Proceratium robustum

The type specimens were collected in rainforest.

Identification
A member of the silaceum clade and resembling Proceratium gracile but differing from it, in the worker, by the following characters: hind tarsomere shorter, CI > 94 instead of < 93, SI < 65 instead of ≥ 69 and hairs of type (2) longer and denser.

Distribution
Australia: New South Wales.

Distribution based on Regional Taxon Lists
Australasian Region: Australia.

Nomenclature

 *  robustum. Proceratium robustum De Andrade, in Baroni Urbani & De Andrade, 2003b: 356, fig. 140 (w.q.) AUSTRALIA.

Holotype worker from New South Wales, Australia, labeled: "NSW. Dorigo N. P., Glade, 2700 ft., rainforest,12.ii.1968, R. W. Taylor, ex rotting log, ", in ANIC; 3 paratype workers, same data and collection as the holotype.

Type Material


The isolated gyne attributed to Proceratium robustum, besides coming from the same area as the workers, shares with the workers the integumental sculpture and the hairs of type 2 decumbent or appressed on the petiole and gaster, instead of suberect as in the majority of the Proceratium species. The thick tarsi of both castes also strongly support this attribution.

Worker
Head almost as long as broad, with gently convex sides. Vertex in full face view weakly convex. Clypeus reduced and as long as the antennal sockets. Anterior border of the clypeus truncate. Frontal carinae broad and badly covering the antennal insertions. Lateral expansions of the frontal carinae broad, raised, diverging on the two anterior thirds, converging and carinate only on the posterior third. Frontal area concave and with a longitudinal carina prolonging posteriorly. Head anterolaterally with a short, longitudinal carina. Genal carinae marked, each carina corresponding to the external border of a sulcus. Eyes visible as a dark dot below the integument, small and placed 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 8-9 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 declivous posteriorly. Area between the basal and declivous faces of the propodeum dorsally gently concave, the concavity superficially carinate, the carina ending on each side in an angle. 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 anterolaterally weakly carinate. Ventral process of the petiole large, subtriangular and pointed posteriorly. Postpetiole slightly shorter than 1/3 of the gastral tergite I, with convex sides in dorsal view. Postpetiolar sternite anteromedially with a marked subtriangular projection, gently convex posteriorly in side view. 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 1/4 shorter than hind tibiae. Second tarsomere of hind legs slightly shorter than pretarsus. Pretarsal claws simple. Arolia absent.

Sculpture. Head reticulate-punctate and rugulose, the rugosities more longitudinal on the sides. Mesosoma punctate and with short, transversal rugosities on the middle of the mesonotum and of the propodeum. Petiole punctate, the punctures approaching granulation. Postpetiole, gaster and legs shining and with minute piligerous punctures.

Body covered by hairs of three main types: (1) short, dense, suberect or subdecumbent on the whole body, slightly longer on the postpetiole and gaster, sparser and erect on the funicular joints; (2) longer than type (1), sparse, subdecumbent on the head and mesosoma, decumbent or appressed on the petiole and postpetiole, subdecumbent or decumbent, denser on the gaster, absent on the antennae; (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, and the scapes with sparse hairs similar to type (2).

Colour. Light brown with slightly lighter scapes and legs.

Measurements in mm and Indices: TL 3.12-3.19; HL 0.72; HW 0.69-0.70; EL 0.04-0.05; SL 0.45-0.46; WL 0.88; PeL 0.22-0.23; PeW 0.31-0.32; HFeL 0.52-0.53; HTiL 0.42-0.46; HBaL 0.29-0.30; LS4 0.35-0.36; LT4 0.70; CI 95.8-97.2; SI 62.5-63.8; IGR 0.48-0.51.

Queen
(tentative attribution). Differing from the worker in the following details: eyes large, about 1/3 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 gently convex and with the posterior border subtruncate. Dorsum of the scutellum with a longitirdinal carina prolonging to the posterior half of the mesonotum. Metanotum with a small pointed tooth. Basal face of the propodeum medially slightly more concave and laterally denticulate.

Posterior half of the mesonotum and scutellum with irregular, longitudinal rugosities.

Measurements in mm and Indices: TL 3.48; HL 0.72; HW 0.70; EL 0.23; SL 0.46; WL 1.06; PeL 0.25; PeW 0.35; HFeL 0.59; HTiL 0.46; HBaL 0.35; LS4 0.38; LT4 0.79; CI 97.2; SI 63.8; IGR 0.48.

Etymology
From the Latin robustus (= robust, sturdy), referred to stout body of this species.

References based on Global Ant Biodiversity Informatics

 * Baroni Urbani C., and M.L de Andrade. 2003. The ant genus Proceratium in the extant and fossil record (Hymenoptera: Formicidae). Museo Regionale di Scienze Naturali, Monografie 36: 1-480.