Leptogenys ridens

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).

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.

Nomenclature

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

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) AntWeb specimen code: CASENT0101884 [examined].

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): 001163.
 * 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