Leptogenys ridens

Leptogenys ridens
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Insecta
Order:	Hymenoptera
Family:	Formicidae
Subfamily:	Ponerinae
Tribe:	Ponerini
Genus:	Leptogenys
Species:	L. ridens
Binomial name
	Leptogenys ridens; Forel, 1910 Specimen Labels

Workers forage on the forest floor and colony nests are mainly in rotten logs

Identification

A member of the ridens complex of the truncatirostris species group. Rakotonirina and Fisher (2014) - Worker. Clypeus with median carina, long median lobe, distance between anterior level of torulus and anteromedial clypeal margin greater than maximum width of scape; antennal scape relatively long, more than one third of its length surpassing posterior cephalic margin; eye larger, maximum diameter twice as large as maximum width of antennal scape.

Leptogenys ridens is larger in size and has a relatively longer antennal scape (SI: 122–129) and larger eyes when compared to very similar species such as Leptogenys fotsivava, Leptogenys namoroka and Leptogenys tsingy. In the latter three species, the maximum diameter of the eye is less than twice the maximum scape width, and the scape is relatively shorter (SI: 111–120).

Keys including this Species

Key to Malagasy Leptogenys

Distribution

Leptogenys ridens is restricted to the south of Madagascar. It occurs from the tropical dry forests in the southwest, through the spiny forest/thicket of Mahafaly Plateau and the extreme south, and to the gallery forest of RP Berenty in the southeast.

Distribution based on Regional Taxon Lists

Malagasy Region: Madagascar (type locality).

Distribution based on AntMaps

Distribution based on AntWeb specimens

Check data from AntWeb

Countries Occupied

Number of countries occupied by this species based on AntWiki Regional Taxon Lists. In general, fewer countries occupied indicates a narrower range, while more countries indicates a more widespread species.

Estimated Abundance

Relative abundance based on number of AntMaps records per species (this species within the purple bar). Fewer records (to the left) indicates a less abundant/encountered species while more records (to the right) indicates more abundant/encountered species.

Biology

Explore Overview of MalLeptogenys biology

The Leptogenys genus page has more details about the general biology of ants in this genus. The following synopsis provided by Rakotonirina and Fisher (2014) offers an overview of the Malagasy Leptogenys: Recent surveys of arthropods in the Malagasy region uncovered a wealth of new species and showed that Leptogenys is one of the dominant ponerine ants widely distributed across all types of forest habitats. Workers are usually found foraging on the forest floor or in the leaf litter and only rarely on vegetation. They nest terrestrially under the soil, rocks, logs, or rootmat ground layers and in rotten logs, branches, in rotting bamboo, and rotten tree stumps. Most of the Malagasy species are endemic to Madagascar. In all Malagasy species, winged queens are absent, which limits their ability to disperse across the complex topography and various ecological barriers in the region. In the absence of alate queens, reproduction of Leptogenys in the region may be by fission, which enhances population viscosity and may result in important morphological variation across a species' geographic range. Though queens do not fly, males of Leptogenys are alate and are one of the most frequently collected ant genera in Malaise traps throughout Madagascar. Leptogenys exhibits a wide range of phenotypic diversity segregated both among spatially isolated habitats and along continuous environmental gradients.

Castes

Worker

Images from AntWeb


Holotype of Leptogenys ridens. Worker. Specimen code casent0101884. Photographer April Nobile, uploaded by California Academy of Sciences.	Owned by MHNG, Geneva, Switzerland.

Nomenclature

The following information is derived from Barry Bolton's Online Catalogue of the Ants of the World.

ridens. Leptogenys ridens Forel, 1910a: 16 (w.) MADAGASCAR. Combination in L. (Machaerogenys): Emery, 1911d: 100. See also: Bolton, 1975a: 295.

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

Description

Worker

Rakotonirina and Fisher (2014) - (8 specimens). HW: 1.29–1.59, HL: 1.50–1.76, CI: 86–92, SL: 1.67–1.99, SI: 122–129, PW: 0.92–1.11, WL: 2.49–2.92, PNH: 0.84–1.01, PNL: 0.67–0.81, PNW: 0.75–0.91, DNI: 106–117, LNI: 115–128.

Head elongate and distinctly broadened anteriorly; sides noticeably diverging in front of eyes and curving into roughly straight posterior border. Eye large, maximum diameter twice as large as widest portion of antennal scape, or about one-third of length of lateral cephalic margin; eye girth not cutting lateral outline of head in full-face view. Scape relatively long (SI: 122–129), more than one third of the length surpassing posterior cephalic margin. Clypeus with medial longitudinal carina; broadly rounded anterior margin trimmed by white-yellowish membrane; median lobe relatively elongate, length between anterior level of antennal insertion and anteromedial clypeal margin greater than maximum diameter of scape when head in full-face view. In full-face view, apical third of mandible not following shape of anterior clypeal margin when tightly closed against clypeus, but projected anteriorly and crossing each other in front of anteromedial clypeal margin. With mesosoma in dorsal view, metanotal groove impressed and cross-ribbed; in profile propodeal lobe indistinct. Petiole nodiform in lateral view, convex dorsal border broadly rounding to vertical anterior margin and joining the slightly medially convex posterior margin in a convex line. Mandible longitudianally striate, interspersed with piligerous punctures. Dorsum of head densely and finely reticulate-punctate. Mesosoma finely reticulate-rugose to densely and finely punctate. Dorsum of petiolar node and third abdominal tergite finely punctate; sparse punctures present on their sides. Suberect hairs short, pubescence abundant. Black in color, with reddish-brown apices of appendages and apex of gaster.

Type Material

Rakotonirina and Fisher (2014) - Holotype worker, Madagascar, Fort Dauphin SG (Sikora) (Musee d'Histoire Naturelle Genève) AntWeb specimen code: CASENT0101884 [examined].

References

Bolton, B. 1975a. A revision of the ant genus Leptogenys Roger (Hymenoptera: Formicidae) in the Ethiopian region with a review of the Malagasy species. Bull. Br. Mus. (Nat. Hist.) Entomol. 31: 235-305 (page 295, see also)
Emery, C. 1911e. Hymenoptera. Fam. Formicidae. Subfam. Ponerinae. Genera Insectorum 118: 1-125 (page 100, Combination in L. (Machaerogenys))
Forel, A. 1910a. Glanures myrmécologiques. Ann. Soc. Entomol. Belg. 54: 6-32 (page 16, worker described)
Rakotonirina, J.C. & Fisher, B.L. 2014. Revision of the Malagasy ponerine ants of the genus Leptogenys Roger (Hymenoptera: Formicidae). Zootaxa 3836, 1-163.

References based on Global Ant Biodiversity Informatics

Fisher B. L. 1997. Biogeography and ecology of the ant fauna of Madagascar (Hymenoptera: Formicidae). Journal of Natural History 31: 269-302.
Fisher B. L. 2003. Formicidae, ants. Pp. 811-819 in: Goodman, S. M.; Benstead, J. P. (eds.) 2003. The natural history of Madagascar. Chicago: University of Chicago Press, xxi + 1709 pp.
Rakotonirina J. C., and B. L. Fisher. 2014. Revision of the Malagasy ponerine ants of the genus Leptogenys Roger (Hymenoptera: Formicidae). Zootaxa 3836 (1): 001163.
Wheeler W. M. 1922. 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. Bulletin of the American Museum of Natural History 45: 1005-1055