Nesomyrmex gibber

Endemic to Mauritius island. Occur in rainforests higher altitude between 500 and 800 meters, (mean = 714 m). This species can be collected on low vegetation and in dead stems.

Identification
A member of the madecassus species-group. Csősz & Fisher (2016) - This species is easily distinguished from all others in the group by the conspicuous mesothoracic hump on the mesosoma of workers.

Distribution based on Regional Taxon Lists
Malagasy Region: Madagascar, Mauritius.

Nomenclature

 *  gibber. Ireneopone gibber Donisthorpe, 1946d: 242, figs. 1, 2 (w.) MAURITIUS.
 * Combination in Nesomyrmex: Bolton, 2003: 272.
 * Status as species: Csősz & Fisher, 2016: 118.

Worker
Csősz & Fisher (2016) - Body color: brown. Body color pattern: Body concolorous. Absolute cephalic size: 724 [655, 752]. Cephalic length vs. Maximum width of head capsule (CL/CWb): 1.17 [1.14, 1.18]. Postocular distance vs. cephalic length (PoOc/ CL): 0.41 [0.39, 0.42]. Postocular sides of cranium contour frontal view orientation: converging posteriorly. Postocular sides of cranium contour frontal view shape: convex. Vertex contour line in frontal view shape: straight; slightly concave. Vertex sculpture: main sculpture absent, ground sculpture areolate. Gena contour line in frontal view shape: convex. Genae contour from anterior view orientation: converging; strongly converging. Gena sculpture: ground sculpture areolate, main sculpture absent. Concentric carinae laterally surrounding antennal foramen: absent. Eye length vs. absolute cephalic size (EL/CS): 0.25 [0.24, 0.26]. Frontal carina distance vs. absolute cephalic size (FRS/ CS): 0.33 [0.32, 0.34]. Longitudinal carinae on median region of frons: absent. Smooth median region on frons: present. Antennomere count: 12. Scape length vs. absolute cephalic size (SL/CS): 0.80 [0.78, 0.82]. Median clypeal notch: present. Ground sculpture of submedian area of clypeus: present. Median carina of clypeus: absent. Lateral carinae of clypeus: absent. Metanotal depression: present. Dorsal region of mesosoma sculpture: ground sculpture areolate, main sculpture absent. Lateral region of pronotum sculpture: ground sculpture areolate, main sculpture absent. Mesopleuron sculpture: ground sculpture areolate, main sculpture absent. Metapleuron sculpture: ground sculpture areolate, main sculpture absent. Petiole width vs. absolute cephalic size (PEW/CS): 0.21 [0.20, 0.23]. Anterior profile of petiolar node contour line in lateral view shape: concave. Dorso-caudal petiolar profile contour line in lateral view shape: strongly convex. Dorsal region of petiole sculpture: ground sculpture areolate, main sculpture absent. Postpetiole width vs. absolute cephalic size (PPW/CS): 0.30 [0.27, 0.32]. Dorsal region of postpetiole sculpture: ground sculpture areolate, main sculpture absent.

Type Material
Csősz & Fisher (2016) - Holotype: “Ireneopone gibber, H. Donistorphe, 1946 TYPE” Mauritius, Calebasses Mt., 22. X. 1944, No 72 leg. R. Mamet (1w,, London, U.K., CASENT0102303), [type specimen was morphometrically not investigated, AntWeb images were used for comparison].

References based on Global Ant Biodiversity Informatics

 * Bolton B. 1976. The ant tribe Tetramoriini (Hymenoptera: Formicidae). Constituent genera, review of smaller genera and revision of Triglyphothrix Forel. Bulletin of the British Museum (Natural History). Entomology 34:281-379.
 * Csosz S. and B. L. Fisher. 2016. Taxonomic revision of the Malagasy Nesomyrmex madecassus species-group using a quantitative morphometric approach. ZooKeys 603: 105–130. doi: 10.3897/zookeys.603.8271
 * Donisthorpe H. 1946. Ireneopone gibber (Hym., Formicidae), a new genus and species of myrmicine ant from Mauritius. Entomologist's Monthly Magazine 82: 242-243.
 * Donisthorpe, Horace. 1946. The Ants (Hym. Formicidae) of Mauritius. Annals and Magazine of National History. Ser. 11. 13:25-35.
 * Fisher B. L. 1997. Biogeography and ecology of the ant fauna of Madagascar (Hymenoptera: Formicidae). Journal of Natural History 31: 269-302.
 * Fisher B. L. 2005. A new species of Discothyrea Roger from Mauritius and a new species of Proceratium Roger from Madagascar (Hymenoptera: Formicidae). Proceedings of the California Academy of Sciences (4)56: 657-667.