Monomorium afrum

Widely distributed and seemingly common across the Sahel and southwards in East Africa. Known from mango (Mangifera indica) orchards, beating weeds near a river and Acacia gourmaensis and on Terminalia laxiflora. It is ground nesting (Taylor et al., 2018). Arnold (1916) records that it forms populous nests in the soil, generally in exposed or sunny situations. Wheeler (1922) notes that it appeared in large numbers at the carcase of a bird. Whether scavenging represents the main feeding method or whether it is an opportunist, 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

 * . Monomorium afrum André, 1884a: 244 (w.) SUDAN (date of publication 15.iv.1884).
 * Type-material: syntype workers (number not stated).
 * Type-locality: Sudan: Atbara (P. Magretti).
 * Type-depository: MNHN.
 * [Also described as new by André, 1884b: 540 (date of publication 15.xi.1884).]
 * Arnold, 1926: 226 (q.); Wheeler, G.C. & Wheeler, J. 1955c: 124 (l.).
 * Combination in M. (Xeromyrmex): Wheeler, W.M. 1922a: 868.
 * Status as species: Dalla Torre, 1893: 65; Forel, 1913a: 136; Santschi, 1914b: 72; Arnold, 1916: 206; Emery, 1922e: 176; Wheeler, W.M. 1922a: 163, 868; Arnold, 1926: 226; Menozzi, 1933a: 103; Finzi, 1939a: 158; Prins, 1963: 103; Ettershank, 1966: 87; Collingwood, 1985: 269; Bolton, 1987: 334 (redescription); Bolton, 1995b: 258; Hita Garcia, et al. 2013: 212; Borowiec, L. 2014: 115; Madl, 2019: 15.
 * Senior synonym of asmarensis: Bolton, 1987: 334; Bolton, 1995b: 259.
 * Senior synonym of fultor: Bolton, 1987: 334; Bolton, 1995b: 259.
 * Distribution: Central African Republic, Democratic Republic of Congo, Eritrea, Ethiopia, Ghana, Ivory Coast, Kenya, Rwanda, Tanzania, Saudi Arabia, South Africa, Sudan, Zimbabwe.
 * asmarensis. Monomorium afrum var. asmarensis Forel, 1910c: 250 (w.m.) ERITREA.
 * Type-material: syntype workers, syntype males (numbers not stated).
 * Type-localities: Eritrea: Asmara, 1906 (K. Escherich), Nefassit, iii.1906 (K. Escherich), Ghinda, 1906 (K. Escherich).
 * Type-depository: MHNG.
 * Subspecies of afrum: Wheeler, W.M. 1922a: 868; Emery, 1922e: 176; Viehmeyer, 1923: 91; Finzi, 1939a: 158; Ettershank, 1966: 87.
 * Junior synonym of afrum: Bolton, 1987: 334; Bolton, 1995b: 259.
 * fultor. Monomorium afrum var. fultor Forel, 1913b: 332 (w.) DEMOCRATIC REPUBLIC OF CONGO.
 * Type-material: syntype workers (number not stated).
 * Type-locality: Democratic Republic of Congo (“Congo belge”): Katanga, Sankisia, 6.viii.1911 (Bequaert).
 * Type-depositories: MHNG, MRAC.
 * Subspecies of afrum: Wheeler, W.M. 1922a: 163, 868; Emery, 1922e: 176; Ettershank, 1966: 89.
 * Junior synonym of afrum: Bolton, 1987: 334; Bolton, 1995b: 262.

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

 * Bolton B. 1987. A review of the Solenopsis genus-group and revision of Afrotropical Monomorium Mayr (Hymenoptera: Formicidae). Bulletin of the British Museum (Natural History). Entomology 54: 263-452.
 * 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.
 * Finzi B. 1939. Materiali zoologici dell'Eritrea raccolti da G. Müller durante la spedizione dell'Istituto Sieroterapico Milanese e conservati al Museo di Trieste. Parte III. Hymenoptera: Formicidae. Atti del Museo Civico di Storia Naturale di Trieste 14: 153-168.
 * Forel A. 1910. Ameisen aus der Kolonie Erythräa. Gesammelt von Prof. Dr. K. Escherich (nebst einigen in West-Abessinien von Herrn A. Ilg gesammelten Ameisen). Zoologische Jahrbücher. Abteilung für Systematik, Geographie und Biologie der Tiere 29: 243-274.
 * Garcia F.H., Wiesel E. and Fischer G. 2013.The Ants of Kenya (Hymenoptera: Formicidae)Faunal Overview, First Species Checklist, Bibliography, Accounts for All Genera, and Discussion on Taxonomy and Zoogeography. Journal of East African Natural History, 101(2): 127-222
 * IZIKO South Africa Museum Collection
 * Kolo Y. 2006. Evaluation rapide des fourmis de la région de Boké, Guinée. In Wright, H.E. and J. McCullough et M.S. Diallo. (eds). 2006. A Rapid Biological Assessment of the Boké Préfecture, Northwestern Guinea. RAP Bulletin of Biological Assessment 41. Conservation International, Washington, DC.
 * Kouakou L. M. M., K. Yeo, K. Ouattara, W. Dekoninck, T. Delsinne, and S. Konate. 2018. Investigating urban ant community (Hymenoptera: Formicidae) in port cities and in major towns along the border in Côte d’Ivoire: a rapid assessment to detect potential introduced invasive ant species. Journal of Animal and Plant Sciences 36(1): 5793-5811.
 * Kouakou L. M. M., W. Dekoninck, M. Kone, T. Delsinne, K. Yeo, K. Ouattara, and S. Konate. 2018. Diversity and distribution of introduced and potentially invasive ant species from the three main ecoregions of Côte d’Ivoire (West Africa). Belgian Journal of Zoology 148 (1): 83–103.
 * Madl M. 2019. Notes on the ant fauna of Eritrea (Insecta: Hymenoptera: Formicidae): type specimens deposited in the Natural History Museum Vienna (Austria) and a preliminary checklist. Ann. Naturhist. Mus. Wien, B 121: 9-18.
 * Prins A. J. 1963. A list of the ants collected in the Kruger National Park with notes on their distribution. Koedoe 6: 91-108.
 * Prins A. J. 1964. Revised list of the ants collected in the Kruger National Park. Koedoe 7: 77-93.
 * Taylor B., N. Agoinon, A. Sinzogan, A. Adandonon, Y. N'Da Kouagou, S. Bello, R. Wargui, F. Anato, I. Ouagoussounon, H. Houngbo, S. Tchibozo, R. Todjhounde, and J. F. Vayssieres. 2018. Records of ants (Hymenoptera: Formicidae) from the Republic of Benin, with particular reference to the mango farm ecosystem. Journal of Insect Biodiversity 8(1): 006–029.
 * 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
 * Yeo K., S. Konate, S. Tiho, and S. K. Camara. 2011. Impacts of land use types on ant communities in a tropical forest margin (Oumé - Cote d'Ivoire). African Journal of Agricultural Research 6(2): 260-274.
 * Yeo K., T. Delsinne, S. Komate, L. L. Alonso, D. Aidara, and C. Peeters. 2016. Diversity and distribution of ant assemblages above and below ground in a West African forest–savannah mosaic (Lamto, Cote d’Ivoire). Insectes Sociaux DOI 10.1007/s00040-016-0527-6