Proceratium hirsutum

The type material was collected in a rainforest.

Identification
A Proceratium species belonging to the silaceum clade and differing from all the species of this clade by the following combination of worker characters: body with very long hairs, area between basal and declivous propodeal faces subangulate, frontal carinae far from each other, petiolar node thick, and SI ≥ 74.

Proceratium hirsutum, with a ST ≥ 74, exhibits the second highest SI value within the silaceum clade, surpassed only by Proceratium relictum (SI 77.7). hirsutum differs from relictum mainly in the shape of the petiole, dorsally convex instead of flattened, but it shares with relictum the hind basitarsi only slightly shorter than hind tibiae. hirsutum shares with Proceratium banjaranense the abundant long hairs, but it differs from banjaranense by the more superficial sculpture, larger frontal carinae and longer scapes. hirsutum, moreover, shares with gigas the broad, diverging frontal carinae, but hirsutum has denser and longer hairs and a more superficial integumental sculpture. (Baroni Urbani and de Andrade 2003)

Distribution based on Regional Taxon Lists
Australasian Region: Australia.

Nomenclature

 *  hirsutum. Proceratium hirsutum De Andrade, in Baroni Urbani & De Andrade, 2003b: 338, fig. 135 (w.) AUSTRALIA.

Worker
Head slightly longer than broad and with the sides gently diverging backwards. Vertex in full face view convex. Clypeus reduced and slightly longer than the antennal sockets. Anterior border of the clypeus truncate. Frontal carinae far from each other, not covering the antennal insertions. Lateral expansions of the frontal carinae very broad, little raised, diverging on the two anterior fourths, converging on the third fourth, slightly diverging and carinate only on the last fourth. Frontal area gently concave in the middle and with a central, thick, longitudinal carina starting from the last fourth and prolonging posteriorly. Head anterolaterally with a short, thin, longitudinal carina. Genal carinae marked, each carina corresponding to the external border of a sulcus. Eyes represented by a minute, dark dot below the integument and on the middle of the head sides. First funicular joint about 1/3 longer than broad. Funicular joints 2-10 slightly broader than long. Last funicular joint about 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 denticles before the pointed apical tooth. Palp formula 2,2.

Mesosoma convex and about as long as the maximum head length (mandibles included) in profile. Pronotal and propodeal sutures absent. Basal face of the propodeum declivous posteriorly. Declivous face of the propodeum gently sloping posteriorly. Area between basal and declivous faces of the propodeum weakly concave medially and subangulate on each side. Sides of the declivous face superficially carinate. Propodeal spiracle round and above mid height in lateral view.

Petiole subrectangular and narrow, its anterior border straight and anterolaterally narrowly carinate. Ventral process of the petiole triangular. Postpetiole in dorsal view with convex sides. Postpetiolar sternite anteromedially with a marked transversal carina interrupted medially, gently convex posteriorly in side view. Constriction between postpetiole and gaster impressed. Gastral tergite I about 2/5 longer than the postpetiole and convex on the curvature. Remaining gastral tergites and sternites curved ventrally.

Legs 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 1/8 or 1/9 shorter than hind tibiae. Second tarsomere of hind legs about as long as the pretarsus. Pretarsal claws simple. Arolia absent.

Sculpture. Head minutely rugosopunctate. Sides of the head with additional, small reticulation. Mesosoma, petiole and postpetiole with minute punctation-granulation. Gaster and legs with minute piligerous punctures. Body covered by hairs of three main types: (1) short, dense, subdecumbent on the whole body, suberect and sparse on the funicular joints; (2) long, erect or suberect on the whole body, slightly shorter on the antennal 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. Yellow-light brown.

Measurements in mm and Indices: TL 3.35-3.62; HL 0.75-0.81; HW 0.69-0.76; EL -0.05; SL 0.56-0.60; WL 0.96-1.06; PeL 0.25-0.27; PeW 0.35-0.37; HFeL 0.62-0.68; HTiL 0.49-0.54; HBaL 0.43-0.49; LS4 0.36-0.39; LT4 0.74-0.78; CI 92.0-93.8; SI 74.1-74.7; IGR 0.48-0.50.

Etymology
From the Latin hirsutus (= hairy) referred to the dense, long hairs of this species.