Tetramorium

Wheeler, W. M., 1922, The ants collected by the American Museum Congo Expedition., Bulletin of the American Museum of Natural History 45, pp. 39-269 : 190-191

Tetramorium Mayr

Worker small, monomorphic. Antennae 12-jointed, with a 3-jointed club. Clypeus narrowed on the sides where its posterior margin is raised in the form of a short trenchant ridge or carina as the anterior border of the antennal socket. Frontal carinae rather far apart, usually continued back some distance and often the full length of the head as subparallel ridges forming the inner borders of scrobes or demiscrobes for the accommodation of the antennal scapes. Maxillary palpi 4-jointed; labial palpi 3-jointed. Eyes well developed; ocelli absent. Mandibles rather large, triangular, their apical border with a few large and several small teeth. Premesonotal suture indistinct, mesoepinotal suture more or less distinct; mesoepinotal constriction usually feeble; epinotum with two spines or teeth and episterna usually spined or dentate. Petiole with a short but distinct peduncle and the node large, subcuboidal, rounded above, rarely squamiform; the postpetiole usually broader than the petiole. Legs rather short, middle and hind tibiae with small, simple spurs. Head, thorax, and petiole sculptured, usually rugose or reticulate rugose.

Female resembling the worker, but somewhat larger. Pronotum usually very little exposed above; mesonotum and scutellum raised above the level of the pro- and epinotum, the latter with stouter and shorter spines than in the worker. Fore wing with one cubital, one discoidal, and a closed radial cell.

Male slightly smaller than the female, with 10-jointed, very exceptionally with 12- or 13-jointed antennae. Second funicular joint very long, representing a fusion of 4 joints. Head small, ocelli and eyes large. Mandibles small but dentate. Pronotum overarched by the mesonotum, which has distinct Mayrian furrows. Epinotum truncate and dentate. Wings as in the female.

This genus might be described as peculiar to the Old World, because nearly all the few species occuring in America ( T. caespitum , simillimum , and guineense ) are known to have been introduced by commerce. The group reaches its greatest development in the Ethiopian Region so far as the number of species, subspecies, and varieties is concerned. Arnold has included Triglyphothrix, Xiphomyrmex , and Decamorium as subgenera, but I have treated them as genera, though a few species with simple hairs may be assigned indifferently either to Tetramorium or Triglyphothrix. I have still further reduced the size of the genus Tetramorium by establishing a new genus, Macromischoides , for T. africanum and aculeatum (vide supra). The species of Tetramorium form moderately large colonies and nest in the ground, usually under stones or logs. One of the species, T. caespitum , has a remarkable distribution, ranging from Britain to Japan, around the shores of the Mediterranean, and reappearing at higher elevations on Mt. Kilimanjaro.