Workers forage on the forest floor and colony nests are mainly in rotten logs
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
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
Distribution based on AntMaps
Distribution based on AntWeb specimens
Check data from AntWeb
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.
The following information is derived from Barry Bolton's New General Catalogue, a catalogue of the world's ants.
- 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.
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.
Rakotonirina and Fisher (2014) - Holotype worker, Madagascar, Fort Dauphin SG (Sikora) (Musee d'Histoire Naturelle Genève) AntWeb specimen code: CASENT0101884 [examined].
- 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.