Tetramorium plesiarum, Bolton, B., 1979

Bolton, B., 1979, The ant tribe Tetramoriini (Hymenoptera: Formicidae). The genus Tetramorium Mayr in the Malagasy region and in the New World., Bulletin of the British Museum (Natural History) Entomology 38, pp. 129-181 : 150

Tetramorium plesiarum sp. n.

(Fig. 27)

Holotype worker. TL 30, HL 0.74, HW 0.69, CI 93, SL 0.48, SI 69, PW 0.52, AL 0.84.

Mandibles very delicately longitudinally striate, anterior clypeal margin with a narrow median impression. Eyes moderate, maximum diameter 0.14, about 0.20 x HW, the maximum diameter with about 8 facets. Frontal carinae strong, surmounted by a narrow rim or flange and forming the upper margins of the strongly developed scrobes, which are bounded below by a strong longitudinal carina running above the eye and are divided into upper and lower portions by a strong median longitudinal carina which runs back well beyond the level of the posterior margin of the eye. The posterior margin of the scrobe is bounded by a downcurvature of the frontal carina which is directed towards the lower occipital corner (Fig. 27). Propodeum armed with a pair of narrow spines which are slightly upcurved along their length, the metapleural lobes elongate-triangular and acute. Petiole in profile high and quite narrow, the dorsal length less than the height of the tergal portion of the node. Postpetiole regularly convex. Petiole in dorsal view distinctly broader than long. Dorsum of head irregularly longitudinally rugulose, the interspaces with fine superficial punctulation. Dorsal alitrunk with spaced-out longitudinal rugulae, without transverse sculpture except on the extreme anterior pronotum. Spaces between rugulae glossy, with very feeble groundsculpture. Dorsal surfaces of petiole and postpetiole unsculptured although the sides of these segments have some dense but faint punctulation. Gaster unsculptured. All dorsal surfaces of head and body with abundant fine pilosity. Colour brown.

Holotype worker, Madagascar: Causse de Kelifely, 20 - 30. xi. 1974, forest humus and litter, dry forest (A. Peyrieras) (MCZ, Cambridge).

From the overall appearance of this species, and especially because of the strongly developed scrobes and dense pilosity, it seems to be an attempt by a member of the ranarum-group to acquire a Triglyphothrix-like habitus (but of course without the branched hairs), and these characters separate it well from related species in this group. The development of the scrobe is along the same lines but less complete in zenatum , but in this species the petiole node has a characteristic and very distinctive shape (Fig. 19).