Leptogenys falcigera

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Leptogenys falcigera
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Ponerinae
Tribe: Ponerini
Genus: Leptogenys
Species group: maxillosa
Species: L. falcigera
Binomial name
Leptogenys falcigera
Roger, 1861

Leptogenys falcigera casent0003814 profile 1.jpg

Leptogenys falcigera casent0003814 dorsal 1.jpg

Specimen Label

Synonyms

Leptogenys falcigera is widespread but not common in the Malagasy region. This species generally occupies coastal areas and disturbed habitats in each island of the region and is thought to be introduced. In Madagascar, it is the dominant ponerine ant in the spiny forest/thicket habitat of the southern tip of the island. The dominance of this species in the south suggests that the species may be native or arrived on this island long ago, or recently introduced and rapidely spread in this type of habitat. The species was able to survive and dominate this southern region because environmental factors here resemble its place of origin. Workers of L. falcigera forage on the forest floor, in leaf litter, and on lower vegetation, and nest in live tree stems, in dead twigs or branches above the ground, and in rotten logs. (Rakotonirina and Fisher 2014)

Identification

A member of the maxillosa species group. Rakotonirina and Fisher (2014) - Worker. Mandible not closing tightly against broadly convex anterior clypeal margin; dorsum of body without standing hairs, but covered with very dense pubescence; sculpture shagreenate; anterior margin of clypeus covered with narrowly angulate translucent lamella; three peg-like setae usually projecting anteriorly from median border of clypeus; in dorsal view petiolar node longer than broad or as long as broad.

This species is very similar to Leptogenys maxillosa but can be easily separated by its elongate and narrower petiolar node (L. falcigera: DNI: 93–109; L. maxillosa: DNI: 113–133). Leptogenys falcigera can be distinguished from Leptogenys pavesii by the narrow and medially obtuse translucent lamella fringing its median clypeal lobe and the presence of three peg-like setae projecting anteriorly from the anterior margin of the median lobe. In L. pavesii, this fringing lamella is wide and broadly rounded and two peg-like setae project anteriorly from the anterior margin of the median lobe of the clypeus

Keys including this Species

Distribution

Distribution based on Regional Taxon Lists

Afrotropical Region: Comoros.
Indo-Australian Region: Guam, Hawaii, Marshall Islands, Micronesia (Federated States of), Northern Mariana Islands, Palau, Philippines.
Malagasy Region: Madagascar, Mauritius, Mayotte.
Oriental Region: India, Sri Lanka (type locality).

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Biology

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.

Castes

Nomenclature

The following information is derived from Barry Bolton's New General Catalogue, a catalogue of the world's ants.

  • falcigera. Leptogenys falcigera Roger, 1861a: 42 (w.) SRI LANKA. Forel, 1891b: 111 (m.). Senior synonym of insularis: Wilson & Taylor, 1967: 30. See also: Bolton, 1975a: 252.
  • insularis. Leptogenys insularis Smith, F. 1879: 675 (w.) HAWAII. Forel, 1899a: 118 (m.). Subspecies of falcigera: Forel, 1899a: 118. Junior synonym of falcigera: Wilson & Taylor, 1967: 30.

Unless otherwise noted the text for the remainder of this section is reported from the publication that includes the original description.

Description

Worker

Rakotonirina and Fisher (2014) - (16 specimens). HW: 1.41–1.66, HL: 1.42–1.69, CI: 96–105, SL: 1.34–1.58, SI: 90–100, PW: 0.94–1.10, WL: 2.29–2.73, PNH: 0.76–0.90, PNL: 0.65–0.80, PNW: 0.66–0.80, DNI: 93–109, LNI: 109–122.

Head broader than long, increasing in width to front, sides slightly convex and diverging anteriorly along length. Eye large, maximum diameter greater than widest portion of scape; extending beyond lateral edge of head in full-face view. Anteromedian lobe of clypeus borderedby narrow and obtusely angulate translucent lamella; usually three and rarely two or four peg-like setae projecting anteriorly at anterior margin of median lobe at base of lamella. Mandible slightly curved near base and become roughly straight apically; preapical tooth or denticle of mandible either absent or present near apical tooth. In dorsal view, petiolar node most often longer than broad and infrequently as long as broad. Dorsum of head, mesosoma, petiolar node, and third and fourth abdominal segments without standing hairs; whitish yellow pubescence very abundant. Head and body with dense shagreenate sculptures, interspersed with larger punctures. Black species with lighter tip of gaster; appendages dark brown to reddish brown basally and brown to light brown toward apex.

Type Material

Rakotonirina and Fisher (2014) - Holotype worker, Sri Lanka (H. Nietner) [location of type not known]. F. Smith’s worker type specimen is located at The Natural History Museum and was examined during the course of this study; it bears a blue syntype label in concordance with Smith’s description that the type-series includes several workers: “Not rare,..., workers only taken”. Conversely, the BMNH Accessions register only indicates a single specimen was deposited: “1879 no. 40. 1 Leptogenys insularis Sm. Sandwich Is (Oahu), presented by Rev. T. Blackburn, Honolulu”. Though this may imply that additional syntypes may not exist, and that the single specimen at BMNH is a holotype, we nonetheless designate this specimen as the lectotype.

The following notes on F. Smith type specimens have been provided by Barry Bolton (details):

Leptogenys insularis

Holotype worker in The Natural History Museum. Labelled “52” upon the stage card, and “Oahu. 79/40.” Acc. Reg.: “1879 no. 40. 1 Leptogenys insularis Sm. Sandwich Is (Oahu). Presented by Rev. T. Blackburn, Honolulu.” A blue syntype label is on the specimen (as opposed to a red holotype label) as the type-series appeared originally to contain several workers. Smith says, “Not rare,......workers only taken.” On the other hand, the specimen may well be unique as the accessions register specifically states “1.”

References

  • 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 252, see also)
  • Forel, A. 1891c. Les Formicides. [part]. In: Grandidier, A. Histoire physique, naturelle, et politique de Madagascar. Volume XX. Histoire naturelle des Hyménoptères. Deuxième partie (28e fascicule). Paris: Hachette et Cie, v + 237 pp. (page 111, 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.
  • Roger, J. 1861a. Die Ponera-artigen Ameisen (Schluss). Berl. Entomol. Z. 5: 1-54 (page 42, worker described)
  • Wilson, E. O.; Taylor, R. W. 1967b. The ants of Polynesia (Hymenoptera: Formicidae). Pac. Insects Monogr. 14: 1-109 (page 30, Senior synonym of insularis)