Monomorium opacior

Specimen records show this to be a species that lives in semi-open areas such as acacia woodland and Bushveld.

Identification
Bolton (1987) - A member of the M. australe complex in the M. salomonis species group.

Distribution based on Regional Taxon Lists
Afrotropical Region: Botswana, Namibia, South Africa, Zimbabwe.

Nomenclature

 * . Monomorium salomonis var. opacior Forel, 1913j: 216 (in text).
 * Type-material: 10 syntype workers.
 * Type-locality: Zimbabwe (“Rhodesia”): Bulawayo, 3.xi.1912, no. 130 (G. Arnold).
 * Type-depositories: BMNH, MHNG.
 * [First available use of Monomorium salomonis r. junodi var. opacior Forel, 1913a: 136 (w.) ZIMBABWE; unavailable (infrasubspecific) name (Bolton, 1987: 352).]
 * [Misspelled as opacius by Wheeler, W.M. 1922a: 871, Ettershank, 1966: 91.]
 * Arnold, 1916: 220 (q.).
 * As unavailable (infrasubspecific) name: Santschi, 1919b: 235; Emery, 1922e: 178; Wheeler, W.M. 1922a: 871; Arnold, 1926: 231; Santschi, 1930b: 70; Santschi, 1936a: 39; Ettershank, 1966: 91.
 * Subspecies of salomonis: Arnold, 1916: 220; Stitz, 1923: 156.
 * Subspecies of subopacum: Arnold, 1944: 14.
 * Status as species: Bolton, 1995b: 265.
 * Senior synonym of opacior Bolton: Bolton, 1995b: 265.
 * Senior synonym of serenum: unpublished emendation (as both opacior and serenum syntypes examined by Bolton, 1987: 352, and judged synonymous).
 * Distribution: Botswana, South Africa, Zimbabwe.
 * opacior. Monomorium opacior Bolton, 1987: 352 (w.) ZIMBABWE, BOTSWANA, SOUTH AFRICA.
 * Type-material: 10 syntype workers.
 * Type-locality: Zimbabwe (“Rhodesia”): Bulawayo, 3.xi.1912, no. 130 (G. Arnold).
 * Type-depositories: BMNH, MHNG.
 * Junior synonym of opacior Forel: Bolton, 1995b: 265.
 * serenum. Monomorium subopacum var. serenum Arnold, 1944: 14.
 * Type-material: syntype worker(s), syntype queen(s), syntype male(s) (numbers not stated).
 * Type-locality: Zimbabwe (“Southern Rhodesia”): Bulawayo, 26.xi.1914 (G. Arnold).
 * Type-depository: NHMB.
 * [First available use of Monomorium (Xeromyrmex) delagoense st. junodi var. serenum Santschi, 1928f: 192 (w.q.m.) ZIMBABWE; unavailable (infrasubspecific) name (Bolton, 1987: 352).]
 * As unavailable (infrasubspecific) name: Santschi, 1936a: 39; Ettershank, 1966: 92.
 * Material referred to opacior by Bolton, 1987: 352.
 * Junior synonym of opacior: unpublished emendation (as both opacior and serenum syntypes examined by Bolton, 1987: 352, and judged synonymous).

Bolton (1987) - The species is described from a syntypic series as Arnold's original series are mounted flat on card and all individuals have suffered some damage and abrasion. For this reason it has not proved possible to select a holotype from the original material which exhibits all the diagnostics of the species.

Worker
Bolton (1987) - Syntype. TL 2.2-2.4, HL 0.60-0.66, HW 0.47-0.50, CI 75-78, SL 0.48-0.52, SI 100-108, PW 0.32-0.34, AL 0.68-0.74 (6 measured).

Median portion of clypeus with anterior margin transverse, sometimes appearing very slightly convex. Sides of head in full-face view almost straight, only extremely feebly convex and somewhat convergent posteriorly. Occipital margin very shallowly concave. Eyes slightly in front of the midlength of the sides of the head, the maximum eye diameter 0·24-0·26 x HW, with 8-9 ommatidia in the longest row. Metanotal groove very feebly impressed. Dorsum of head with two pairs of standing hairs behind the level of the frontal lobes, the first situated just behind the level of the eyes, the second at the occipital margin. Dorsal alitrunk without standing hairs. Petiole node without hairs, the postpetiole with a single pair which projects backward. First gastral tergite with 1-2 pairs of hairs in front of the apical transverse row, situated on the basal half of the sc1erite. Dorsum of head opaque, blanketed by fine and dense reticulate-shagreenate to punctate-shagreenate sculpture; mid-dorsally the sculpture with very fine dense longitudinal scratch-like striolae, giving the surface in this area a silky appearance. Pronotal dorsum finely reticulate to reticulate-shagreenate; posteriorly on the dorsal alitrunk the sculpture becoming more sharply reticulate or even weakly reticulate-punctate. First gastral tergite with superficial reticular patterning at least near the base, but this may fade out apically, leaving the sclerite featureless. Colour dull light brown, the gaster much darker brown and shining.

Non-partypic material. TL 2.3-2.7, HL 0.56-0.68, HW 0.43-0.52, CI 74-78, SL 0.44-0.57, SI 102-110, PW 0.30-0.35, AL 0.64-0.80 (8 measured). Maximum diameter of eye 0.25-0.27 x HW and with 8-9 ommatidia in the longest row. As syntypes but in some the first gastral tergite with 3 pairs of hairs on the basal half. Development of fine striolate component of cephalic sculpture is variable; in some individuals it is conspicuous, in others virtually absent. Also variable is the extent of the superficial reticular patterning on the first gastral tergite and the colour, which ranges from dull yellowish brown to pale medium brown. The gaster is sometimes only marginally darker than the head and alitrunk in shade.

Type Material
Bolton (1987) - Syntype workers, Zimbabwe: Bulawayo, 3.xi. 1912, no. 130 (G. Arnold) [examined].

References based on Global Ant Biodiversity Informatics

 * IZIKO South Africa Museum Collection
 * Santschi, F. "Résultats de la Mission scientifique suisse en Angola, 1928-1929. Formicides de l'Angola." Revue Suisse de Zoologie 37 (1930): 53-81.
 * Stitz H. 1923. Hymenoptera, VII. Formicidae. Beiträge zur Kenntnis der Land- und Süsswasserfauna Deutsch-Südwestafrikas 2: 143-167.