Tetramorium xuthum

When first found the workers were running about in bright sunlight and attacking workers of a Pheidole species to which they had a close superficial resemblance. The Pheidole were seized and carried off by T. xuthum, not just attacked.

Identification
Bolton (1980) - Tetramorium xuthum is presently the only member of the bequaerti-complex (also Tetramorium bequaerti, Tetramorium bulawayense, Tetramorium hortorum) which occurs in West Africa. It is also a very conspicuous species within the complex, immediately separable by its exceptionally dense pilosity, short dentiform propodeal armament and dark colour. In the other three species standing hairs on the scapes and tibiae are short, stout and blunt, and are quite sparse, there being distinct gaps between one hair and the next. In T. xuthum, on the other hand, these hairs are densely packed together and are fine and acute.

Distribution based on Regional Taxon Lists
Afrotropical Region: Ghana.

Nomenclature

 *  xuthum. Tetramorium xuthum Bolton, 1980: 335 (w.) GHANA.

Worker
Holotype. TL 3.3, HL 0.74, HW 0.62, CI 84, SL 0.70, SI 113, PW 0.46, AL 0.94. Paratype: TL 3.4, HL 0.74, HW 0.62, CI 84, SL 0.72, SI 116, PW 0.46, AL 0.92.

Mandibles strongly longitudinally striate. Anterior clypeal margin entire. Median clypeal carina sharp and distinct. Frontal carinae short and feeble, divergent and ending at the level of the anterior margins of the eyes. Antennal scrobes absent, the head evenly convex across the eyes. Antennal scapes long, SI > 100. Maximum diameter of eye 0.18, about 0.29 x HW and with 11-12 ommatidia in the longest row. Propodeum armed with a pair of short triangular teeth which are distinctly shorter than the upcurved triangular metapleural lobes. Petiole in profile elongate-nodiform, the length of the dorsum greater than the height of the tergal portion. In dorsal view the node long and narrow, distinctly much longer than broad. Dorsum of head with fine longitudinal rugulae which are only feebly developed but are quite dense. Spaces between them with a very fine superficial punctulate ground-sculpture. Dorsal alitrunk finely and densely longitudinally rugulose on the promesonotum, the rugulae more disorganized on the propodeum but everywhere with fine superficial punctulate ground-sculpture. Petiole and postpetiole delicately rugulose and punctulate. First gastral tergite shagreened and opaque basally. All surfaces of head and body densely clothed with a pelt of short, fine, acute hairs which even arise on the sides of the alitrunk and from between the facets of the eyes. Sides of head behind eyes with abundant projecting hairs, too many to be counted easily with the head in full-face view. Antennal scapes and dorsal (outer) surfaces of middle and hind tibiae similarly clothed in a dense pelt of short, fine suberect to subdecumbent hairs. Colour uniform dark brown.

Paratype: As holotype.

Type Material
Holotype worker, Ghana: Tafo, 15.ix.1970, on bare ground in bright sunlight (B. Bolton). Paratype. 1 worker with same data as holotype.