Oxyepoecus bidentatus

The fact that workers were extracted from leaf litter (Winkler method) or were collected in pitfall samples, while no gynes were found, suggests that this species nests in the soil, but workers forage in the leaf litter when abiotic conditions are favorable. Localities where the species was found have a mean annual rainfall and temperature ranging from 593 to 887mm and from 23 to 25◦C, respectively. (Delsinne et al. 2012)

Identification
Delsinne et al. (2012) - Its worker morphology places this species within the rastratus species-group. The reticulate-costulate dorsal surface of the head and the well-defined subpostpetiolar process, forming a pair of prominent blunt teeth, separate O. bidentatus from all the other species of Oxyepoecus.

Oxyepoecus bidentatus is the only species of the genus to have both the dorsal surface of the head entirely covered by sculpture and a bidentate subpostpetiolar process. The anterior subpostpetiolar process of Oxyepoecus bruchi of the vezenyii species-group is also prominent and bidentate, but the dorsal surface of the head is mainly smooth and shining except for two patches of fine, longitudinal rugulae which do not reach posteriorly to the vertex margin nor laterally to the compound eye. Criteria separating O. bidentatus from other species of the rastratus species group are the mesopleuron and lateropropodeum covered by longitudinal costae (and not reticulate as for Oxyepoecus myops, Oxyepoecus rosai, and Oxyepoecus reticulatus), and the presence of a reticulate-costulate sculpture on the dorsal surface of the head reaching posteriorly to the vertexal margin and laterally to the compound eye.

Key to Oxyepoecus of Paraguay

Distribution
Oxyepoecus bidentatus was found in three localities of the Paraguayan dry Chaco. Because the maximal distance between localities was 340 km, O. bidentatus is suspected to be widely distributed in xeromorphic Chacoan forests, even if rarely found.

Distribution based on Regional Taxon Lists
Neotropical Region: Argentina, Paraguay.

Castes
The gyne and male are unknown.

Nomenclature

 *  bidentatus. Oxyepoecus bidentatus Delsinne & Mackay, in Delsinne, et al. 2011: page, figs. 2, 3 (w.) PARAGUAY.

Worker
Measurements of holotype, paratypes (n = 2) between parentheses: TL 1.94 (1.86–1.90), HL 0.52 (0.51–0.55), HW 0.44 (0.42–0.46), EL 0.07 (0.06-0.07), SL 0.32 (0.32–0.35), PL 0.07 (0.07–0.11), PW 0.17 (0.19–0.23), PPL 0.09 (0.08–0.12), PPW 0.22 (0.25–0.28), WL 0.63 (0.60–0.64), CI 85 (83-84), and SI 62 (63-64).

Lateral clypeal teeth are well developed, directed anteriorly; eye small, about 16–18 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 gently angulate, marked with striae; notopropodeal (=metanotal) groove indistinct; propodeal angles developed, with two medium-sized acute teeth; subpetiolar process well-developed, lobe-like, directed ventrally; subpostpetiolar process well-developed, forming pair of blunt teeth, directed ventrally; nodes of petiole and postpetiole high and dorsally rounded, compressed anteroposteriorly; in lateral view, petiolar node higher than postpetiolar node; as seen from above, postpetiole much broader than petiole.

Long erect hairs abundant on clypeus, vertex, dorsum of mesosoma, petiole, postpetiole, all surfaces of gaster; mandibles, antennae, legs, and dorsal surface of head with abundant shorter semierect hairs.

Mandibles smooth and shiny, with few scattered punctures; head dorsum reticulate-costulate, lateral costulae attain compound eye and posteriorly vertexal margin; dorsopronotum and mesonotum longitudinally costate; dorsopropodeum transversely costate (about 10–12 costae on dorsal face), anterior half of the lateropronotum mostly smooth and glossy, sometimes with faint longitudinal costae; posterior half of the lateropronotum, mesopleuron and lateropropodeum covered by sparse longitudinal costae; nodes of petiole and postpetiole transversely costate; gaster smooth and glossy with sparse punctures.

Body Color. Concolorous 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 29272, SIDbase, RBINS). Images of the holotype are available at http://projects.biodiversity.be/ants.

Paratype workers. Paraguay: Presidente Hayes: Rio Verde, Lat: S 23.22, Long: W 59.20, 15-16.X.2003, Delsinne T., one worker, 24-hour pitfall trap, specimen number 32013, MCZC; Boqueron: T. Enciso N.P., Lat: S 21.21, Long: W 61.66, 03–05.XI.2001, Leponce M., five workers in three Winkler samples, RBINS, INBP, specimen numbers 7598, 7683, 7684, 7698, and 32605 (scanning electron microscope (SEM) pictures of the specimen number 7684 are available at http://projects.biodiversity.be/ants); Boqueron: Garrapatal, Lat: S 21.45, Long:W61.49, 05-06.XI.2001, Leponce M., one worker, Winkler sample, specimen number 24606, RBINS.

Etymology
From Latin, bidens, referring to the subpostpetiolar process forming a pair of well-defined teeth.