Nesomyrmex flavus

This species is known to occur in Madagascar’s rain forests at high altitudes between 200 and 1755m, mean: 1190m. This species is known to forage in low vegetation and nests can often be found in dead twigs. This species has occasionally been collected in leaf litter (leaf mold, rotten wood), or in rotten tree stumps.

Identification
A member of the madecassus species-group.

Csősz & Fisher (2016) - Workers of N. flavus cannot be confused with Nesomyrmex gibber because the conspicuous mesothoracic hump which is a diagnostic character of the latter species is absent in N. flavus workers. This species can be easily separated from dark phenotypes of Nesomyrmex madecassus by color: the dark madecassus phenotypes are dark brown but the workers of N. flavus are light yellow. Morphometric ratio (PoOC/CW) and discriminant D4 function helps to separate N. flavus from ocher madecassus phenotypes.

The workers of this species are the most similar to that of Nesomyrmex nitidus. The elevational distribution of the two species may provide hints useful for separation but the ranges broadly overlap. These taxa represent true cryptic species which cannot be identified based on qualitative characters (i.e. sculpture, shape or color), and their overlapping range means ratios cannot be used for identification. Therefore, only a discriminant D2 function with a greatly reduced character set yields complete separation.

Distribution based on Regional Taxon Lists
Malagasy Region: Madagascar.

Nomenclature

 *  flavus. Nesomyrmex flavus Csősz & Fisher, 2016: 115, figs. 4-6 (w.q.m.) MADAGASCAR.

Worker
Body color: yellow. Body color pattern: Body concolorous. Absolute cephalic size: 602 [533, 699]. Cephalic length vs. Maximum width of head capsule (CL/CWb): 1.26 [1.19, 1.36]. Postocular distance vs. cephalic length (PoOc/ CL): 0.48 [0.46, 0.50]. 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 inconspicuous, ground sculpture smooth. Gena contour line in frontal view shape: convex. Genae contour from anterior view orientation: converging; strongly converging. Gena sculpture: Concentric carinae laterally surrounding antennal foramen: present. Eye length vs. absolute cephalic size (EL/CS): 0.25 [0.23, 0.27]. Frontal carina distance vs. absolute cephalic size (FRS/CS): 0.30 [0.28, 0.32]. Longitudinal carinae on median region of frons: present. Longitudinal carinae on medial region of frons shape: variable. Smooth median region on frons: present. Antennomere count: 12. Scape length vs. absolute cephalic size (SL/CS): 0.80 [0.76, 0.83]. Median clypeal notch: variable. Ground sculpture of submedian area of clypeus: present. Median carina of clypeus: absent. Lateral carinae of clypeus: present. Metanotal depression: variable. Dorsal region of mesosoma sculpture: fine areolate ground sculpture, superimposed by dispersed rugae. Lateral region of pronotum sculpture: areolate ground sculpture, main sculpture dispersed costate. Mesopleuron sculpture: fine areolate ground sculpture, superimposed by dispersed rugulae. Metapleuron sculpture: fine areolate ground sculpture, superimposed by dispersed rugulae. Petiole width vs. absolute cephalic size (PEW/ CS): 0.22 [0.21, 0.24]. Anterior profile of petiolar node contour line in lateral view shape: concave. Dorso-caudal petiolar profile contour line in lateral view shape: convex; strongly convex. Dorsal region of petiole sculpture: ground sculpture smooth, main sculpture absent. Postpetiole width vs. absolute cephalic size (PPW/CS): 0.35 [0.33, 0.40]. Dorsal region of postpetiole sculpture: ground sculpture smooth, main sculpture dispersed rugose; ground sculpture smooth, main sculpture absent.

Type Material
Holotype: CASENT0393113, collection code: BLF36563: Madagascar, Prov. Toliara, Anosy Region, Anosyenne Mts, 31.2 km NW Manantenina, N -24.13894, E 47.06804, alt 1125 m, B.L. Fisher, F.A. Esteves et al., 2_26_2015, (1w, ). Paratypes: Five workers, four gynes and two males with the same label data with the holotype under CASENT codes: CASENT0393110, collection code: BLF36563 (1w, 1q, CASC); CASENT0393111, collection code: BLF36563 (1w, 1q, CASC); CA-SENT0393112, collection code: BLF36563 (1w, 1q, CASC); CASENT0393113, col-lection code: BLF36563 (1q, CASC); CASENT0393114, collection code: BLF36563 (1w, 1m, CASC); CASENT0393115, collection code: BLF36563 (1w, 1m, CASC)