Corresponding author: Rick Overson (
Academic editor: M. Borowiec
In this study we revise the taxonomy of the genus
Overson R, Fisher BL (2015) Taxonomic revision of the genus
The genus
The present contribution includes all specimens of
Collection abbreviations follow Bolton (1980) and Evenhuis (2009). The material upon which this study is based is located, or deposited at the following institutions:
Sculpture of the head and dorsum of the mesosoma is of high diagnostic value in identifying Malagasy
When identifying Malagasy
Head in full-face view.
1 | Nine antennal segments present, palest and smallest of the Malagasy |
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– | Twelve antennal segments present; not as small as above (HL > 0.4 mm and HW > 0.3 mm); varying in size and color |
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2 | Cephalic foveae widely and evenly spaced such that they are only extremely rarely adjacent to one another; all cephalic foveae appear as if scooped out of a flat, shining surface, and completely lack raised margins at their perimeter (Fig. |
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– | Cephalic foveae of variable spacing but never as sparse as above; at a minimum, head with several clusters of two or more foveae which are directly adjacent in full-face view (Fig. |
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3 | Metanotal suture absent in dorsal view, in its place a smooth surface with no clear boundary dividing mesonotum and propodeum; posterior margin of the propodeum convex and crescent-shaped in dorsal view (Fig. |
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– | Metanotal suture present; posterior margin of the propodeum relatively straight in dorsal view (Fig. |
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4 | Vast majority of cephalic foveae densely positioned so they are directly adjacent to one another; vein-like ridges present running between foveae producing the appearance of a netlike pattern across the entire head (Fig. |
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– | Cephalic foveae variable in their spacing, but always with some foveae directly adjacent and others isolated from one another; usually with the frequency of adjacent foveae increasing laterally to medially (Fig. |
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5 | Coronal suture present on head which appears as a uniformly thin, linear scar that swells above the surrounding integument under high magnification (Fig. |
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– | Coronal suture absent on head; median cephalic band wider and more irregular, never uniformly swelling above the surface of the surrounding integument as a suture, appearing instead as a shining area devoid of foveae (Fig. |
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6 | Cephalic foveae small and densely positioned so that the vast majority are directly adjacent to one another with swollen ridges between; median cephalic band devoid of foveae is wide, usually wider at its base and narrowing posteriorly (Fig. |
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– | Cephalic foveae large, deep, and densely placed, joining to form a network of tall, jagged ridges; median cephalic band lacking foveae is usually thin and narrow, but its boundaries are irregular and jagged (Fig. |
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7 | Distinctly tricolored body with dark brown, uniformly colored head, lighter brown body, and pale yellow legs (Fig. |
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– | Not distinctly tricolored as above; some individuals possess dark brown on head but always at least with lighter brown present at the posterolateral corners of the head which resembles the color of the mesosoma (Fig. |
Head in full-face view.
Posterior margin of the head straight to weakly concave in full-face view; spacing of cephalic foveae highly variable, ranging from individuals with dense, directly adjacent foveae covering the entire head (known only from far eastern and northern Madagascar, see morphotype descriptions below), to individuals with foveae more widely spaced so that shining areas are visible between; median cephalic band devoid of foveae ranging from wide to extremely narrow but never appearing as a linear suture that is uniformly swollen above the level of the surrounding integument; apical tooth intermediate in length; evenly-space pronotal foveae range from shallow to deep; shallow foveae present on mesonotum and propodeum.
This widespread species has been collected from leaf litter from 10–1860 meters of elevation. While found most commonly in rainforest and montane rainforest, it has also been collected in Uapaca woodland, littoral rainforest, and tropical dry forest (Fig.
Three generalized morphotypes can be distinguished within this taxon; these vary in density of cephalic foveae and other co-occurring traits (Fig.
Under the above scheme, the lectotype and paralectotype of
MADAGASCAR: Antananarivo, Ankalalahana,
Head much longer than wide with lowest cephalic index on average of all Malagasy
The name of this species is a patronym dedicated to Laura D. Steger for her continual support during the course of this work and her either completely genuine—or expertly feigned—enthusiasm for being endlessly bombarded by information about ants.
This species has been collected in leaf litter primarily in rainforest with some collections from littoral rainforest and one in tropical dry rainforest, at elevations between 10–600 meters. Its range is restricted to eastern Madagascar and is seemingly disjunct, with most individuals collected from the northeast and only two locales known from the southeast near the coast. No individuals have been collected between Sahafina Forest in the north and Mahabo forest in the south, a distance of 500 km (Fig.
This species of
MADAGASCAR: Antsiranana, Ambondrobe, 41.1 km 175° Vohemar,
Twelve antennal segments; posterior margin of the head weakly concave in full-face view; small cephalic foveae densely positioned so that no flat, shining integument is present between; median cephalic band which is devoid of foveae does not appear to swell above the surrounding integument, but rather appears as a smooth, shining surface which is widest anteriorly, narrowing posteriorly; apical tooth intermediate in length; pronotum with foveae which range from shallow to deep and are interspersed regularly with punctures; mesonotum and propodeum consisting of large, shallow foveae; metanotal groove strongly visible, and mesopropodeal suture visible to barely visible, but some depression always present; posterior propodeal edge viewed dorsally is straight or only very slightly concave; no protruding lamellae of the posterior propodeum.
This species is named after the Seychelles archipelago, to which it is endemic. The species epithet is a noun in apposition, and thus invariable.
This species is known only from Seychelles and is found between 15–660 meters of elevation on the islands of Mahé, Conception, Thérèse, Silhouette, Praslin, La Digue, Félicité Island, and the Little Sister island group. It does not appear to have strict habitat preferences as it has been collected in mixed forest, littoral forest, non-native forest, palm forest, and coastal scrub.
SEYCHELLES: Conception Island,
Posterior head margin slightly concave with a noticeable notch medially; cephalic foveae dense and minute; virtually no area of the head lacking foveae in full-face view except at the extreme posterolateral corners; median cephalic band devoid of foveae is thin, linear, and slightly but uniformly swells above the surrounding integument; apical tooth intermediate in length; foveae on the pronotum are shallow, as well as more widely spaced and obviously larger than those on the head, with punctures present between; mesonotum and propodeum consisting of shallow foveae and punctures; metanotal groove visible dorsally, and mesopropodeal suture strongly visible in lateral view.
The name of this species comes from the Latin adjective meaning “fine”, “thin”, or “slender” and refers to the very delicate, net-like patterns produced by the sculpture on the head.
This common and widespread species is found in rainforest, montane rainforest, lowland rainforest, tropical forest, littoral forest, degraded forest, and marsh edge from 5–1325 meters of elevation (Fig.
MADAGASCAR: Andasibe, Mantadia NP, 7.i.2006 (
In full-face view, cephalic foveae become denser medially, so that laterally, foveae are separated by more than the diameter of one fovea, and medially, many foveae are directly adjacent and tend to form longitudinal chains of connected foveae; areas between foveae dark brown and shining; median cephalic area devoid of foveae not swelling above the surface of the surrounding integument and characterized as being widest anteriorly, narrowing posteriorly; apical tooth relatively short in length; eyes largest of all Malagasy
The rich brown color of the shiny integument of this taxon inspired the name “Talos”, after the living bronze statue that protected Europa from invaders in Greek mythology. The species epithet is an arbitrary combination of letters, and thus invariant.
This rare ant is known from a single locality in the Anjanaharibe-Sud Reserve in the province of Antsiranana (Fig.
Highest cephalic index on average of Malagasy
The name of this species is inspired by the vampire-like nature of its exceptionally long apical tooth. The species epithet is a Latinized adjective of the German and Hungarian word “vampir”.
This species is almost entirely restricted to northern Madagascar where it is found in litter in rainforest, littoral rainforest, and montane rainforest from 25–1200 meters of elevation. Intriguingly,
This species, which has similar cephalic scupturing to
MADAGASCAR: Antsiranana, Ampasindava, Andranomatavy Forest,
Cephalic foveae shallow, large, and most widely spaced of the Malagasy
The name of this new species is a combination of the Greek adjective “xero” meaning dry and the Latin noun “silva” for forest, as this species is known only from tropical dry forests in western Madagascar.
With its uniformly and widely spaced cephalic foveae,
Geographic distributions for Malagasy
Geographic distributions for morphotypes of
MADAGASCAR: Mahajanga, Parc National Tsingy de Bemaraha, 10.6 km ESE 123° Antsalova,
The fieldwork on which this study is based could not have been completed without the gracious support of the Malagasy Arthropod Inventory Team (Balsama Rajemison, Jean-Claude Rakotonirina, Jean-Jacques Rafanomezantsoa, Chrislain Ranaivo, Hanitriniana Rasoazanamavo, Nicole Rasoamanana, Clavier Randrianandrasana, Dimby Raharinjanahary, Njaka Ravelomanana, and Manoa Ramamonjisoa). We thank the following institutions for delivering authorizations for the capture, collection and exportation of ants—MADAGASCAR: Ministère de l’ Environnement et des Forêts and the Madagascar National Parks; SEYCHELLES: Seychelles Bureau of Standards, Ministry of Environment, and National Park Authority. In the Seychelles, we benefited from the generous help of Pat Matyot, Gérard Rocamora, and Gaëtan Galman of Island Conservation Society, Seychelles; Justin Gerlach from the Nature Protection Trust of Seychelles, Silhouette; Lindsay Chong-Seng and Nancy Bunbury of the Seychelles Islands Foundation (SIF) in Vallée de Mai and Aldabra; and many locals who offered their expertise, guidance, and companionship on each of the islands. Francisco Hita Garcia and Georg Fischer provided invaluable assistance contributing to this work. Michele Esposito provided expertise and time contributing to both the production of images for this revision, as well as the online databasing of specimens. Masashi Yoshimura and Flavia Esteves provided additional support and assistance aiding in the publication of this revision. Flavia Esteves also organized the R scripts for creating the maps and processed the shape files. This project was supported by National Geographic grant No. 8429-08 and National Science Foundation grants DEB-0072713, DEB-0344731, and DEB-0842395 to BLF.