A common species, foraging behavior for this species is carried out mostly on the forest floor and rarely above ground on low vegetation. In the RP Berenty, workers of L. truncatirostris were found carrying larvae and cocoons and exhibiting tandem running during a nest relocation. This species generally nests in rotten logs, rotting bamboo, in soil layers, under rocks and under dead wood.
A member of the truncatirostris complex of the truncatirostris species group. Rakotonirina and Fisher (2014) - Worker. Clypeus wide and transverse, without projecting anteromedian lobe; median clypeal carina lacking; lateral portion meets the anterior margin of clypeus in a blunt angle. In profile, mandible curved dorsally with midpoint markedly dorsal of mandible insertion; distal half of blade slightly broader and flattened, the surface with effaced fine striation; in profile, third abdominal segment densely and finely punctate, dorsum of mesosoma, petiolar node, and gaster with numerous pubescences.
Leptogenys truncatirostris is very similar to Leptogenys diana but the latter can be distinguished by the broadly rounded anterior clypeal margin, the absence of pubescence on the dorsum of the body, and the presence of microreticulation with sparse punctures on the third abdominal tergite. Also, the basal third of the mandible is more robust and the distal half is broader and finely striate
Keys including this Species
As one of the most common species within the truncatirostris group, L. truncatirostris is widespread in western Madagascar, occurring from dry forest on Tsingy, gallery forest, littoral forests in the north to south-west as well as spiny bush and thicket habitats in the extreme south of the island. This species also can be discovered in anthropogenic habitats such as disturbed forests and roadsides. (Rakotonirina and Fisher 2014)
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.
- truncatirostris. Leptogenys truncatirostris Forel, 1897c: 195, fig. 2 (w.) MADAGASCAR. Forel, 1907g: 76 (m.). Combination in L. (Machaerogenys): Emery, 1911d: 101. 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) - (15 specimens). HW: 1.55–1.79, HL: 1.67–1.89, CI: 93–101, SL: 1.65–1.94, SI: 103–110, PW: 1.00–1.16, WL: 2.67–3.10, PNH: 0.88–1.03, PNL: 0.75–0.94, PNW: 0.72–0.89, DNI: 84–106, LNI: 106–119.
Head broadest anterior to eyes; sides slightly diverging anteriorly throughout its length; posterior margin weakly concave. Eye large, size between one-third and one-fourth the length of side of head; not breaking outline of lateral cephalic margin in full-face view. Mandible elongate; in profile, mandible strongly bent downward; in full-face view, blade widest near distal half, then progressively decreasing in breadth through apical tooth; preapical tooth may be present. Clypeus widely transverse anteriorly, junction of lateral section with anterior margin visibly angulate; anterior margin bordered by wide and thick yellowish membrane; median carina absent. Antennal scape fairly short, extending beyond posterior border of head by roughly one-fourth its length. With mesosoma in dorsal view, metanotal groove with transverse stration; in profile, propodeal lobe a blunt angle or absent. Dorsum of head reticulate-punctulate to reticulate rugulose. Apical half of mandible densely and finely striate and with reddish-orange surface. In dorsal view, mesosoma and petiolar node densely and finely reticulate-rugulose, interspersed with small punctures; propodeal declivity transversely striate. In profile, third abdominal tergite variably sculptured, either densely punctulate or microreticulate with scattered punctulae. Standing hairs and abundant pubescence present on mesosoma, petiolar node, and gaster. Body color black to dark brown; appendages brown at the base and becoming lighter toward the apex. Variation. Leptogenys truncatirostris shows considerable geographic variation. Two different forms have been recorded together in the RS Bemarivo. The form that most closely matches the holotype has the mandible with a slender median portion. The other form possesses mandibles that are much more robust and have a broadened median portion. Specimens collected from another site, RP Berenty, have a more rounded anterior clypeal margin.
Rakotonirina and Fisher (2014) - Lectotype worker, Madagascar, Nosy-be (Voeltzkow) present designation, AntWeb specimen code: CASENT0101940 (Musee d'Histoire Naturelle Genève) [examined]. Paralectotypes: series of 6 workers same data but specimen coded as: CASENT0101914, CASENT0101714, CASENT0101975, CASENT0101727, CASENT0101626 (MHNG) [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 101, Combination in L. (Machaerogenys))
- Forel, A. 1897d. Ameisen aus Nossi-Bé, Majunga, Juan de Nova (Madagaskar), den Aldabra-Inseln und Sansibar, gesammelt von Herrn Dr. A. Voeltzkow aus Berlin. Mit einem Anhang über die von Herrn Privatdocenten Dr. A. Brauer in Marburg auf den Seychellen und von Herrn. Abh. Senckenb. Naturforsch. Ges. 21: 185-208 (page 195, fig. 2 worker described)
- Forel, A. 1907i. Ameisen von Madagaskar, den Comoren und Ostafrika. Wiss. Ergeb. Reise Ostafr. 2: 75-92 (page 76, male 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.