Messor tropicorum

Identification
Larger workers of tropicorum are quickly isolated by their possession of a strong prominent welt or tumulus posteromedially on the clypeus, but this character fades with reduced worker size. The eyes are quite large, approaching the lower limit of the range seen in Messor denticornis, but in the latter the propodeum is longer and lower in profile. (Bolton 1982)

Distribution based on Regional Taxon Lists
Afrotropical Region: Angola, Namibia.

Castes
Known only from the worker caste.

Nomenclature

 * . Messor capensis var. tropicorum Wheeler, W.M. 1922a: 805.
 * Type-material: syntype workers (number not stated).
 * Type-locality: Angola: Mossamedes (Baum & Van der Kellen).
 * Type-depository: MHNG.
 * [First available use of Messor barbarus subsp. capensis var. tropicorum Forel, 1910e: 444 (w.) ANGOLA; unavailable (infrasubspecific) name.]
 * As unavailable (infrasubspecific) name: Emery, 1921f: 70; Emery, 1922c: 99.
 * Subspecies of capensis: Santschi, 1930b: 55.
 * Status as species: Bolton, 1982: 354 (redescription); Bolton, 1995b: 258.
 * Senior synonym of laevifrons: Bolton, 1982: 354; Bolton, 1995b: 258.
 * Senior synonym of nigriventris: Bolton, 1982: 354; Bolton, 1995b: 258.
 * Distribution: Angola, Namibia.
 * laevifrons. Messor denticornis var. laevifrons Stitz, 1923: 148 (w.) NAMIBIA.
 * Type-material: 17 syntype workers.
 * Type-localities: 16 workers Namibia (“German Southwest Africa”): Usakos, iv.-vi.1911 (W. Michaelsen), 1 worker Namibia: Grootfontein, 7-11.vi.1911 (W. Michaelsen).
 * Type-depository: MNHU.
 * Junior synonym of tropicorum: Bolton, 1982: 354; Bolton, 1995b: 255.
 * nigriventris. Messor braunsi var. nigriventris Stitz, 1923: 150 (w.) NAMIBIA.
 * Type-material: 5 syntype workers.
 * Type-localities: 3 workers Namibia (“German Southwest Africa”): Grootfontein, 7-11.vi.1911 (W. Michaelsen), 2 workers Walvis Bay (no collector’s name).
 * Type-depository: MNHU.
 * Junior synonym of tropicorum: Bolton, 1982: 354; Bolton, 1995b: 255.

Worker
Bolton (1982) - Medium to Large, HW 3.00- > 3.80.

Anterior clypeal margin entire or at most with a feeble median indentation. With the head in full-face view the sides approximately straight, more or less parallel or feebly diverging anteriorly. Occipital margin usually broadly and shallowly concave but this becomes less apparent with decreased size. Centre of posterior half of clypeus, between the frontal lobes, with a conspicuously raised tumulus or welt in large workers, this feature decreasing in intensity with reduced size and not present in smaller workers. In the HW range 3.00-3.84 the maximum diameter of the eye is 0.64-0.72, about 0.19-0.21 x HW, and the CI range is 102-111. Propodeum in profile relatively short and high, like that of capensis. Propodeal dorsum either rounding into declivity, or meeting it in a right-angle, or armed with a pair of short triangular teeth; variation occurs within series. Dorsum of head sculptured with narrow fine longitudinal rugulae. In strongest sculptured individuals the rugulae are dense and conspicuous, but often they are much reduced or partially to entirely effaced away from the central strip. Between the rugulae the ground-sculpture is of a fine superficial punctulation, often completely effaced. Dorsal alitrunk rugulose to rugose, the sculpture frequently weak on the pronotum or even absent in places. First gastral tergite unsculptured or at most with a faint superficial reticular pattering. All dorsal surfaces of head and body with numerous conspicuous standing hairs. Head and alitrunk reddish brown, the gaster darker.

References based on Global Ant Biodiversity Informatics

 * Bolton B. 1982. Afrotropical species of the myrmicine ant genera Cardiocondyla, Leptothorax, Melissotarsus, Messor and Cataulacus (Formicidae). Bulletin of the British Museum (Natural History). Entomology 45: 307-370.
 * Forel A. 1910. Note sur quelques fourmis d'Afrique. Annales de la Société Entomologique de Belgique 54: 421-458.
 * IZIKO South Africa Museum Collection
 * Stitz H. 1923. Hymenoptera, VII. Formicidae. Beiträge zur Kenntnis der Land- und Süsswasserfauna Deutsch-Südwestafrikas 2: 143-167.