Monomorium afrum

Identification
Bolton (1987):

Worker. TL 3.6-4.3, HL 0.84-1.00, HW 0.66-0.80, CI 78-82, SL 0.72-0.85, SI 103-108, PW 0.46-0.52, AL 1.04-1.26 (35 measured).

Median portion of clypeus with its anterior free margin indented medially, the extent of the indentation varying in different populations from a narrow deep notch to a broad and quite deep concavity. Maximum diameter of eye 0.24-0.27 x HW, and with 10-12 ommatidia in the longest row. With head in profile the posteroventral angles bluntly right-angled or acute and narrowly rounded; not evenly broadly convex. Viewed from above and behind the posteroventral occipital angles are prominent and acute. Metanotal groove narrowly impressed. Dorsum of propodeum longitudinally impressed, the lateral margins of the impression diverging from front to back and frequently represented by a pair of sharp carinae, though in others the margins are merely bluntly rounded. Node of petiole in dorsal view with its posterior face shallowly transversely concave; degree of concavity varying between samples.

Head, alitrunk, petiole and postpetiole sharply and densely reticulate-punctate everywhere. First gastral tergite finely shagreenate, the sculpture sometimes fading apically on the sclerite. Head without standing hairs on dorsal surface behind level of frontal lobes or at most with a single pair mid-dorsally. Alitrunk without standing hairs; petiole with one pair, postpetiole with 1-2 pairs of backward directed hairs. First gastral tergite hairless except for the apical transverse row; these are usually appressed and may even be absent.

Colour uniform medium to dark brown, sometimes the gaster darker than the head and alitrunk. A widely distributed and very conspicuous species, afrum is easily identified within the salomonis-group by the combination of characters noted above. The shape of the posteroventral occipital angles is unique in the group and immediately isolates afrum.

Within the informal aggregation of species termed the opacum-complex afrum also separates from two other members by its lack of pilosity on the alitrunk, which is present in junodi and albopilosum.

Distribution based on Regional Taxon Lists
Afrotropical Region: Burkina Faso, Central African Republic, Democratic Republic of Congo, Eritrea, Ethiopia, Ghana, Ivory Coast, Kenya, Rwanda, Sudan, United Republic of Tanzania, Zimbabwe.

Nomenclature

 *  afrum. Monomorium afrum André, 1884a: 244 (w.) SUDAN. [Also described as new by André, 1884b: 540.] Arnold, 1926: 226 (q.); Wheeler, G.C. & Wheeler, J. 1955c: 124 (l.). Combination in M. (Xeromyrmex): Wheeler, W.M. 1922a: 868. Senior synonym of asmarensis, fultor: Bolton, 1987: 334.
 * asmarensis. Monomorium afrum var. asmarensis Forel, 1910c: 250 (w.m.) ETHIOPIA. Junior synonym of afrum: Bolton, 1987: 334.
 * fultor. Monomorium afrum var. fultor Forel, 1913b: 332 (w.) DEMOCRATIC REPUBLIC OF CONGO. Junior synonym of afrum: Bolton, 1987: 334.