Tetramorium petiolatum

Nothing is known about the biology of .

Identification
A member of the T. bicarinatum species group.

Sheela and Narendran (1998) - This species comes close to Tetramorium pacificum in the following characters: HW > 0.65mm, SL > 0.55mm, head rugosoreticulate, colour dark brown, TI with basal costulae. But it differs from pacificum in that (1) in the shape of petiole node-in this new species postero-dorsal angle of petiole node a little above antero-dorsal but not much higher as in pacifium (2) eye larger in size than pacificum (0.18-0.21 in pacificum, 0.24 in new species) (3) cephalic index 100 (in pacificum 83-90) and scape index 67 (79-87 in pacificum).

Distribution based on Regional Taxon Lists
Oriental Region: India.

Nomenclature

 *  petiolatum. Tetramorium petiolatus Sheela & Narendran, 1998a: 41, figs. 13-16 (w.) INDIA.

Worker
Holotype. Head finely reticulate including ventral side, on ventral side sculpture not strong as on dorsal side and becoming feeble towards mid ventral line; reticulation within scrobe smaller than those of remaining parts; mandibles smooth polished with hair pits, masticatory margin with three acute teeth at apex followed by two denticles and then a bare area at base; clypeus anterior margin medially indented and depressed, no flange, mid lobe with three median carinae which extend backwards up to middle of head and branched beyond posterior clypeal margin; median carina not extending up to anterior margin, weak sublateral carinae also present on clypeus; frontal area triangular, shallow; frontal carinae distinct extending up to occipital corners; scrobe shallow, eyes large, prominent, lateral, almost round, situated almost on mid line, a little upwards. Antennae 12-jointed, scape slender reaching just below occipital corners, flagellar segments 2-7 transverse, F8, subequal F1 and club elongate, club 3-jointed, thick, longer than remaining flagellar segments together (19:16), terminal club segment longer than preceding two together (10:9).

Thorax: finely reticulate, reticulations on dorsal surface large, spaces within reticulation smooth, neck of pronotum punctate; with a short median transverse carina, anteriorly broad, on pronotum, a slight depression just below anterior margin (excluding neck) anterolateral corners angulate, sutures absent, margin of mesometanotal junction constricted, propodeal spines erect, not cylindrical, somewhat prismatic, pointing backwards and outwards, extreme tip pointing upwards, its length about 3x distance between its bases, and 2.5x basal width; 1.7x length of peduncle of petiole; metapleural lobes acutely pointed at apex; fore coxae shagreened remaining parts of legs smooth; femora medially swollen, spurs on mid and hind tibiae slightly pectinate.

Abdomen: Peduncle of petiole weakly punctate, nodes reticulate, sculpture on postpetiole weaker than that on petiole; petiole quadrate, convex above, posterior face a little higher than anterior face; peduncle shorter than petiole node (6:10); node height and length subequal; anterior and posterior faces sub-parallel, postpetiole rounded, lower in a level than petiole, anterior face sloping, petiole dorsally longer than broad, postpetiole transverse. Gaster smooth .except few basigastral costulae, subglobose, first tergite covering more than 3/4 its length, anterior margin dorsoventrally with ridges.

Colour blackish brown, gaster darker than head and thorax; antennae, mandibles, legs, propodeal spines and apical margin of gastral tergites testaceous. Head, thorax, pedicel and abdomen with moderate amount of long and strong brownish yellow bristles, those on head and thorax, pedicel and abdomen with moderate amount of long and strong brownish yellow bristles, those on head and thorax erect, on pedicel suberect and on gaster subdecumbent; antennae and legs with abundant, short, decumbent hairs; femora with sparse long erect setae.

Total length-4mm; Head length-0.93mm; Head width-0.93mm; Cephalic index-100; Eye diameter-0.24mm; Scape length-0.62mm; Scape index-67; Pronotal width-0.64mm; Alitrunk length- 1.1mm.

Type Material
Holotype: Worker, India : Kerala, Muthanga, Sheela. S, 7.10.1995. (Department of Zoology, University of Calicut).

Etymology
The species name petiolatus indicates the peculiar shape of the petiole.