Nesomyrmex medusa

This species occurs in the south-western forests (Parc National de Tsimanampetsotsa, Forêt de Bemanateza and Mahafaly Plateau) of Madagascar between the southern latitudes S 24° and S 24.65°.

Identification
A member of the hafahafa species-group. The three pairs of dorsal spines (pronotal spines, propodeal spines and antero-dorsal spines on petiolar node) makes the appearance of this group extremely unique; no similar species group has been found either in the Malagasy region or on the African continent.

Distribution based on Regional Taxon Lists
Malagasy Region: Madagascar.

Nomenclature

 *  medusus. Nesomyrmex medusus Csösz & Fisher, 2015: 51, figs. 25-27 (w.q.m.) MADAGASCAR.

Worker
Body color: brown. Body color pattern: body concolorous, only clava darker. Absolute cephalic size: 1069 [958, 1189] μm (n=56). Cephalic length vs. maximum width of head capsule (CL/CWb): 1.046 [0.990, 1.097]. Postocular distance vs. cephalic length (PoOc/CL): 0.391 [0.371, 0.413]. Postocular sides of cranium contour frontal view orientation: converging posteriorly. Postocular sides of cranium contour frontal view shape: broadly convex. Vertex contour line in frontal view shape: straight; slightly concave. Vertex sculpture: main sculpture rugose, ground sculpture areolate. Gena contour line in frontal view shape: feebly convex. Genae contour from anterior view orientation: converging. Gena sculpture: rugo-reticulate with areolate ground sculpture. Concentric carinae laterally surrounding antennal foramen count: present. Eye length vs. absolute cephalic size (EL/CS): 0.232 [0.219, 0.249]. Frontal carina distance vs. absolute cephalic size (FRS/CS): 0.313 [0.295, 0.331]. Longitudinal carinae on median region of frons count: present. Longitudinal carinae on medial region of frons shape: forked. Smooth median region on frons count: absent. Antennomere count: 12. Scape length vs. absolute cephalic size (SL/CS): 0.907 [0.849, 0.997]. Facial area of the scape absolute setal angle: setae absent, pubescence only. Median clypeal notch count: present. Median clypeal notch depth vs. absolute cephalic size (Cdep/CS): 0.022 [0.017, 0.029]. Ground sculpture of submedian area of clypeus: smooth. Median carina of clypeus count: present. Lateral carinae of clypeus count: present. Median anatomical line of propodeal spine angle value to Weber length in lateral view: 65–72°. Spine length vs. absolute cephalic size (SPST/CS): 0.385 [0.333, 0.437]. Minimum spine distance vs. absolute cephalic size (SPBA/CS): 0.266 [0.234, 0.308]. Apical spine distance vs. absolute cephalic size (SPTI/CS): 0.443 [0.354, 0.504]. Propodeal spine shape: straight; slightly bent. Apical distance of pronotal spines vs. absolute cephalic size (PSTI/CS): 0.757 [0.711, 0.813]. Metanotal depression count: absent. Dorsal region of mesosoma sculpture: areolate ground sculpture, superimposed by dispersed rugae. Lateral region of pronotum sculpture: areolate ground sculpture, superimposed by dispersed rugae. Mesopleuron sculpture: areolate ground sculpture, superimposed by dispersed rugae. Metapleuron sculpture: areolate ground sculpture, superimposed by dispersed rugae. Petiole width vs. absolute cephalic size (PEW/CS): 0.268 [0.246, 0.295]. Anterodorsal spines on petiolar node angle of deviation from each other: 70°. Apical distance of anterodorsal spines on petiolar node vs. absolute cephalic size (NSTI/CS): 0.354 [0.278, 0.464]. Frontal profile of petiolar node contour line in lateral view shape: straight. Dorso-caudal petiolar profile contour line in lateral view shape: straight; convex. Dorsal region of petiole sculpture: ground sculpture areolate, main sculpture dispersed rugose; ground sculpture areolate, main sculpture absent. Postpetiole width vs. absolute cephalic size (PPW/ CS): 0.543 [0.496, 0.585]. Dorsal region of postpetiole sculpture: ground sculpture areolate, main sculpture absent; ground sculpture areolate, main sculpture dispersed rugose.

Type Material
Holotype worker. CASENT0455428, collection code: BLF06201; MADGAGASCAR: Prov. Toliara, Parc National de Tsimanampetsotsa, Mitoho Cave, 6.4 km 77° ENE Efoetse, 17.4 km 170°S Beheloka, 24°03'S, 43°46'E [-24.04722 N, 43.75317 E], 65 m, 18–22.iii.2002 Fisher et al. ; Paratypes. Ten workers, a single gyne and two males with the same label data as the holotype (CAS).

Etymology
The numerous long spines on the dorsal body make the workers reminiscent of Medusa of the Greek mythology who has snakes on her head in place of hair.

References based on Global Ant Biodiversity Informatics

 * Csosz S., and B. L. Fisher. 2015. Diagnostic survey of Malagasy Nesomyrmex species-groups and revision of hafahafa group species via morphology based cluster delimitation protocol. ZooKeys 526: 19–59.