Oxyepoecus mandibularis

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Oxyepoecus mandibularis
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Myrmicinae
Tribe: Solenopsidini
Genus: Oxyepoecus
Species: O. mandibularis
Binomial name
Oxyepoecus mandibularis
(Emery, 1913)

Oxyepoecus mandibularis casent0904585 p 1 high.jpg

Oxyepoecus mandibularis casent0904585 d 1 high.jpg

Specimen Labels

Only known from a single holotype specimen.

Identification

Kempf (1974) - According to the original description and figure, mandibularis is quite distinctive by larger size (single-spread measurement giving a total length of 3.0 mm!); larger, triangular mandibles which have the broad basal tooth neatly separated from the subbasal tooth by a deep cleft (as in Oxyepoecus punctifrons); long antennal scapes, the tip of which nearly attains the occipital border when in repose. In addition the entire dorsal surface of the head is sculptured and opaque, except for the smooth clypeal apron, finely reticulate-striate on frons, and finely striate with smooth intervals on cheeks; the promesonotal dorsum is somewhat irregularly but predominantly longitudinally striato-rugose, the basal face of the propodeum is regularly transversaly striate; the metanotal groove is scarcely impressed, the propodeal armature consists of scarcely protruding, blunt, paired tubercles; the petiolar node is not noticeably incrassate in profile nor conspicuously dilated laterad in dorsal view; the postpetiole is only one and a half times as broad as long.

The particular mandibular dentition and the long antennal scapes remind one of Oxyepoecus punctifrons which, however, is very light in color and scarcely sculptured at all. The closest species seems indeed to be Oxyepoecus rastratus, from which mandibularis differs in larger size, different mandibular dentition, longer scapes, more irregular sculpture on promesonotum, inconspicuous and blunt propodeal armature, and less antero-posteriorly compressed and laterally scarcely expanded petiolar and postpetiolar nodes. In the appended key, mandibularis would probably run to rastratus from which it is easily separated by the already mentioned characters.

Distribution

Distribution based on Regional Taxon Lists

Neotropical Region: Bolivia (type locality).

Distribution based on AntMaps

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Distribution based on AntWeb specimens

Check data from AntWeb

Biology

Nothing is known about the biology of this species.

The following account of the biology of species within the genus is based on, and modified from, Kempf (1974) and Albuquerque and Brandão (2009).

Our knowledge of Oxyepoecus ants still rests exclusively on chance discoveries. Since about 95% of the known specimens were taken as strays in berlesates of forest floor cover, very little may be said about the biology of Oxyepoecus species except for being denizens or at least foragers in this particular habitat. The minute size of Oxyepoecus, their color and cryptic habits hamper direct observation of their habits in natural conditions (especially inside shaded forest where light rarely reaches the ground).

Oxyepoecus has been considered very rare in collections, but our studies show that they are rather common in the leaf litter of most localities where recent surveys have been conducted in the Mata Atlântica (see Comments in Albuquerque & Brandão, 2004). It is interesting to note that one of these localities we recently surveyed, Cunha, São Paulo state has four Oxyepoecus species (Oxyepoecus myops, Oxyepoecus rastratus, Oxyepoecus longicephalus and Oxyepoecus rosai), three of which were found in one square meter of leaf-litter (sample 48; all but O. rosai). In Salesópolis, SP, we recorded five of the 17 known Oxyepoecus species (O. myops, Oxyepoecus punctifrons, O. rastratus, O. rosai and Oxyepoecus vezenyii). Both Cunha and Salesópolis are localities circa 1000 m above sea level, covered by pristine evergreen dense forest.

Although Oxyepoecus samples come mostly from forested localities, workers have been less frequently collected in places with more open vegetation, as open “cerrados” (savannas). Comparing the examined material of most species, one can see that the specimens mostly come from the same localities. This is because these localities we surveyed recently, extracting ants from the leaf-litter, or localities where careful collectors lived most of their lifes (Seara, SC, for instance, where F. Plaumann worked many years).

Kusnezov (1952) put forward the hypothesis that Oxyepoecus ants are inquilines of Pheidole and Solenopsis nests. Evidence exists for their being symbiotic relationships between several Oxyepoecus species and other Myrmicinae ants (details provided here). Independent colonies seem to be vouched for by Oxyepoecus punctifrons and Oxyepoecus rastratus. The types of the former, collected at Rio Negro, Paraná State, Brazil, came from a nest that had over 60 workers living by themselves, but no further information is available. A few workers of the same species, at Campos do Jordão, São Paulo State, Brazil, were also found on a dead twig, between the bark and an overgrown cover consisting of lichens and mosses. The types of the var. luederwaldti (= rastratus) are from a very small colony nesting under the bark in a simple cavity within the alburnum of a tree (Luederwaldt, 1926: 275). Lenko's rastratus specimens from Caraça, Minas Gerais State, had their nest within a decaying log on the ground in a forest. A similar nesting situation was found from a more recent collection from Paraguay (col A. Wild).

The fact that Oxyepoecus workers are relatively abundant in material extracted from leaf litter samples, while dealate gynes are seldom found in the litter and larvae have never been found in litter samples, suggests that they nest in the soil, where the gynes and larvae live, but workers leave the nest periodically to search for food. Oxyepoecus has been attracted to honey or sardine baits set over the ground in different habitats, which suggests they are generalist foragers. In just one case, a gyne and two workers of O. punctifrons (Vezenyii group) were found by Rogerio R. da Silva under the bark of a the canopy branch in a recently fallen Leguminoseae (Albuquerque & Brandão, 2004).

Castes

Only known from a single holotype worker.

Nomenclature

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

  • mandibularis. Monomorium (Martia) mandibulare Emery, 1913b: 261, fig. 12 (w.) BOLIVIA. Combination in Martia: Kusnezov, 1952h: 722; in Oxyepoecus: Ettershank, 1966: 146. See also: Kempf, 1974b: 491; Albuquerque & Brandão, 2009: 294.

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

Description

Worker

Ouvrière. - Brun ferrugineux, membres plus clairs, tête, excepté les mandibules, et segment basal du gastre brun noirâtre. Tête mate, très finement réticulée, sur le front, le réticule se résout en fines stries et, sur les joues, le fond se montre luisant; épistome et mandibules luisants; corselet strié, le promésonotum en long, mais assez irregulièrement, l'epinotum transversalement et regulièrement. Poils longs et fins, pubescence presque nulle.

La tête est de peu plus longue que large, si on ne compte pas la saillie que forme l'épistome avec ses dents; mais si on en tient compte, la tête est alors presque une fois et demie aussi longue que large. Les mandibules sont longues et armées de 4 grandes dents dont la basal est épaissé et séparée des autres. L'épistome est bicaréné et armé, comme dans M. vezenyii et rastratum. Le scape atteint presque le bord occipital; massue de 3 articles, le dernier plus long que les deux autres, ceux-ci presque égaux. Pas de suture promésonotale, le profil du corselet n'est presque pas impressioné dans la suture méso-épinotale; l'épinotum a la face descendante beaucoup plus courte que la face basale; cette dernière est droite, presque verticale, bordée d'une arrête sur les côtés, qui se termine en haut par une petite saillie mousse. Vu par-dessus, le petiole paraît claviforme; de profil, it est pédonculé et surmonté d'un noeud près de deux fois aussi haut que long; par-dessus, le noeud est un peu plus large que long; postpétiole ovale, à peine de moitié plus large que le noeud du pétiole. - L. 3 mill.

Bolivie: Songo; Staudinger et Bang-Haas, un exemplaire.

Cette curieuse espèce se rapproche de vezenyii et surtout de rastratum. Ce dernier (dont je possède un type) a les mandibules à 4 grosses dents, comme dans la nouvelle espèce; mais la dent basal n'est pas détachée comme chez mandibulare. L'épistome de rastratum a les dents médiales plus longues et les latérales moins prononcées que chez mandibulare».

Type Material

Kempf (1974) - The single holotype, a worker specimen, probably kept in the Emery collection at Genova. It was not seen during this investigation.

References

  • Albuquerque, N. L. d. and C. R. F. Brandão. 2009. A revision of the Neotropical Solenopsidini ant genus Oxyepoecus Santschi, 1926 (Hymenoptera: Formicidae: Myrmicinae): 2. Final. Key for species and revision of the Rastratus species-group. Papéis Avulsos de Zoologia (São Paulo). 49:289-309.
  • Emery, C. 1913c. Études sur les Myrmicinae. [V-VII.]. Ann. Soc. Entomol. Belg. 57: 250-262 (page 261, fig. 12 worker described)
  • Ettershank, G. 1966. A generic revision of the world Myrmicinae related to Solenopsis and Pheidologeton (Hymenoptera: Formicidae). Aust. J. Zool. 14: 73-171 (page 146, Combination in Oxyepoecus)
  • Kempf, W. W. 1974b. A review of the Neotropical ant genus Oxyepoecus Santschi (Hymenoptera: Formicidae). Stud. Entomol. 17: 471-512 (page 491, see also)
  • Kusnezov, N. 1952k [1951]. Acerca de las hormigas simbióticas del género Martia Forel (Hymenoptera, Formicidae). Acta Zool. Lilloana 10: 717-722 (page 722, Combination in Martia)