Tetramorium convexum

Noted as being a "minute...leaf-litter inhabiting species" by Bolton (1980), which is presumably based on information passed on to him by the collector of the types, P. Room.. This species is only known from the type series (3 workers).

Identification
Bolton (1980) - A member of the Tetramorium convexum species group. A minute but easily defined leaf-litter inhabiting species, T. convexum does not appear to have any known close relatives. It is grouped for convenience here with Tetramorium wadje as the two have a number of characters in common (see species-group diagnosis) but I am sure that these have been acquired convergently and do not represent a true relationship. Tetramorium convexum is isolated from all other species with 12-merous antennae by its combination of very small size, smooth mandibles, entire clypeal margin, very short frontal carinae, reduced sculpture, absolutely unarmed propodeum, fine acute pilosity, and standing pubescence on the appendages. It is tempting to associate T. convexum with the members of the simillimum-group, but the form of the pilosity and the presence of standing pubescence on the scapes and tibiae militate against it. Similarly, many of its characters are in accord with those seen in Tetramorium caespitum and its allies, but the form of the petiole is wrong, the pronotal angles are rounded in T. convexum and the head does not have the broad, flattened aspect of the caespitum-group members. It corresponds in many respects with the smaller, less strongly sculptured species of the shilohense-group (subcoecum-complex) but of course in these forms the eyes are very small or minute, whilst the eyes of T. convexum are quite large and conspicuous. As stated above, it is grouped here with T. wadje, for the sake of convenience, another species without obvious relatives. The two are easily separable as T. convexum has erect hairs on the dorsal alitrunk and the propodeum is unarmed, whilst in T. wadje erect hairs are absent and the propodeum has a pair of short triangular teeth.

Distribution based on Regional Taxon Lists
Afrotropical Region: Ghana.

Nomenclature

 *  convexum. Tetramorium convexum Bolton, 1980: 322 (w.) GHANA.

Worker
Holotype: TL 1.9, HL 0.46, HW 0.38, CI 83, SL 0.26, SI 68, PW 0.26, AL 0.52. Paratypes (2 measured): TL 1.9-2.0, HL 0.46-0.47, HW 0.39-0.40, CI 84-85, SL 0.27-0.28, SI 69-70, PW 0.26, AL 0.52-0.54. Maximum diameter of eye 0.10, about 0.25-0.26 x HW.

Mandibles smooth and shining, highly polished and with a few minute pits. Anterior clypeal margin convex, without trace of a median notch or impression. Median clypeal carina absent, the clypeus unsculptured. Frontal carinae very short and weak, ending in front of the level of the midlengths of the eyes. Antennal scrobes completely absent. Scapes relatively short and stout (SI range 68-70). Eyes at the exact midlength of the sides of the head, maximum diameter of eye 0.10, about 0.26 x HW, with 6-7 ommatidia in the longest row. The eyes are roughly circular in outline, the longitudinal axis only minimally greater than the vertical. Alitrunk in profile with an extremely shallow flattened area between promesonotum and propodeum forming a vestigial impression. Propodeum absolutely unarmed, without the slightest trace of spines or teeth, the dorsum and declivity meeting in an even, shallowly convex curve. Metapleural lobes reduced to a pair of narrow, low blunt flanges. Petiole in profile with a short, thick anterior peduncle the dorsal surface of which forms a shallowly concave arc with the anterior face of the node. Petiole node itself squat and low, with both antero- and posterodorsal angles blunt. In dorsal view the node subglobular, rounded and slightly broader than long. Dorsum of head mostly smooth and shining, with only the faintest vestiges of undefined sculpture between the remnants of the frontal carinae and with 2-3 very feeble short striae immediately behind the posterior clypeal margin. Dorsal alitrunk with a few very weak longitudinal rugulae and the petiole also with some faint fine rugulae visible. Postpetiole with only the most minute vestiges of rugular sculpture. Gaster smooth and shining. All dorsal surfaces of head and body with numerous fine, soft hairs which are acute apically. Antennal scapes and dorsal (outer) surfaces of middle and hind tibiae with short suberect to subdecumbent pubescence. Head dark brown, the remainder of the body and the appendages dull yellow, much lighter in shade than the head.

Paratypes: As holotype but one with a single feeble lateral rugula on the clypeus.

Type Material
Holotype worker, Ghana: Aburi, 11.v.1969 (P. Room). Paratypes. 2 workers with same data as holotype (BMNH; ).

References based on Global Ant Biodiversity Informatics

 * Bolton B. 1980. The ant tribe Tetramoriini (Hymenoptera: Formicidae). The genus Tetramorium Mayr in the Ethiopian zoogeographical region. Bulletin of the British Museum (Natural History). Entomology 40: 193-384.