Worker specimens of L. arcirostris look for prey on the surface of the forest floor and in leaf litter, and their colonies are mostly found in rotten logs and under rocks.
A member of the arcirostris complex of the truncatirostris species group. Rakotonirina and Fisher (2014) - Worker. Clypeus with median carina, width when measured from anterior level of torulus to anteromedian margin of clypeus less than or equal to maximum diameter of scape; in full-face view head longer than broad, antennal scape relatively short; few short suberect hairs and abundant pubescence present on dorsum of head, mesosoma and gaster.
Leptogenys arcirostris is closely related to Leptogenys borivava and Leptogenys alatapia but in L. borivava, the body size is smaller (HW: 0.97–1.01, WL: 1.77–1.87), and the dorsum of the head, mesosoma, petiole, and gaster is with reduced pubescence and covered with long standing erect and suberect hairs. The head is much broader (CI: 105–109) in L. alatapia.
Keys including this Species
Recent surveys of ants across Madagascar have found this species only in the southern part of the island. It ranges from the montane rainforests of Atsirakambiaty near Itremo and Anja Reserve to the gallery forests of the PN Isalo and Mitea Forest, through the spiny forests/thickets of the PN Tsimanampetsotsa and the dry forest habitats of Vohidava near Amboasary. However, the type locality of L. arcirostris is Moramanga, in central-eastern Madagascar. Leptogenys arcirostris can survive in a wide range of habitats and may have had a larger geographic range, extending to Moramanga, in the recent past. Anthropogenic disturbance and deforestation may have caused local extinction in the northern part of its range.
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.
- arcirostris. Leptogenys (Machaerogenys) arcirostris Santschi, 1926a: 25 (w.) MADAGASCAR. 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) - (10 specimens). HW: 1.18–1.38, HL: 1.27–1.43, CI: 93–97, SL: 1.32–1.46, SI: 103–112, PW: 0.72–0.95, WL: 2.08–2.32, PNH: 0.68–0.74, PNL: 0.53–0.62, PNW: 0.60–0.68, DNI: 107–115, LNI: 119–133.
Head broader in front than behind, the sides more or less straight, diverging anteriorly and rounding in a convex line with a straight posterior margin. Eye large, not breaking the lateral cephalic border. Antennal scape relatively short (SI: 103–112). In full-face view, clypeus with broad and evenly rounded anterior margin, fringed by wide, white-yellowish membrane; median lobe short, width when measured from anterior level of torulus to anteromedian margin of clypeus less than or equal to maximum diameter of scape; medial longitudinal carina present. With head in full-face view and mandible fully closed, blades superimposed on one another, with internal surface of first blade tightly closed against clypeus along their length and that of the second blade against external face of the first. In dorsal view, metanotal groove transversely striate; in lateral view, propodeal lobe bluntly angular. With petiole in profile, anterior face of node vertically straight, posterior face convex, both forming rounded angles with dorsal margin. Mandible longitudinally striate, interspersed with piligerous punctures. Dorsum of head, pronotum and petiolar node densely and finely reticulate-punctate, punctures becoming smaller near posterior margin of head. Rest of dorsum of mesosoma finely reticulate-rugose. Mesopleuron and lower part of propodeum reticulate-rugulose, with scattered large punctures. Propodeal declivity transversely rugulose. Third abdominal tergite densely and finely reticulate-rugose to finely reticulate-punctate. Standing short hairs few; pubescence quite abundant on dorsum of head and rest of body. Color black to dark brown; base of appendages brown, their apices and tip of gaster lighter in color.
Rakotonirina and Fisher (2014) - Holotype worker, Madagascar, Moramanga (Descarpentries) AntWeb specimen code: CASENT0101132 (Naturhistorisches Museum, Basel) [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)
- Rakotonirina, J.C. & Fisher, B.L. 2014. Revision of the Malagasy ponerine ants of the genus Leptogenys Roger (Hymenoptera: Formicidae). Zootaxa 3836, 1-163.
- Santschi, F. 1926a. Trois notes myrmécologiques. Ann. Soc. Entomol. Fr. 95: 13-28 (page 25, worker described)