Proceratium gracile

Identification
A Proceratium species belonging to the silaceum clade and resembling Proceratium robustum but differing from it, in the worker, by the following characters: hind tarsomeres longer, CI < 93 (instead of > 94), SI ≥ 69 (instead of < 65) and the by the hairs of type (2) shorter and sparser.

Distribution based on Regional Taxon Lists
Australasian Region: Australia.

Nomenclature

 *  gracile. Proceratium gracile De Andrade, in Baroni Urbani & De Andrade, 2003b: 353, fig. 139 (w.) AUSTRALIA.

Worker
Head slightly longer than broad and with subparallel sides. Vertex in full face view gently convex. Clypeus reduced and as long as the antennal sockets. Anterior border of the clypeus truncate. Frontal carinae broad and partly covering the antennal insertions. Lateral expansions of the frontal carinae broad, raised, diverging on the two anterior fourths, converging on the third fourth, diverging and carinate only on the posterior fourth. Frontal area concave and with a longitudinal carina prolonging posteriorly. Head anterolaterally with a short, longitudinal carina. Genal carinae superficially marked, each carina corresponding to the external border of a superficial sulcus. Eyes absent. 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 5-6 denticles before the pointed apical tooth. Palp formula 2,2.

Mesosoma gently convex and slightly shorter than maximum head length (mandibles included) in profile. Pronotal and propodeal sutures absent. Basal face of the propodeum gently declivous posteriorly. Area between the basal and declivous faces of the propodeum with a dorsal, faint, transversal carina. Each side between the basal and declivous faces of the propodeum subangulate. Declivous face of the propodeum flat. Sides of the declivous face of the propodeum slightly marginate. Propodeal spiracle round and above mid height in lateral view.

Petiole subrectangular and not very thick. Anterior border of the petiole straight and weakly carinate anterolaterally. Ventral process of the petiole large, subtriangular and pointed posteriorly. Postpetiole about 1/4 shorter than gastral tergite I. Postpetiole in dorsal view with convex sides. Postpetiolar sternite anteromedially with a marked subtriangular projection, gently convex posteriorly in profile. Constriction between postpetiole and gaster impressed. Gastral tergile I convex on the curvature, strongly convex after the postpetiolar constriction in dorsal view. 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 1/6 shorter than hind tibiae. Second tarsomere of hind legs shorter than pretarsus. Pretarsal claws simple. Arolia absent.

Sculpture. Head reticulate-punctate rugulose. Mesosoma, petiole, postpetiole, gaster and legs superficially shining, minutely punctate to weakly granulate, the granulation less marked on the gaster.

Body covered by hairs of three main types: (1) short, dense, suberect or subdecumbent on the whole body, slightly longer on the gaster, sparser and erect on the funicular joints; (2) longer than type (1), erect and relatively sparse on the whole body, 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. Light ferrugineous-brown with slightly lighter legs.

Measurements in mm and Indices: TL 2.98-3.27; HL 0.71-0.74; HW 0.65-0.68; EL absent; SL 0.49-0.52; WL 0.85-0.90; PeL 0.21-0.22; PeW 0.32-0.35; HFeL 0.52-0.56; HTiL 0.43-0.46; HBaL 0.36-0.40; LS4 0.30-0.35; LT4 0.61-0.72; CI 91.5-91.9; SI 69.0-70.1; IGR 0.48-0.49.

Type Material
Holotype worker from Queensland, Australia labelled: "QLD. Mt. Cordeaux, Gunning Hams Gap, 3000', 1.V.1962, R. W. Taylor, rtn. wood forest floor, rainforest, R. W. Taylor, Acession 722, Ants Vials 35-131", in ANIC, 5 paratypc workers, same data and collector as the Holotype.

Etymology
From the Latin gracilis (= weak) as opposed to the species Proceratium robustum.