Tetramorium isectum, 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 : 145

Tetramorium isectum sp. n.

(Figs 17, 18)

Holotype worker. TL 4.1, HL 0.96, HW 0.92, CI 96, SL 0.72, SI 78, PW 0.68, AL 1.12.

Mandibles strongly longitudinally striate, anterior clypeal margin with a distinct median impression. Eyes small, maximum diameter 0.14, about 0.15 x HW. Frontal carinae long and strong, running back to the occipital corner in full-face view and surmounted throughout their length by a narrow raised rim or flange. Antennal scrobes shallow and feeble, the sides of the head above the eye regularly longitudinally rugulose. Occipital margin of head markedly concave in full-face view, the sides shallowly but evenly convex. Pronotal dorsum transversely concave, the mesonotum and propodeum more or less flat. Anterior pronotal angles rounded in dorsal view. Propodeal spines elongate and narrow, elevated and feebly upcurved along their length. Metapleural lobes elongate triangular and acute. Shape of petiole as in Fig. 18, in dorsal view longer than broad and broader behind than in front. Clypeus with three longitudinal carinae. Dorsum of head strongly and regularly longitudinally rugose, the spaces between them with very faint superficial punctulation and with about 8 strong rugae between the frontal carinae at eye-level. Cross-meshes or anastomoses absent except laterally on the occiput. Dorsal alitrunk with very strongly raised longitudinal rugae, the five central ones of which run from pronotum to propodeum (the middle three most strongly defined). Outside these on the pronotum some rugoreticulum is present around the anterior angles, but this is absent elsewhere on the dorsal alitrunk. Dorsal surfaces of petiole and postpetiole rugulose, gaster unsculptured. All dorsal surfaces of body with abundant fine pilosity. Colour bright orange-brown.

Holotype worker, Madagascar: Beforona, 500 m, Sept. 1974, forest humus and litter (A. Peyrieras) (MCZ, Cambridge).

T. isectum is closest related to andrei and robustior , but the combination of small eyes, bright orange-brown colour, concave pronotum and very sharply defined longitudinal sculpture easily isolates this species.