole; its sides diverging and gently convex posteriorly. Postpetiolar sternite anteromedially with a marked subtriangular projection. Postpetiolar sternite gently convex posteriorly in profile. Constriction between postpetiole and gaster impressed. Gastral tergite I about 1/3 longer than the postpetiole and slightly convex on the curvature. Remaining gastral tergites and sternites curved ventrally.

Legs slender and slightly 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. Body more shining than in relictum. Head covered with small piligerous punctures, the punctures denser, larger and mixed with irregular rugosities anterolaterally. Mesosoma, petiole postpetiole, gaster and legs covered by piligerous punctures smaller and sparser than on the posterior part of the head. Lower meso- and metapleurae with variably impressed, irregular, thin rugosities.

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 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 with lighter anterior half of the head. Legs dark orange to brown.

Measurements in mm and Indices: TL 3.47-3.59; HL 0.78-0.80; HW 0.75-0.78; EL 0.03-0.04; SL 0.54-0.56; WL 0.98-1.00; PeL 0.23-0.24; PeW 0.43-0.47; HFeL 0.63-0.65; HTiL 0.50-0.51; HBaL 0.39; LS4 0.39-0.40; LT4 0.76-0.80; CI 94.9-97.5; SI 68.3-71.8; IGR 0.50-0.52.

Type Material
Holotype worker from Fiji Islands labelled: "Nadarivatu, Viti, Fiji, R. W. Taylor, 16.II.1962, on soil under grass, Rainforest, R. W. Taylor, acc 25", in.

Etymology
Oceanicus is a neologism created to indicate the provenance from Oceania.