Ocymyrmex robustior

Chance observation by Marsh in the Namib Desert indicates that mating almost definitely occurs at night, probably at almost any time of the year, and takes place at the nest entrance of the mother colony. Their main food supply is obtained by scavenging dead or heat-stressed insects. (Bolton and Marsh 1989).

Identification
A member of the  barbiger group.

Distribution based on Regional Taxon Lists
Afrotropical Region: Namibia.

Biology
In O. robustior, the mean number of workers plus ergatoid queens per nest ± SD was 347.6 ± 170.5 (N = 20). The proportion of ergatoid queens per nest ranged from 0 to 26%, averaging 14.5% (Lecocq de Pletincx et al. 2019). There is only one mated egg-laying ergatoid queen in each colony, and all the others behave like the worker caste. This fits the definition of "multi-purpose ergatoid queens" already studied in Eutetramorium mocquerysi (Myrmicinae) and Mystrium voeltzkowi (Amblyoponinae).

A series of papers focused on Ocymyrmex biology (Marsh, 1985 a, 1985 b), or on Ocymyrmex species as a component of the Namib Desert ant community (Marsh, 1985 c, 1986 a, 1986 b) included information about robustior. In all but the last of these papers the ant referred to as Ocymyrmex barbiger is actually Ocymyrmex robustior. At the times of publication of Marsh's first four papers robustior was incorrectly being treated as a junior synonym of barbiger. The former is now considered to be a valid species, separate from barbiger but belonging to the same species-group. The name robustior was elevated to species-level in Marsh (1986 b).

Nomenclature

 *  robustior. Ocymyrmex barbiger var. robustior Stitz, 1923: 146 (w.) NAMIBIA. Bolton & Marsh, 1989: 1279 (q.m.). Junior synonym of barbiger: Bolton, 1981b: 265. Revived from synonymy and raised to species: Marsh, 1986: 339. See also: Marsh, 1985: 286; Bolton & Marsh, 1989: 1303.

References based on Global Ant Biodiversity Informatics

 * Bolton B., and A. C. Marsh. 1989. The Afrotropical thermophilic ant genus Ocymyrmex (Hymenoptera: Formicidae). Journal of Natural History 23: 1267-1308.
 * Campbell H., M. D. E. Fellowes, and J. M. Cook. . Species diversity and dominance-richness relationships for ground and arboreal ant (Hymenoptera: Formicidae) assemblages in Namibian desert, saltpan, and savannah. Myrmecological News 21: 37-47.
 * IZIKO South Africa Museum Collection
 * Lecocq de Pletincx, A. Kuhn, and S. Aron. 2019. Population structure and sociogenetic organisation in a species with ergatoid queens, the desert ant Ocymyrmex robustior. https://doi.org/10.1007/s00040-019-00697-w
 * Marsh A. C. 1986. Checklist, biological notes and distribution of ants in the central Namib Desert. Madoqua 14: 333-344.
 * Stitz H. 1923. Hymenoptera, VII. Formicidae. Beiträge zur Kenntnis der Land- und Süsswasserfauna Deutsch-Südwestafrikas 2: 143-167.