Oxyepoecus striatus

Oxyepoecus striatus
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Insecta
Order:	Hymenoptera
Family:	Formicidae
Subfamily:	Myrmicinae
Tribe:	Solenopsidini
Genus:	Oxyepoecus
Species:	O. striatus
Binomial name
Oxyepoecus striatus Mackay, W.P. & Delsinne, 2011

The type specimens were collected from three pitfall samples.

Identification

Delsinne et al. (2012) - Its worker morphology places this species within the vezenyii species-group [3]. The worker is a small specimen with longitudinal striae covering the promesonotum and transverse striae on the dorsopropodeum. The clypeal teeth are well defined and sharp. The gyne and male are unknown.

This species is a member of the vezenyii species-group defined principally in having a predominantly smooth and glossy dorsum of the head. It is very similar to the relatively common Oxyepoecus vezenyii, but can be easily distinguished as the promesonotum of O. vezenyii is nearly completely smooth and glossy (the dorsopropodeum of O. vezenyii has transverse striae as in O. striatus).

Oxyepoecus striatus appears most similar to Oxyepoecus browni, which has a similar sculptured promesonotum, short posterior propodeal face, moderately well-developed costulae between the frontal carinae, and a large lobe-like subpetiolar process. Oxyepoecus striatus can be separated as being smaller; the clypeal teeth are well defined, sharp, and directed anteriorly (not lobe-like and directed inward). The frontal lobes are more widely spaced than those of O. browni (separated by 0.11mm) and the head is covered by coarse punctures (except for the smooth medial area).

Keys including this Species

• Key to Oxyepoecus of Paraguay
• Key to Oxyepoecus species

Distribution

Only known from the type locality.

Latitudinal Distribution Pattern

Latitudinal Range: -23.36666667° to -36.366667°.

North Temperate	North Subtropical	Tropical	South Subtropical	South Temperate

• Source: AntMaps

Distribution based on Regional Taxon Lists

Neotropical Region: Argentina, Paraguay (type locality).

Distribution based on AntMaps

Distribution based on AntWeb specimens

Check data from AntWeb

Countries Occupied

Number of countries occupied by this species based on AntWiki Regional Taxon Lists. In general, fewer countries occupied indicates a narrower range, while more countries indicates a more widespread species.

Estimated Abundance

Relative abundance based on number of AntMaps records per species (this species within the purple bar). Fewer records (to the left) indicates a less abundant/encountered species while more records (to the right) indicates more abundant/encountered species.

Biology

Explore Overview of Oxyepoecus biology  The following account is modified from Kempf (1974) and Albuquerque & 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

Known only from the worker caste.

Nomenclature

The following information is derived from Barry Bolton's Online Catalogue of the Ants of the World.

• striatus. Oxyepoecus striatus Mackay, W.P. & Delsinne, in Delsinne, et al. 2011: page, fig. 4 (w.) PARAGUAY.

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

Description

Worker

Measurements of holotype; paratypes (n = 2) between parentheses: TL 1.58 (1.6-1.7), HL 0.46 (0.46–0.48), HW 0.35 (0.35-0.36), EL 0.05 (0.07-0.07), SL 0.29 (0.29–0.31), PL 0.06 (0.06-0.06), PW 0.16 (0.17-0.18), PPL 0.08 (0.09-0.09), PPW 0.19 (0.21-0.22),WL 0.51 (0.49–0.51); CI 76 (75-76), SI 63 (62–65).

Mandible with four teeth, with diastema (gap) between basal and subbasal teeth; lateral clypeal teeth well-developed but small, not lobe-like, directed anteriorly; eye small, with about 18 ommatidia, five ommatidia in greatest diameter; scape in repose failing to reach posterior border of head by about two maximum widths; sides of head nearly straight, parallel, frontovertexal margin slightly convex; pronotal shoulder slightly marked with stria; inferior pronotal process well developed; notopropodeal groove poorly developed; propodeal angles developed, acute; subpetiolar process well developed, lobe-like, directed ventrally, anterior and posterior faces of petiole nearly parallel; two subpostpetiolar angles present, anterior and posterior faces of postpetiole nearly parallel; as seen from above, postpetiole much broader than petiole, postpetiole slightly angulate laterally.

Erect hairs abundant on mandibles, clypeus, dorsal surface of head, dorsum of mesosoma, petiole, postpetiole, all surfaces of gaster, legs with semierect hairs; appressed pubescence sparse, few hairs noticeable on head and gaster.

Mandibles smooth and shiny, with few scattered punctures, most of dorsum of head with scattered coarse punctures, medial area smooth and glossy, mesonotum with longitudinal parallel striae, dorsopropodeum with fine transverse striae, lateropronotum mostly smooth and glossy, mesopleuron and lateropropodeum striolate, nodes of petiole and postpetiole smooth and glossy, posterior face of postpetiole transversely striolate, gaster smooth and glossy.

Body color. Concolorous Medium Reddish Brown.

Type Material

Holotype worker. Paraguay: Presidente Hayes: Rio Verde, Lat: S 23.22, Long: W 59.20, 15-16.X.2003, Delsinne T., 24-hour pitfall sample, specimen number 32606, Museum of Comparative Zoology. Paratypes. Same data as holotype, three workers, in three 24- hour pitfall samples, specimen numbers 29523, 29531, 29667, RBINS, INBP. Images of the specimen number 29531 are available at http://projects.biodiversity.be/ants.

Etymology

From Latin, stria, referring to the striae covering the dorsum of the mesosoma.

References

• Delsinne, T., Mackay, W., Wild, A., Roisin, Y., Leponce, M. 2011. Distribution and diversity of the cryptic ant genus Oxyepoecus (Hymenoptera: Formicidae: Myrmicinae) in Paraguay with descriptions of two new species. Psyche, 2012 (doi:10.1155/2012/594302).