Tetramorium bessoni

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 : 141

Tetramorium bessoni Forel

(Fig. 9)

Tetramorium {Xiphomyrmex) bessonii Forel, 1891 a: 156 , pl. 4, figs 13,13 a. Syntype workers, Madagascar: Pays des Betsileo, Fianarantsoa (Besson) (MHN, Geneva) [examined]. Tetramorium (Xiphomyrmex) bessonii var. orientale Forel, 1895 a: 247 . Holotype worker, Madagascar: Imerina oriental (Sikora) (MHN, Geneva) [examined]. Syn. n.

Worker. TL 4.0 - 4.2, HL 0.88 - 0.90, HW 0.82 - 0.86, CI 90 - 95, SL 0.60 - 0.70, SI 74 - 80, PW 0.62 - 0.66, AL 1.08 - 1.14 (6 measured).

Mandibles striate, median clypeal and cephalic carinae well defined and distinct. Frontal carinae strongly developed but antennal scrobes weak. Propodeum armed with a pair of stout spines, the metapleural lobes low and rounded. In profile the petiole strongly antero-posteriorly compressed, thicksquamiform, the node much higher than long. Postpetiole also somewhat compressed. In dorsal view both petiole and postpetiole much broader than long. Clypeus with median and one or two pairs of lateral carinae, the spaces between them feebly or not sculptured. Dorsum of head with median carina and a few widely spaced, weak longitudinal rugulae on each side between median and frontal carinae. These rugulae variable, may be almost completely effaced to quite distinct. Ground-sculpture between the rugulae a very weak, superficial punctulation, again nearly effaced in some individuals. Dorsal alitrunk, pedicel and gaster unsculptured or at most with a few very faint rugulae in the vicinity of the metanotal groove. Erect to suberect hairs present on all dorsal surfaces of head and body but very sparse or (rarely) absent from the first gastral tergite. Colour a uniform medium-brown.

This species is closest related to humbloti , an African species which is known to occur on the Comoro Islands but has not yet been reported from Madagascar itself. The two are separated by sculpture, which on the head of humbloti is coarse and by the presence in bessoni of a number of erect or suberect hairs on the dorsal alitrunk, which is usually completely hairless in humbloti .

Material examined

Madagascar: La Mandraka (W. L. & D. E. Brown); Prov. Diego S., above Sakaramy (W. L. & D. E. Brown).