Tetramorium unicum

Bolton (1980) believed the holotype of this species is the specimen Wheeler (1922: 192) referred to as T. meressei. In that account Wheeler states: Dr. Bequaert took his specimen from one of the domatia of a Cuviera (probably C. angolensis), the other swellings of which were occupied by Engramma denticulatum (= Axinidris denticulata).

Identification
Bolton (1980) - I suspect that this specimen is the one identified by Wheeler (1922: 192) as T. meressei. The species is of course not closely related to T. meressei at all but forms a triad of species with Tetramorium quadridentatum and Tetramorium viticola which serves as the core of this group. It is quickly separated from both of these relatives by its lack of propodeal spines, having only a pair of minute denticles.

Distribution based on Regional Taxon Lists
Afrotropical Region: Cameroun, Democratic Republic of Congo, Uganda.

Nomenclature

 *  unicum. Tetramorium unicum Bolton, 1980: 366 (w.) DEMOCRATIC REPUBLIC OF CONGO.

Worker
Holotype. TL 3.7, HL 0.84, HW 0.70, CI 83, SL 0.60, SI 86, PW 0.54, AL 1.02.

Mandibles delicately longitudinally striate. Anterior clypeal margin entire, without a median notch. Median clypeal carina strongly developed and sharp, forming a narrow raised crest anteriorly and flanked on each side by another raised carina. Frontal carinae feeble and irregular, not more strongly developed than the remaining cephalic sculpture and merging into it just behind the level of the posterior margins of the eyes. Eyes quite large and prominent, situated in a shallowly concave circumocular area. Maximum diameter of eyes 0.20, about 0.29 x HW and with 11-12 ommatidia in the longest row. Propodeum in profile with a pair of minute denticles which, though broad-based, are very short, much shorter than the upcurved triangular metapleural lobes. Petiole in profile with the anterior and dorsal faces united in a single evenly convex curve, the dorsal surface weakly convex and sloping upwards posteriorly. Posterodorsal angle of node roughly right-angular or slightly more obtuse. Postpetiole in profile also with anterior and dorsal faces united in a single even convexity, the dorsum posteriorly with a bluntly prominent angle which overhangs a short but distinctly concave free posterior face. Node of petiole in dorsal view about as long as broad. Dorsum of head with irreguar low rounded longitudinal rugae which meander or are sinuate. A few inconspicuous cross-meshes are present on the dorsum and these are more numerous on the occiput, but a distinct occipital rugoreticulum is not developed. Ground-sculpture of head a fine superficial granulation. Dorsal alitrunk finely and very irregularly rugose, the rugae low and rounded and nowhere forming a sharp reticulum although numerous transverse or oblique short rugulae are present. Petiole and postpetiole with more sharply developed rugae than the alitrunk, mostly longitudinal but with a few meshes, and also with a fairly conspicuous dense punctulate ground-sculpture, especially on the latter segment. First gastral tergite very finely and densely punctulate everywhere, more sharply developed basally than apically. In the central portion of the tergite the punctulae are seen to be separated by small shiny interspaces, and are not confluent or reticulate-punctulate as is the case on the basal portion of the sclerite. All dorsal surfaces of the head and body with numerous quite stout hairs. Colour uniform yellowish brown.

Type Material
Holotype worker, Zaire (‘Congo’ on data label): Masaki near Masisi, 1°S; 28° 30’E, Cuviera (angolensis?), no. 158 (no collector’s name but probably J. Bequaert). Bolton. I suspect that this specimen is the one identified by Wheeler (1922: 192) as T. meressei, as the information given there certainly fits, in which case the collector is J. Bequaert.