Leptogenys gracilis

This species has been observed foraging on the ground and nests are known from rotten logs.

Identification
A member of the imerinensis complex of the incisa species group. Rakotonirina and Fisher (2014) - Worker. Two peg-like setae projecting anteriorly from near anterior margin of median lobe of clypeus; translucent lamella of clypeus forming three distinct angles anteriorly; median longitudinal clypeal carina sharp; antennal scape relatively short (SI: 107–121), less than one fourth its length extending beyond posterior margin of head; additional suture present between metanotal groove and propodeum, thus in dorsal view, four divisions present on mesosoma, mandible striate, interspersed with punctures.

Leptogenys gracilis can be confounded with Leptogenys suarensis but has generally striate mandibles and two peg-like setae projecting above the triangular translucent lamella of the anteromedian margin of the clypeus, whereas the latter possesses generally smooth and shining mandible and three to four peg-like setae anteriorly projecting above the broadly rounded fringing lamella of the anteromedian margin of the clypeus. In the Malagasy region, L. gracilis is distributed in distantly isolated areas, and the disjunct populations vary in morphology. Populations differ in the length of petiolar node, the width of the fringing lamella on the anterior clypeal margin, and the abundance of erect hairs and pubescence. This diversity is currently considered intraspecific geographical variation.

Distribution
Leptogenys gracilis is distributed generally in northeastern Madagascar where it occupies littoral and lowland rainforests at altitudes between 3 m and 50 m. Worker specimens have also been collected from the transitional humid forest of Ambilanivy in the Ampasindava peninsula and from montane forest on Mohéli Island, The Comoros.

Distribution based on Regional Taxon Lists
Afrotropical Region: Comoros. Malagasy Region: Madagascar.

Nomenclature

 *  gracilis. Leptogenys gracilis Emery, 1899f: 271 (w.) MADAGASCAR.

Worker
Rakotonirina and Fisher (2014) - (7 specimens). HW: 0.96–1.13, HL: 1.17–1.32, CI: 82–87, SL: 1.09–1.32, SI: 107–121, PW: 0.81–0.91, WL: 1.99–2.31, PNH: 0.65–0.72, PNL: 0.61–0.79, PNW: 0.63–0.74, DNI: 86–108, LNI: 87–109.

Head roughly longer than broad, slightly broader in front of eye than at the back; lateral margin broadly convex and feebly diverging; posterior margin slightly concave medially. Eye large and protruding; exceeding line of lateral cephalic border when head in full-face view. Antennal scape short, approximately only one-fourth of its length reaching posterior margin of head. Clypeus broadly triangular; lateral margin slightly convex with obtusely angulate anteromedian border fringed by continuous translucent lamella; near border of anteromedian lobe with pair of anteriorly projecting peg-like setae; median clypeal carina sharp. Mandible elongate and slender, inner margin with slightly blunt angle near base and weakly concave towards apex; basal groove vestigial to almost effaced; preapical denticle present close to apical tooth. Hypostomal teeth short and not visible in full-face view of head. Metanotal groove impressed; in dorsal view, mesosoma with four visible segments, an additional suture present between metanotal groove and propodeum; propodeum unarmed. With petiole in dorsal view, node either as long as or longer than broad; in lateral view, dorsal border convex and forming blunt angle with vertical anterior face and forward sloping posterior face. Constriction visible between abdominal segments III and IV. Mandible most often longitudinally striate and sparsely punctulate. Dorsum of head densely and finely reticulate-rugose, interspersed with punctures or foveae near posterior cephalic margin. Promesonotum and dorsum of petiolar node densely and finely microreticulate and coarsely punctate or reticulate-rugose; punctures elongate on promesonotum and round on petiolar node; propodeal declivity transversely rugulose. Third and anterior half of fourth abdominal tergites smooth and shiny between fairly sparse punctures, rest of segments smooth and shining. Body covered with yellowish, erect, slender hairs and pubescence. Integument black, appendages dark brown with lighter tarsae, antennal funiculi, and tip of gaster.

Type Material
Rakotonirina and Fisher (2014) - Lectotype worker, present designation, Madagascar, Bia di Antongil, 1897–1898 (A. Mocquerys), AntWeb specimen code: CASENT0102017. Paralectotype worker with same data as lectotype but with the following specimen code: CASENT0102018 (MSNG) [examined].

References based on Global Ant Biodiversity Informatics

 * Emery C. 1911. Hymenoptera. Fam. Formicidae. Subfam. Ponerinae. Genera Insectorum 118: 1-125.
 * 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.
 * Forel A. 1907. Ameisen von Madagaskar, den Comoren und Ostafrika. Wissenschaftliche Ergebnisse. Reise in Ostafrika 2: 75-92.
 * 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