Nesomyrmex madecassus

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Nesomyrmex madecassus
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Myrmicinae
Tribe: Crematogastrini
Genus: Nesomyrmex
Species group: madecassus
Species: N. madecassus
Binomial name
Nesomyrmex madecassus
(Forel, 1892)

Nesomyrmex madecassus casent0487142 profile 1.jpg

Nesomyrmex madecassus casent0487142 dorsal 1.jpg

Specimen labels

This species is known to occur in Madagascar’s rain forests at very high altitudes between 690 and 2150m, mean: 1538m. This species is known to forage in low vegetation, nests can often be found in dead twigs, or rarely 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 this species differ from that of Nesomyrmex gibber by having no mesothoracic hump, and from Nesomyrmex flavus and Nesomyrmex nitidus by its dark brown color versus the light yellow hue of the two latter species.

The dark color in madecassus populations is dominant across the entire known distributional area, and comprises ~95% of the examined material. However, a rare, lighter-colored madecassus phenotype (ocher phenotype) was also found in a few localities. There is no evidence, other than color, that would support heterospecifity of these two discrete phenotypes of N. madecassus workers and no correlation was found between elevational cline and color. Only one mixed sample is known to include both ocher and dark phenotype. Ocher madecassus phenotypes are darker than the majority of N. flavus and N. nitidus workers and also differ from the latter species by having brown femora and a dark patch on the first gastral tergite.

Nesomyrmex madecassus workers (including ocher phenotypes) can be separated from those of N. flavus and N. nitidus using a ratio of postocular area to cephalic width including compound eyes (PoOC/CW). A more precise means to separate ocher madecassus phenotype from workers of N. flavus and N. nitidus may be necessary. In these cases, a discriminant D4 funtion provides a moderately time consuming classification tool yielding non-overlapping ranges between madecassus workers and that of flavus and nitidus.

Keys including this Species

Distribution

Distribution based on Regional Taxon Lists

Afrotropical Region: Comoros.
Malagasy Region: Madagascar (type locality), Mayotte.


Distribution based on AntMaps

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Distribution based on AntWeb specimens

Check data from AntWeb

Biology

Castes

Worker

Queen

Male

Nomenclature

The following information is derived from Barry Bolton's New General Catalogue, a catalogue of the world's ants.

  • madecassus. Leptothorax madecassus Forel, 1892l: 265 (w.q.) MADAGASCAR.
    • Combination in L. (Goniothorax): Emery, 1896g: 58 (footnote).
    • Combination in Nesomyrmex: Bolton, 2003: 272.
    • Status as species: Csősz & Fisher, 2016: 120.

Unless otherwise noted the text for the remainder of this section is reported from the publication that includes the original description.

Description

Worker

Csősz & Fisher (2016) - Body color: brown; black; rarely yellow. Body color pattern: Body concolorous. If yellow, body concolorous, clava, femora and 1st gastral tergite darker. Absolute cephalic size: 692 [616, 763]. Cephalic length vs. Maximum width of head capsule (CL/CWb): 1.18 [1.13, 1.22]. Postocular distance vs. cephalic length (PoOc/CL): 0.46 [0.43, 0.48]. 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 inconspuous, ground sculpture smooth. Gena contour line in frontal view shape: convex. Genae contour from anterior view orientation: converging. Gena sculpture: rugoso-reticulate with feeble areolate ground sculpture. Concentric carinae laterally surrounding antennal foramen: present. Eye length vs. absolute cephalic size (EL/CS): 0.26 [0.24, 0.28]. Frontal carina distance vs. absolute cephalic size (FRS/CS): 0.31 [0.29, 0.33]. 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): 0.78 [0.72, 0.82]. 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: areolate ground sculpture, superimposed by dispersed rugae. Lateral region of pronotum sculpture: areolate ground sculpture, main sculpture dispersed costate. Mesopleuron sculpture: ground sculpture areolate, main sculpture absent. Metapleuron sculpture: ground sculpture areolate, main sculpture absent. Petiole width vs. absolute cephalic size (PEW/CS): 0.22 [0.19, 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. Dorsal region of petiole sculpture: ground sculpture areolate, main sculpture absent. Postpetiole width vs. absolute cephalic size (PPW/CS): 0.35 [0.29, 0.39]. Dorsal region of postpetiole sculpture: ground sculpture areolate, main sculpture absent.

Type Material

Csősz & Fisher (2016) - Syntype workers: CASENT0101667, (collection code: ANTC3246), CASENT0101687 (collection code: ANTC3247): [Madagascar, Prov.] Antsiranana, Forêt d’ Andrangoloaka [Antananarivo, -18.91 N, 47.55 E], Madagascar (Sikora)”, (CASENT0101667, CASENT0101687, Musee d'Histoire Naturelle Genève).

References

  • Bolton, B. 2003. Synopsis and Classification of Formicidae. Mem. Am. Entomol. Inst. 71: 370pp (page 272, Combination in Nesomyrmex)
  • Csősz, S.; Fisher, B. L. 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).
  • Emery, C. 1896g. Studi sulle formiche della fauna neotropica. XVII-XXV. Bull. Soc. Entomol. Ital. 28: 33-107 (page 58, Combination in L. (Goniothorax))
  • Fisher, B. L. 1997a. Biogeography and ecology of the ant fauna of Madagascar (Hymenoptera: Formicidae). J. Nat. Hist. 31: 269-302 (see also)
  • Forel, A. 1892o. Les Formicides. [concl.]. In: Grandidier, A. Histoire physique, naturelle, et politique de Madagascar. Volume XX. Histoire naturelle des Hyménoptères. Deuxième partie. Supplèment au 28e fascicule. Paris: Hachette et Cie, pp. 229-280. (page 265, worker, queen described)
  • Wheeler, W. M. 1922k. Ants of the American Museum Congo expedition. A contribution to the myrmecology of Africa. IX. A synonymic list of the ants of the Malagasy region. Bull. Am. Mus. Nat. Hist. 4 45: 1005-1055 (see also)