Proceratium ivimka

Some of the type material was collected in a lowland wet forest, in a sample of sifted leaf litter and debris from a rotten log.

Identification
A Proceratium species belonging to the silaceum clade resembling Proceratium austronesicum but differing from it, in the worker, by the smaller size (TL ≤ 2.30 mm instead of ≥ 2.70 mm), by the hairs of type (1) sparser on the gaster and by the first gastral tergite less convex. (Baroni Urbani and de Andrade 2003)

Distribution
Known only from Papua New Guinea.

Distribution based on Regional Taxon Lists
Indo-Australian Region: New Guinea.

Nomenclature

 *  ivimka. Proceratium ivimka De Andrade, in Baroni Urbani & De Andrade, 2003b: 320, fig. 130 (w.) NEW GUINEA.

Worker
Head slightly longer than broad and with the sides gently diverging posteriorly. Vertex in full face view weakly convex. Clypeus reduced and as long as the antennal sockets. Anterior border of the clypeus truncate. Frontal carinae not very broad, not covering the antennal insertions. Lateral expansions of the frontal carinae narrow, little raised, diverging on the two anterior fourths, converging on the third fourth, diverging and carinate only on the last fourth. Frontal area gently concave on the three anterior fourths 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 deep sulcus. Eyes visible as a dark dot below the integument, small and on the middle of the head sides. First funicular joint slightly broader than 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 7-8 denticles before the pointed apical tooth. Palp formula 2,2.

Mesosoma convex in profile and slightly shorter than maximum head length (mandibles included). Pronotal and propodeal sutures absent. Basal face of the propodeum declivous posteriorly. Declivous face of the propodeum gently sloping posteriorly. Sides between the basal and declivous faces of the propodeum minutely denticulate. Sides of the declivous face superficially carinate. Propodeal spiracle round and above mid height in lateral view.

Petiole subrectangular and flattened. Anterior border of the petiole straight and anterolaterally carinate. Ventral process of the petiole small and pointed backwards. Postpetiole in dorsal view with posteriorly diverging sides. Postpetiolar sternite anteromedially with a marked subtriangular projection and gently convex posteriorly in side view. Constriction between postpetiole and gaster impressed. Gastral tergite I about 1/3 longer than the postpetiole and slightly convex on the curvature. Remaining gastral tergites and sternites curved ventrally.

Legs short. Fore tibiae incrassate. Mid and hind tibiae slightly incrassate. All tibiae with a pectinate spur. Spurs of forelegs without basal spine. Fore basitarsi longer than the mid ones. Wind basitarsi about 1/3 shorter than hind tibiae. Second tarsomere of hind legs shorter than pretarsus. Pretarsal claws simple. Arolia small but present.

Sculpture. Head minutely punctate; antero-dorsal and lateral parts of the head irregularly rugulose. Mesosoma, petiole, postpetiole and gaster punctate, the punctures absent from the posterodorsal part of the first gastral tergite which is smooth and with sparse piligerous punctures. Legs minutely punctate.

Body covered by hairs of three main types: (1) short, dense, subdecumbent on the whole body, sparser and slightly longer on the second gastral tergite, suberect and sparse on the funicular joints; (2) longcr than typc (1), erect on the whole body, absent from 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) but slightly shorter.

Colour. Dark brown-black with lighter anterior half of the head dorsum, antennae and legs.

Measurements in mm and Indices: TL 2.20-2.30; WL 0.51-0.53; HW 0.48-0.50; EL 0.03; SL 0.34-0.35; WL 0.61-0.63; PeL 0.15-0.16; PeW 0.23-0.24; HFeL 0.34-0.35; HTiL 0.28-0.31; HBaL 0.20-0.21; LS4 0.24-0.25; LT4 0.47-0.51; CI 94.1-94.4; SI 64.8-66.7; IGR 0.49-0.51.

Type Material
Holotype worker from Papua New Guinea labeled: "PNG. Gulf Prov.: Ivimka camp. Lakekamu Basin, 7.7°S 146.8°E 400 m el, 20 Nov. 1996, coll R. R. Snelling # 96-350, lowland wet forest: sifted leaf litter & debris from rotten log"; 1 paratype worker labeled: "PNG. Gulf Prov.: Ivimka camp, Lakeknmu Basin, 07.73°S 146.76°E 110 m, 14 Nov 1996, R. R. Snelling # 96-325", both in.

Etymology
Ivimka is the name of the locality where the species was collected by Roy Snelling. It is used here as a specific name in apposition as suggested by Roy.

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.
 * Janda M., G. D. Alpert, M. L. Borowiec, E. P. Economo, P. Klimes, E. Sarnat, and S. O. Shattuck. 2011. Cheklist of ants described and recorded from New Guinea and associated islands. Available on http://www.newguineants.org/. Accessed on 24th Feb. 2011.