Monomorium opacum

Identification
Bolton (1987) - M. opacum is characterized by its dense, sharply defined reticulate-punctate sculpture, sparse pilosity and dark colour. It is most closely related to Monomorium subdentatum from which it is only weakly separated (see below), and to Monomorium micropacum which has about 10 pairs of hairs on the first gastral tergite and is noticeably smaller (HW 0.48, SL 0.50-0.51, PW 0.33-0.34).

Distribution based on Regional Taxon Lists
Afrotropical Region: Angola, Democratic Republic of Congo, Malawi, Uganda, Zambia, Zimbabwe.

Nomenclature

 *  opacum. Monomorium opacum Forel, 1913b: 333 (w.) DEMOCRATIC REPUBLIC OF CONGO. See also: Bolton, 1987: 353.

Worker
Bolton (1987) - TL 3.3-3.5, HL 0.80-0.86, HW 0.64-0.72, CI 80-86, SL 0.60-0.68, SI 90-100, PW 0.42-0.46, AL 0.96-1.04 (12 measured).

Anterior free margin of median portion of clypeus transverse to shallowly convex. Maximum diameter of eye 0.22-0.25 x HW, with 10-11 ommatidia in the longest row. Metanotal groove only shallowly indented. Dorsum of propodeum flattened or shallowly concave, the posteriorly divergent lateral margins of the propodeum sometimes bluntly angular. Petiole bluntly conical in profile; in dorsal view the node somewhat broader than long and approximately the same width as the postpetiole. Dorsum and sides of head, entirety of alitrunk, petiole and postpetiole sharply densely reticulate-punctate everywhere. First gastral tergite finely shagreenate. Dorsum of head behind level of frontal lobes hairless or with a single pair close to the occipital margin. Dorsal alitrunk lacking hairs. Petiole with one pair and postpetiole with 1-2 pairs of backward directed hairs. First gastral tergite with 1-2 pairs of hairs in front of the apical transverse row. If only one pair present it is at the midlength of the tergite; when a second pair also occurs it is usually between the base and the midlength of the tergite. Colour uniform medium to dark brown, the gaster usually darker in shade than the head and alitrunk.

Type Material
Bolton (1987) - Syntype workers, Zaire: Katanga ( = Shaba), Shinsenda, 10.vi.1912 (Bequaert) [examined].