Nesomyrmex gracilis

This species is endemic to the Malagasy region, and its distribution is restricted to the northern, dry area of Madagascar in various habitats: rainforests, rainforest edges, littoral forests, and tropical dry forests.

Identification
Csősz and Fisher (2016) - A member of the angulatus species-group. Workers of N. gracilis differ from those of Nesomyrmex clypeatus by having no median clypeal notch and from Nesomyrmex angulatus by the lack of an anterolateral pronotal corner. This species can be separated from Nesomyrmex bidentatus and Nesomyrmex fragilis based on the apical spine distance ratio (SPTI/CS). This species occurs in the northern part of Madagascar syntopically with Nesomyrmex exiguus from the Nesomyrmex devius complex. A simple ratio (PoOC/SPTI, see details in key) offers 94.5% success in distinguishing between this species and N. exiguus, and a combination of two ratios (PoOC/SPTI and CWb/ML) yields a safe determination. The other two species of this complex, N. devius and Nesomyrmex hirtellus, do not occur syntopically with this species, as both are distributed far south of the range of N. gracilis.

Distribution based on Regional Taxon Lists
Malagasy Region: Madagascar.

Nomenclature

 *  gracilis. Nesomyrmex gracilis Csösz & Fisher, 2016: 27, figs. 12A-12C (w.q.m.) MADAGASCAR.

Worker
Body color: yellow; brown. Body color pattern: concolorous. Absolute cephalic size (mm): 620 [508, 699], (n D 44). Cephalic length vs. maximum width of head capsule (CL/CWb): 1.199 [1.154, 1.246]. Postocular distance vs. cephalic length (PoOc/CL): 0.387 [0.372, 0.406]. Postocular sides of cranium contour frontal view orientation: parallel; converging anteriorly. Postocular sides of cranium contour frontal view shape: straight; feebly convex; convex. Vertex contour line in frontal view shape: straight; feebly convex. Vertex sculpture: main sculpture rugose, ground sculpture areolate. Gena contour line in frontal view shape: convex. Genae contour from anterior view orientation: converging; strongly converging. Gena sculpture: rugoso-reticulate with areolate ground sculpture. Concentric carinae laterally surrounding antennal foramen: absent. Eye length vs. absolute cephalic size (EL/CS): 0.252 [0.228, 0.274]. Frontal carina distance vs. absolute cephalic size (FRS/CS): 0.413 [0.390, 0.436]. Longitudinal carinae on median region of frons: absent. Smooth median region on frons: absent. Antennomere count: 12. Scape length vs. absolute cephalic size (SL/CS): 0.647 [0.622, 0.685]. Facial area of the scape absolute setal angle: 0-15°. Median clypeal notch: absent. Ground sculpture of submedian area of clypeus: present. Median carina of clypeus: present. Lateral carinae of clypeus: present. Median anatomical line of propodeal spine angle value to Weber length in lateral view: 40-45°. Spine length vs. absolute cephalic size (SPST/CS): 0.399 [0.301, 0.446]. Minimum spine distance vs. absolute cephalic size (SPBA/CS): 0.393 [0.350, 0.433]. Apical spine distance vs. absolute cephalic size (SPTI/CS): 0.489 [0.448, 0.536]. Propodeal spine shape: straight; slightly bent. Anterolateral pronotal corner: absent. Metanotal depression: present. Dorsal region of mesosoma sculpture: rugulose with areolate ground sculpture. Lateral region of pronotum sculpture: areolate ground sculpture, superimposed by dispersed rugae. Mesopleuron sculpture: areolate ground sculpture superimposed by dispersed rugulae. Metapleuron sculpture: areolate ground sculpture superimposed by dispersed rugulae. Petiole width vs. absolute cephalic size (PEW/CS): 0.454 [0.390, 0.487]. Dorsal region of petiole sculpture: ground sculpture areolate, main sculpture dispersed rugose. Postpetiole width vs. absolute cephalic size (PPW/CS): 0.500 [0.453, 0.539]. Dorsal region of postpetiole sculpture: ground sculpture areolate, main sculpture dispersed rugose.

Type Material
Holotype worker: Madagascar: Prov. Antsiranana, Forêt Ambato, 26.6 km 33° Ambanja, 13° 27:87’S, 48° 33:10’E, 150 m, 8-11.xii.2004, collection code: BLF11548; CASENT0107191, Fisher et al. (CASENT0107191, ). Paratypes: three workers, three gynes, and a male with the same locality data. (CASC).

Etymology
This name gracilis (=slender, slim) refers to the small, tiny appearance of this species.