Tetramorium tosii Emery

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 : 153

Tetramorium tosii Emery

(Figs 32, 33)

Tetramorium tosii Emery, 1899: 284 , fig. Syntype worker, Madagascar: Bai d'Antongil (Mocquerys) (MHN, Geneva) [examined].

Worker. TL 5.2, HL 1.14, HW 0.98, CI 86, SL 0.96, SI 98, PW 0.76, AL 1.40.

Mandibles striate, anterior clypeal margin convex and entire. Clypeus with three very sharply raised longitudinal carinae running its length. Frontal carinae strong, running back well beyond the level of the eyes, becoming indistinguishable from the rugoreticulum on the occipital corners. Antennal scapes moderately long, SI approaching 100. Eyes unique in the genus, moderately sized but very strongly protuberant, projecting on each side of the head as a dome-shaped, strongly convex hemisphere. Occipital margin broadly and deeply concave in full-face view. Outline shape of alitrunk as in Fig. 33. Propodeum armed with a pair of very long, narrow, acute spines; metapleural lobes broadly triangular and feebly upcurved. Petiole in profile with an extremely long, curved peduncle anteriorly and with a long, low node which slopes upwards posteriorly. Shape of petiole in lateral and dorsal view as in Fig. 33. Dorsum of head sculptured with five coarse longitudinal rugae or carinae between the frontal carinae, the dorsal surfaces of which are finely beaded. A loose reticulum formed by widely spaced cross-meshes is present occipitally, and a reticulum is more strongly developed on the sides above and behind the eyes. Dorsal alitrunk largely unsculptured, with only scattered vestiges of low rugulae, the spaces between which are shining and have a fine superficial reticular ground-sculpture. Sides of pronotum much more strongly sculptured than dorsum. Sides of petiole with rugulose sculpture, but the dorsum and the entire postpetiole only with fine, faint superficial punctulation. First gastral tergite with faint superficial minute reticular markings, otherwise unsculptured. All dorsal surfaces with numerous fine erect or suberect hairs but these absent from the appendages where only fine pubescence is present. Colour uniform dark reddish brown, the gaster slightly darker in shade than the head and alitrunk.

This large and spectacular species is not referable to any other species-group except in the vaguest ways. Its affinities seem to lie in the direction of the tortuosum-group, but there the antennae have only 11 segments and the sting appendage is spatulate, whereas in tosii the antennae are 12 - merous and the sting appendage is pennant-shaped.

T. tosii should not be confused with any other Malagasy species as its combination of 12 - merous antennae and unique eye-structure makes it immediately recognizable. It is separable from tantillum , its only known relative, by the different eye structure, size, shape of petiole and length of propodeal spines (compare Figs 30, 31 and 32, 33).