Nesomyrmex exiguus

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Nesomyrmex exiguus
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Myrmicinae
Tribe: Crematogastrini
Genus: Nesomyrmex
Species group: angulatus
Species: N. exiguus
Binomial name
Nesomyrmex exiguus
Csösz & Fisher, 2016

Nesomyrmex exiguus casent0077581 p 1 high.jpg

Nesomyrmex exiguus casent0077581 d 1 high.jpg

Specimen Labels

This species is endemic to the Malagasy region, and its distribution is restricted to the northern, dry area of Madagascar. There it lives in littoral rainforest and tropical dry forest; a single locality (Forêt d' Andavakoera) is known in rainforest close to other known localities of this species in the northern, dry bioclimatic zone.

Identification

Csősz and Fisher (2016) - A member of the angulatus species-group. Workers of N. exiguus differ from those of Nesomyrmex clypeatus by having no median clypeal notch and from those of Nesomyrmex angulatus by the lack of anterolateral pronotal corner. No single ratio separates this species from Nesomyrmex bidentatus and Nesomyrmex fragilis, but a combined application of two morphometric ratios (PPW/ML and CW/SPST) provides a safe opportunity for separation. This species occurs in the northern part of Madagascar syntopically with Nesomyrmex gracilis from the Nesomyrmex devius complex. A simple ratio (PoOC/SPTI, see details in key) offers 94.5% success discriminating between this species and N. gracilis, 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 these are distributed far south of the distributional area of N. exiguus.

Keys including this Species

Distribution

Distribution based on Regional Taxon Lists

Malagasy Region: Madagascar (type locality).


Distribution based on AntMaps

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Distribution based on AntWeb specimens

Check data from AntWeb

Biology

Csősz and Fisher (2016) - Two samples that may raise the chance of misclassifications are known to have been collected in far southern localities. These samples were classified as N. exiguus by cumulative LDA with very high posterior probabilities (CASENT0208857, p D 0:971 and CASENT0496931, p D 0:998) when these were added as wildcards to minimize the chance of possible misclassifications. These individuals are most probably representatives of populations brought to these localities by people.

Castes

Worker

Queen

Nomenclature

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

  • exiguus. Nesomyrmex exiguus Csösz & Fisher, 2016: 23, figs. 10A-10C (w.q.m.) MADAGASCAR.

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

Description

Worker

Body color: yellow; brown. Body color pattern: concolorous. Absolute cephalic size (mm): 586 [528, 644] (n D 84). Cephalic length vs. maximum width of head capsule (CL/CWb): 1.213 [1.174, 1.255]. Postocular distance vs. cephalic length (PoOc/CL): 0.408 [0.391, 0.428]. 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): 0.249 [0.228, 0.266]. Frontal carina distance vs. absolute cephalic size (FRS/CS): 0.413 [0.397, 0.431]. 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): 0.656 [0.615, 0.683]. 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: 27-32°. Spine length vs. absolute cephalic size (SPST/CS): 0.382 [0.317, 0.430]. Minimum spine distance vs. absolute cephalic size (SPBA/CS): 0.390 [0.352, 0.454]. Apical spine distance vs. absolute cephalic size (SPTI/CS): 0.436 [0.377, 0.493]. Propodeal spine shape: straight; slightly bent. Anterolateral pronotal corner: absent. Metanotal depression count: 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): 0.437 [0.387, 0.480]. Dorsal region of petiole sculpture: ground sculpture areolate, main sculpture dispersed rugose. Postpetiole width vs. absolute cephalic size (PPW/CS): 0.516 [0.481, 0.548]. Dorsal region of postpetiole sculpture: ground sculpture areolate, main sculpture dispersed rugose.

Type Material

Holotype worker: Madagascar: Prov. Antsiranana, Fort Antsahabe, 11.4 km 275° W Daraina, 13° 13:7’S, 49° 33:4’E, 550 m, 12-14.xii.2003, collection code: BLF10161; CASENT0077581, Fisher et al. (CASENT0077581, California Academy of Sciences). Paratypes: seventeen workers, a single gyne and a male with the same locality data (CASC).

Etymology

This name exiguus (Dstrict, exact) refers to the fact that this species is relatively easily to distinguish.

References

  • Csosz, S. & Fisher, B.L. 2016. Taxonomic revision of the Malagasy members of the Nesomyrmex angulatus species group using the automated morphological species delineation protocol NC-PART-clustering. PeerJ 4:e1796 doi:10.7717/peerj.1796