Oxyepoecus vivax

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Oxyepoecus vivax
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Myrmicinae
Tribe: Solenopsidini
Genus: Oxyepoecus
Species: O. vivax
Binomial name
Oxyepoecus vivax
Kempf, 1974

This species is only known from a holotype queen specimen.

Identification

The diagnostic characters of O. vivax gynes in relation to the other species in the Vezenyii group are the elongate mandibles, the blunt clypeal denticles and the relatively scarcely laterad expanded postpetiole (Albuquerque and Brandão 2004).

Distribution

The lone holotype specimen was found in Minas Gerais State, Brasil.

Distribution based on Regional Taxon Lists

Neotropical Region: Brazil (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 the queen.

Nomenclature

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

  • vivax. Oxyepoecus vivax Kempf, 1974b: 508, figs. 31-33, 38, 39 (q.) BRAZIL. Albuquerque & Brandão, 2004: 77 (q.).

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

Kempf 1974 Oxyepoecus fig 31-37.jpg

The unusually elongate and linear mandibles place vivax in the vicinity of Oxyepoecus inquilinus (the female of which is still unknown), differing, however, in the blunt clypeal armature, the entirely sculptured frons, the globose, not scalelike petiolar node, the relatively little expanded postpetiole.

The relatively large size is shared with Oxyepoecus mandibularis (the latter likewise known only in the worker caste, and not seen during this study), which has short, triangular mandibles with a deep cleft between basal and subbasal tooth on the chewing border, and the cephalic dorsum more heavily and extensively sculptured.

From the already known queens in genus Oxyepoecus, vivax is readily separated by its much larger size, the long, linear mandibles, the irregular sculpture on basal face of propodeum.

Description

Queen

(holotype). Total length 3.8 mm; head length 0.75 mm; head width 0.67 mm; scape length 0.58 mm; maximum diameter of eyes 0.29 mm; Weber's length of thorax 1.09 mm; maximum width of pronotum 0.61 mm; hind femur length 0.73 mm; fore wing length 2.4 mm; hind wing length 2.0 mm; petiole width 0.27 mm; postpetiole width 0.32 mm; cephalic index 89. Color reddish brown; vertex, occiput, posterior portion of sides of head, and gaster somewhat infuscated; mandibles, legs except coxae, and antennae yellowish brown. Wings slightly

Kempf 1974 Oxyepoecus fig 38-42.jpg

infumated, veins light brown. Integument smooth and shining with the following exceptions: cheeks and lateral portions of clypeus finely longitudinally costulate; frontal carinae and frons finely longitudinally costulate, the posterior portions rather indistinct, not reaching laterally the eyes nor posteriorly the ocelli; occiput with transverse costulae; dorsum of pronotum feebly and obliquely costulate; paraptera and scutellum regularly longitudinally costulate; basal face of propodeum with oblique, asymetrically disposed rugulae or costae; mesopleura, metapleura and sides of propodeum with patches of costulate sculpture; sides and posterior surface of petiolar and postpetiolar node horizontally, respectively transversely costulate. Hairs abundant, standing on dorsum of head and thorax, oblique on petiole and gaster; shorter, inclined hairs on dorsum of head, sides of head, mandibles, antennae and legs.

Head. Mandibles elongate, sublinear, the basal border longer than the chewing border with which it scarcely forms an angle; a broad but shallow diastema between the small basal and subbasal tooth. Median apron of clypeus protruding, with the usual longitudinal, anteriorly diverging carinae, but the anterior teeth are blunt and scarcely prominent, and the lateral dentides minute and inconspicuous. Frontal carinae, except the anterior curvature, absolutely straight and parallel, the distance between their outer edges slightly less than one third of the head width, as measured behind the eyes. Frontal area smooth, impressed, ill-delimited. Eyes huge, prominent, with several hundred ommatidia, oval in outline. Ocelli small. Antennal scapes nearly reaching the narrowly rounded occipital corner when laid back over the head as much as possible. Funicular segments I, VIII, IX and X much longer than broad, II-VI somewhat broader than long, VII about as long as broad. Occiput in full-face view slightly excavated.

Thorax. Pronotum entirely declivous in the middle, the sides submarginate, the shoulders practically rounded, scarcely marked. Propodeal armature consisting of short yet pointed spines; in dorsal view their length is less than half the distance between the inner side of their bases. Declivous face of propodeum slightly excavate and laterally carinate. Wings: note the variation in the same individual, where the discoidal cell is reduced to a small solid rectangle in the left fore wing, while it is normal in the right fore wing. Hind wing with 6 hamuli.

Petiole and postpetiole. Petiole pedunculate, subpetiolar tooth small, node globose, in dorsal view only slightly shorter than broad, not expanded laterad nor antero-posteriorly compressed: postpetiole likewise little compressed antero-posteriorly and very little expanded laterad, not conspicuously broader than petiolar node; anterior subpostpetiolar process very prominent, but not bidentate. Gaster not excised nor truncate in front.

Type Material

Kempf (1974) - A single female (holotype, WWK n. 8836) , collected by Dr. C. A. C. Seabra & Lt.-Cel. Moacyr Alvarenga at Pedra Azul, altitude 800 m, XI-1972, in the northeast of the State of Minas Gerais, Brazil.

References

  • Albuquerque, N. L. d. and C. R. F. Brandão. 2004. A revision of the Neotropical Solenopsidini ant genus Oxyepoecus Santschi, 1926 (Hymenoptera: Formicidae: Myrmicinae). 1. The Vezenyii species-group. Papéis Avulsos de Zoologia (São Paulo). 44:55-80. DOI: 10.1590/S0031-10492004000400001 (page 77, queen described)
  • 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.
  • Kempf, W. W. 1974b. A review of the Neotropical ant genus Oxyepoecus Santschi (Hymenoptera: Formicidae). Stud. Entomol. 17: 471-512 (page 508, figs. 31-33, 38, 39 queen described)