Proceratium pumilio

The types were collected in rainforest.

Identification
A member of the silaceum clade, resembling Proceratium australe and Proceratium caledonicum but differing from australe, in the worker, by the narrower frontal carinae, and from caledonicum, in the worker, by the body with stronger sculpture and by the erect hairs shorter, and from both species, by the broader petiole and by the mesosoma more convex in profile.

Distribution based on Regional Taxon Lists
Australasian Region: Australia.

Nomenclature

 *  pumilio. Proceratium pumilio De Andrade, in Baroni Urbani & De Andrade, 2003b: 350, fig. 138 (w.) AUSTRALIA.

Worker
Head slightly longer than broad and with the sides wealtly diverging posteriorly. Vertex in full face view convex and gently incised medially. Clypeus reduced and as long as the antennal sockets. Anterior border of the clypeus truncate. Frontal carinae not very far from each other, slightly covering the antennal insertions. Lateral expansions of the frontal carinae narrow, little raised, gently diverging on the two anterior thirds, shortly converging, subparallel and carinate only on the last third. Frontal area gently concave and with a central longitudinal carina starting from the posterior border of the concavity and prolonging posteriorly. Head anterolaterally with a short longitudinal carina. Genal carinae marked, each carina corresponding to the external border of a deep sulcus. Eyes composed by a small agglomeration of ommatidia and on the middle of the head sides. First funicular joint about as long as 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 5 denticles before the pointed apical tooth. Palp formula 2,2.

Mesosoma convex and slightly shorter than maximum head length (mandibles inc1uded)in profile. Pronotal and propodeal sutures absent. Basal face of the propodeum gently declivous posteriorly. Declivous face of the propodeum sloping posteriorly. Area between the basal and declivous faces of the propodeum weakly concave medially and with a minute, carinate denticle on each side. Declivous face superficially marginate laterally. Propodeal spiracle round and above mid height in lateral view.

Petiole subrectangular and nanow. Petiolar width more than 1 and ½ broader than long. Anterior border of the petiole straight and anterolaterally weakly carinate. Ventral process of the petiole small and triangular. Postpetiolar sternite anteromedially with a marked subround projection, gently convex in side view. Constriction between postpetiole and gaster impressed. Gastral tergite I about 1/3 longer than the postpetiole and convex on the curvature. Remaining gastral tergites and sternites curved ventrally.

Legs moderately short. 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 about as long as the pretarsus. Pretarsal claws simple. Arolia absent.

Sculpture. Head dorsum, mesosoma, petiole and postpetiole punctate, the punctures denser and more impressed on the head, very superficial and resembling minute foveae on the mesosoma. Head sides with dense, small, piligerous foveae resembling reticulation and few, slightly longitudinal rugosities. Gaster smooth and with minute piligerous punctures, the punctures denser and larger on the sides. Legs punctate.

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

Measurements in mm and Indices: TL 2.55-2.63; HL 0.58-0.60; HW 0.55-0.56; EL 0.04; SL 0.39-0.41; WL 0.69-0.71; PeL 0.18-0.19; PeW 0.33; HFeL 0.41; HTiL 0.32-0.34; HBaL 0.24-0.26; LS4 0.27-0.29; LT4 0.57-0.58; CI 93.3-94.8; SI 67.2-68.3; IGR 0.47-0.50.

Etymology
From the Latin pumilio (Lucretius, Seneca) = dwarf, pygmy, referred to the small size 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.