Monomorium afrum

Arnold (1916) records that afrum forms populous nests in the soil, generally in exposed or sunny situations. Wheeler (1922) notes that the ants appeared in large numbers at the carcase of a bird. Whether scavenging represents the main feeding method of afrum or whether they are opportunists, both scavenging and indulging in active predation when possible, is not known.

Identification
Bolton (1987) - A member of the M. opacum complex in the M. salomonis species group. A widely distributed and very conspicuous species, afrum is easily identified within the salomonis-group by the combination of characters noted in the descrpition. The shape of the posteroventral occipital angles is unique in the group and immediately isolates afrum.

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

The female of afrum shows some modifications characteristic of the socially parasitic species Monomorium santschii and Monomorium effractor, and may itself found new colonies by a temporary socially parasitic process.

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.

Worker
Bolton (1987) - 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.

Type Material
Bolton (1987) - Syntype workers, Sudan: Atbara (Magretti) (examined).

References based on Global Ant Biodiversity Informatics

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 * Borowiec L., and S. Salata. 2018. Notes on ants (Hymenoptera: Formicidae) from Gambia (Western Africa). Annals of the Upper Silesian Museum in Bytom Entomology 26: 1-13.
 * Emery C. 1915. Formiche raccolte nell'Eritrea dal Prof. F. Silvestri. Bollettino del Laboratorio di Zoologia Generale e Agraria della Reale Scuola Superiore d'Agricoltura. Portici 10: 3-26.
 * Ettershank G. 1966. A generic revision of the world Myrmicinae related to Solenopsis and Pheidologeton (Hymenoptera: Formicidae). Aust. J. Zool. 14: 73-171.
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 * Viehmeyer H. 1923. Wissenschaftliche Ergebnisse der mit Unterstützung der Akademie der Wissenschaften in Wien aus der Erbschaft Treitl von F. Werner unternommenen zoologischen Expedition nach dem anglo-ägyptischen Sudan (Kordofan) 1914. VII. Hymenoptera A. Formicidae. Denkschriften der Akademie der Wissenschaften in Wien. Mathematisch-Naturwissenschaftliche Klasse 98: 83-94.
 * Wheeler W. M. 1922. Ants of the American Museum Congo expedition. A contribution to the myrmecology of Africa. II. The ants collected by the American Museum Congo Expedition. Bulletin of the American Museum of Natural History 45: 39-269.
 * Wheeler W. M. 1922. Ants of the American Museum Congo expedition. A contribution to the myrmecology of Africa. VIII. A synonymic list of the ants of the Ethiopian region. Bulletin of the American Museum of Natural History 45: 711-1004
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