Tetramorium buthrum

Identification
A member of the Tetramorium simillimum species group.

Bolton (1980) - In the simillimum-complex of this group the six species constituting the complex are characterized by their possession of strongly developed frontal carinae and antennal scrobes. Of the six, four have a very strong blanketing reticulate-punctate ground-sculpture on the head and elsewhere, but this is absent in the two species Tetramorium anxium and T. buthrum. The two species are separated by the relative lengths of the scapes (SI 82-83 in T. anxium, 90-93 in T. buthrum) and by the fact that the dorsum of the head is more densely rugulose in T. anxium, there being 8-10 feeble rugulae between the frontal carinae at eye level as opposed to 5 in T. buthrum.

Distribution based on Regional Taxon Lists
Afrotropical Region: Central African Republic.

Nomenclature

 *  buthrum. Tetramorium buthrum Bolton, 1980: 309 (w.) CENTRAL AFRICAN REPUBLIC.

Worker
Holotype: TL 2.2, HL 0.52, HW 0.44, CI 85, SL 0.40, SI 91, PW 0.32, AL 0.57. Paratypes (4 measured): TL 2.2-2.3, HL 0.52-0.54, HW 0.44-0.48, CI 85-89, SL 0.40-0.43, SI 90-93, PW 0.32-0.35, AL 0.57-0.64. Maximum diameter of eye 0.11-0.12, about 0.25-0.26 x HW. Maximum separation of frontal carinae at level of eyes 0.23-0.26, about 0.52-0.55 x HW.

Mandibles finely shagreened. Anterior clypeal margin entire, without a median impression, regularly arcuate and with the median carina strongly developed. Frontal carinae reaching back almost to occipital Margin, strongly developed, obviously more robust than any other cephalic sculpture and feebly elevated throughout their length; maximum separation of frontal carinae at level of eyes 0.24, c. 0.55 x HW. Antennal scrobes conspicuous, forming a shallow concavity in the side of the head which occupies all the space between the frontal carina and the eye on each side and which extends back almost to the occipital corner. Antennal scapes relatively long for a member of this group, SI 90 or more in all members of typeseries (a figure not usually attained in simillimum-group members). Maximum diameter of eye 0.11, about 0.25 x HW and with 6-7 ommatidia in the longest row. Propodeum armed with a pair of short triangular teeth which are slightly shorter and distinctly narrower than the metapleural lobes. Petiole in dorsal view slightly broader than long. Dorsum of head feebly sculptured, with only 5 weak longitudinal rugulae of which 3 are relatively more strongly developed than the other 2, which are exceedingly weak. Groundsculpture of dorsal head vestigial, no more than a slight roughening of the surface, the area glossy. Scrobal areas of sides of head glossy, with only vestigial ground-sculpture. Dorsal surfaces of alitrunk, petiole and postpetiole unsculptured except for scattered faint superficial punctulae. First gastral tergite unsculptured. All dorsal surfaces of head and body with scattered short, stout, blunt hairs which are more or less straight. Tibiae of middle and hind legs only with short, fine appressed pubescence. Colour dark brown, glossy; appendages lighter, yellowish brown.

Paratypes: As holotype but in some with another pair of cephalic rugulae visible which are, however, very feeble indeed. One or two faint longitudinal rugulae may be present on the pronotal dorsum and the mandibles vary from lightly shagreened to more or less smooth.

Type Material
Holotype worker, Central African Empire (‘Fr. Equat. Afr., Ubangi-Shari’ on data label): Haut Mbomu, iii.1948, no. 2188 (N. A. Weber). Paratypes. Central African Empire: 2 workers with same data as holotype. Zaire (‘B. Congo’ on data label): 2 workers, Niangara, ii-iii.1948, no. 2157 (N. A. Weber). (MCZ; )

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.