Leptogenys imerinensis

Recently-recorded worker specimens were found foraging on lower vegetation and one colony was found in a rotten log. JCR was able to observe the hunting behavior of the workers during field work in the forest corridor of Analamay-Mantadia. They ran closely one after another, in a single line and along the forest floor and on lower vegetation, to locate the prey site, about 10 meters from the nest. Then they returned to the nest individually with the prey, which consisted of isopods. Subsequently, workers emerged from the nest one after the other and ran singly before arriving at the site of the prey. Each worker returned to the nest individually or in pairs with one isopod clutched between the clypeus and their curved, elongate, and narrow mandibles. Some workers were not carrying any prey when they returned to the nest. (Rakotonirina and Fisher 2014)

Identification
A member of the imerinensis complex of the incisa species group. Rakotonirina and Fisher (2014) - Worker. Anterior margin of medial clypeal lobe with one pair of small, peg-like setae projecting anteriorly; medial clypeal carina bluntly rounded along its length; antennal scape relatively short (SI: 115–118), less than its apical third extending beyond posterior margin of head; in dorsal view, mesosoma consists of three visible segments, without discernible segment between metanotal groove and propodeum; larger species.

Leptogenys imerinensis can be separated from Leptogenys namana by its blunt median clypeal carina and larger size, while the latter has a sharp median clypeal carina and smaller body size. It can be confounded with Leptogenys manja, but the latter possesses longer antennal scape (SI: 136–140). The species may be confounded with Leptogenys suarensis and Leptogenys gracilis but the latter two species have four mesosomal divisions (an additional suture is present between the metanotal groove and the propodeum) in dorsal view and a smaller body size, while L. imerinensis has only three mesosomal segments and is larger.

Key to Malagasy Leptogenys

Distribution
Leptogenys imerinensis only occurs on the central-eastern plateau of Madagascar. Its first description was based on worker and male specimens found in Andrangoloaka and Perinet. Recent ant surveys in 2012 have found this species in the Ankerana Forest and the PN Mantadia-Andasibe. (Rakotonirina and Fisher 2014)

Distribution based on Regional Taxon Lists
Malagasy Region: Madagascar.

Nomenclature

 *  imerinensis. Leptogenys incisa var. imerinensis Forel, 1892l: 242 (w.m.) MADAGASCAR. Junior synonym of incisa: Bolton, 1975a: 298. Revived from synonymy: Rakotonirina & Fisher, 2014: 84. Raised to species: Rakotonirina & Fisher, 2014: 84.

Rakotonirina and Fisher (2014) - This species has been considered a subspecies of L. incisa since its first description. Bolton (1975), in his review of the species from the Malagasy region, was not able to discern the species boundaries of some forms because his study was based on only a few type specimens and insufficient collections. Based on the analysis of the new collections sampled from ant surveys in 2012, it is now clear that L. imerinensis merits species designation. Over the past 15 years of ant inventories in Madagascar, Leptogenys imerinensis was only found during the 2012 ant surveys in the Corridor Forestier Analamay-Mantadia and the Ankerana Forest. Lectotype and paralectotype specimens of L. imerinensis chosen during this study are those that were collected from the type locality “Forêt d’Andrangoloaka” mentioned by Forel in his original description of the subspecies.

Worker
Rakotonirina and Fisher (2014) - (5 specimens). HW: 1.51–1.55, HL: 1.72–1.78, CI: 87–89, SL: 1.74–1.81, SI: 115–118, PW: 1.15–1.20, WL: 2.92–3.10, PNH: 0.88–0.90, PNL: 0.88–0.94, PNW: 0.81–0.88, DNI: 90–95, LNI: 94–100.

Head subquadrate, with sides weakly convex and anteriorly diverging; posterior cephalic margin feebly concave. Eye large and slightly convex. With antennal scape laid straight back on head, in full-face view, its apex surpasses the posterior margin by roughly one-third its length. Clypeus broadly triangular, covered with narrow translucent lamella; median lobe with bluntly rounded longitudinal carina; pair of peg-like setae present on anteromedian margin. Mandible long and slender, with slightly stronger curve near base; inner margin concave, with small preapical tooth or denticle near sharp apical tooth; basal groove narrowly impressed. In cephalic full-face view, hypostomal teeth not visible. In profile, mesosoma short and high; posterior margin of propodeum without toothlike lobe. In dorsal view, metanotal groove impressed, transverse rugulae present; small and narrow sclerite present between metanotal groove and propodeum; in oblique profile, surface of propodeal declivity well delimited, junction between posterior and lateral faces of propodeum angulate. With petiole in dorsal view, node longer than broad; in profile, node relatively long, anterior face rounding to the dorsum, forming a distinct angle with a posterior face that slopes slightly forward. Constriction between third and fourth abdominal segments clearly visible. Mandible mostly smooth and shining, interspersed with piliferous punctures, apical halves with almost effaced, fine striation. Head dorsum finely rugulose in front of level of eyes, sculpture becoming densely and finely reticulate-rugulose towards posterior portion, with larger punctures near posterior cephalic border. In dorsal view, mesosoma generally densely and finely microreticulate, superimposed by shallow, elongate punctures on promesonotum, and dense and fine reticulate-rugulae on propodeal dorsum; declivitous surface with transverse rugae. Sculpture of dorsum of petiolar node as on promesonotum but with rounded punctures. Abdominal tergites III and IV densely microreticulate, superimposed with shallow elongate punctures, punctures much more superficial than those on promesonotum. Erect hairs slender; pubescence less on dorsum of mesosoma, petiolar node and the following abdominal tergites. Body color black, with brown apical portion of appendages and tip of gaster.

Type Material
Rakotonirina and Fisher (2014) - Lectotype worker, present designation, Madagascar, Foret d’Andrangoloaka [-19.0, 47.95, 1389 m] (Sikora), AntWeb CASENT0101795 (lower specimen of two workers on a pin). Paralectotype worker, same data as lectotype but with specimen code: CASENT0101825 [examined].