Proceratium striativenter

The type was collected from rainforest leaf litter.

Identification
A member of the silaceum clade that is similar to Proceratium angulinode, with both having a postpetiole anteriorly concave and laterally angulate and the first gastral tergite with a thick, transversal border before the posterior margin. Proceratium striativenter differs from angulinode, in the worker, by the frontal carinae narrower, by the gaster completely covered by thicker, more regular, longitudinal rugosities, by the SI ≥ 75.6 instead of < 65 and by the TL > 3.3 mm instead of < 2.9 mm.

Distribution based on Regional Taxon Lists
Indo-Australian Region: Borneo, Indonesia, Malaysia.

Nomenclature

 *  striativenter. Proceratium striativenter De Andrade, in Baroni Urbani & De Andrade, 2003b: 379, figs. 3, 147 (w.) BORNEO.

Worker
Head as long as broad and with the sides gently diverging posteriorly. Vertex in full face view gently convex. Clypeus reduced and about as long as the antennal sockets. Anterior border of the clypeus truncate. Frontal carinae less broad than in angulinode, slightly covering the antennal insertions. Lateral expansions of the frontal carinae narrower than in angulinode, more raised than in angulinode, diverging on the anterior one-half, converging on the third fourth, parallel and carinate only on the last fourth. Frontal area gently concave on the second and third fourths and with a central, thick longitudinal carina starting from the last fourth and prolonging posteriorly. Head anterolaterally with a thick, short, longitudinal carina. Genal carinae marked, each carina corresponding to the external border of a deep sulcus. Eyes represented by a dark dot below the integument, small and placed on the middle of the head sides. First funicular joint slightly longer than 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 7-8 denticles before the pointed apical tooth. Palp formula 2,2.

Mesosoma in side view convex and about as long as the maximum head length (mandibles included). Pronotal and propodeal sutures absent. Basal face of the propodeum declivous posteriorly. Declivous face of the propodeum flat. Area between the basal and declivous faces of the propodeum weakly concave, with an irregular, transversal margin, the margin forming a large, lamelliform triangular tooth largely placed on the declivous face laterally. Propodeal lobes bearing a round, slightly lamellaceous border. Propodeal spiracle round and above mid height in lateral view.

Petiole subrectangular and thick. Anterior border of the petiole straight and anterolaterally carinate. Ventral process of the petiole large and triangular. Anterior face of the postpetiole concave and laterally angulate. Postpetiolar sternite anteromedially with a marked subtriangular projection, gently convex posteriorly in side view. Constriction between postpetiole and gaster impressed. Gastral tergite I about 1/4 longer than the postpetiole and convex on the curvature. Gastral tergite I with a thick, irregular, transversal folding before the posterior margin, the folding shorter than the posterior margin. Remaining gastral tergites and sternites curved ventrally.

Legs 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 slightly shorter than pretarsus. Pretarsal claws simple. Arolia absent.

Sculpture. Head, mesosoma, petiole and postpetiole with variably distributed, irregular, superficial, foveae-like impressions, granulopunctate and irregularly rugulose. The rugosities longer on the postpetiole. Gaster punctate and with almost longitudinal, thick rugosities. Legs punctate.

Pilosity as in angulinode.

Colour. Dark ferrugineous-brown with slightly lighter antennae and legs.

Measurements in mm and Indices: TL 3.41; HL 0.78; HW 0.77; EL 0.04; SL 0.59; WL 0.99; PeL 0.25; PeW 0.37; HFeL 0.62; HTiL 0.53; HBaL 0.38; LS4 0.30; LT4 0.65; CI 98.7; SI 75.6; IGR 0.46.

Etymology
From the Latin stria (= stripe, furrow) and venter (= belly, gaster), referred to the integumental structure of the gaster 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.
 * CSIRO Collection
 * Pfeiffer M.; Mezger, D.; Hosoishi, S.; Bakhtiar, E. Y.; Kohout, R. J. 2011. The Formicidae of Borneo (Insecta: Hymenoptera): a preliminary species list. Asian Myrmecology 4:9-58