Oxyepoecus plaumanni

Only known from Brazil.

Identification
The present species is closest to the sympatric Oxyepoecus rastratus. The worker exhibits the following diagnostic features: costulae on disc of cephalic dorsum not attaining laterally the upper orbit of eyes nor posteriorly the occipital border in full-face view; eyes smaller, with only 5-6 facets in a row across the greatest diameter and less than 20 ommatidia in all. Petiolar node not compressed nor expanded laterad. The same differences, except the eye character, hold for the females of both species, while plaumanni, in addition, has the mesonotal scutum. entirely smooth and shining.

Distribution based on Regional Taxon Lists
South and São Paulo State, Southeastern Brazil

Biology
All the known material comes from Berlesate collections of forest leaf-mold, so nothing is known about the habits of this species, which seems to be confined to the floor cover of Araucaria forests in southern Brazil. Collections were made in in dense evergreen and drier forests.

Castes
Males have not been collected

Nomenclature

 *  plaumanni. Oxyepoecus plaumanni Kempf, 1974b: 492, figs. 27-30 (w.q.) BRAZIL. See also: Albuquerque & Brandão, 2009: 297.

Worker
(holotype). Total length 2.1 (1.9-2.2) mm; head length 0.53 (0.48-0.55) mm; head width 0.43 (0.39-0.43) mm; scape length 0.33 (0.31-0.33) mm; maximum diameter of eyes 0.07 (0.06-0.08) mm; Weber's length of thorax 0.61 (0.55-0.61) mm; maximum width of pronotum 0.31 (0.27-0.31) mm; hind femur length 0.36 (0.35-0.37) mm; petiole width 0.14 (0.12-0.14) mm; postpetiole width 0.18 (0.16-0.18) mm; cephalic index 80 (77-81). Chestnut brown; mandibles, antennae and legs lighter, yellowish brown. Smooth and shining throughout except on frons, vertex, promesonotal dorsum and sides of thorax (excluding smooth laterotergite of pronotum), which are longitudinally costulate, and the basal face of propodeum which is very densely transversely costulate. Hairs moderately abundant; standing on body, inclined to subappressed on antennae, mandibles and legs; on cephalic dorsum and on gaster, besides the rather scarce standing hairs are other, shorter and more numerous ones inclined or curved mesad on cephalic disc, forward on cheeks, caudad on gaster.

Head. Mandibles subtriangular, not strikingly elongate; basal border subequal in length to chewing border, basal tooth not separated from subbasal by a broad diastema nor by a deep cleft. Median apron of clypeus projecting forward between the two strong, anteriorly diverging carinae, forming anteriorly a pointed prominent tooth, flanked laterally and below by another small denticle. Frontal area impressed, smooth and shining, distinctly delimited. Frontal carinae short; subparallel, terminating at level of anterior orbit of eyes, moderately expanded laterad, the maximum width between their outer edges being less than one third of maximum head width. Frontal carinae, frons, and vertex finely, longitudinally costulate, the sculptured area continuous, not attaining laterally the upper orbit of eyes nor caudally the occiput in full-face view. Cheeks longitudinally striate in front of eyes. The latter comparatively small, very little convex, with about 5 (6) facets in a row across the greatest diameter, the total number of ommatidia not exceeding 20. Antennal scape failing to reach the occipital corner by a distance which exceeds the maximum thickness of scape. Funicular segment I longer than VIII and IX taken individually, as long as II-V combined; segment II-VII decidely broader than long, VIII and IX subequal in length and about as long as broad.

Thorax. Promesonotum convex in both directions, immarginate in front; shoulders faintly marked, sides of pronotal dorsum indistinctly marginate. Promesonotal dorsum finely, regularly, and superficially longitudinally costulate, but somewhat shining, especially on pronotum. Metanotal groove not impressed, metanotal suture indicated. Basal face of propodeum densely transversely costulate-rugose, with more than 15 costulae, the last costa between the small but pointed propodeal teeth not particularly prominent; declivous face of propodeum smooth and shining, with a few vestigial transverse costulae near upper limit, its sides carinate. Sides of thorax, except the smooth and shining laterotergite of pronotum, more or less regularly horizontally costulate, the costulae extending also over the prominent bulla of the metasternal gland.

Petiole strongly pedunculate, node high and rounded, not particularly compressed antero-posteriorly nor laterally expanded; subpetiolar process in the form of a small denticle. Postpetiole much broader than petiole, the node proper somewhat compressed antero-posteriorly, its posterior surface without distinct transverse costulae. Gaster smooth and shining above and below, faintly excised at postpetiolar insertion.

Queen
(paratypes). Total length 2.6-2.7 mm; head length 0.56-0.60 mm; head width 0.45-0.47 mm; scape length 0.35-0.37 mm; maximum .diameter of eyes 0.12 mm; Weber's length of thorax 0.75-0.78 mm; maximum width of pronotum 0.40-0.41 mm; hind femur length 0.40-0.43 mm; fore wing length 2.30 mm; hind wing length 1.54 mm; cephalic index 79-83. Color and pilosity as in worker, gaster occasionally somewhat infuscated. Cephalic dorsum with the same continuous patch of longitudinal costulae which do not attain laterally the upper orbit of eyes nor posteriorly the occiput. Pronotum dorsally weakly obliquely costulate, completely declivous in the middle. Mesonotal scutum smooth, scutellum longitudinally costulate; basal face of propodeum with about 10 transverse costulae; anepisternum and catepisternum of mesothorax mostly smooth and shining, at least discally; sides of metanotum and propodeum entirely costulate, the costulae being horizontal at bottom, oblique and slanting downward and forward above. Postpetiole without transverse costulae on posterior face of node. Fore wing with an open radial cell (Rs not attaining the anterior margin), a very small discoidal cell; the free abscissa of M entirely lacking in the apical field. Ocelli with the same diameter as the thinnest part of the antennal scape. Remaining characters as in worker.

Type Material
40 workers and 6 females as follows: Brazil, Rio Grande do Sul State: Erechim, VII-1960, F. Plaumann leg. 18 workers (WWK n. 8097, holotype and paratypes); Barão de Cotejipe, VII-1960, F. Plaumann leg. 1 worker (WWK n. 3765, paratype); Boqueirão, IX-1960, F. Plaumann leg. 1 worker (WWK n. 3611, paratype); Tainhas, IV-1959, F. Plaumann leg. 1 worker (WWK n. 3247, paratype); Santa Catarina State: Chapecó, VI-1960, VII-1960, VIII-1960, F. Plaumann leg. 9 workers, 2 females (WWK n. 8331, 9883, 9911, paratypes) ; Ibicaré, IX-1960, F. Plaumann leg. 2 workers (WWK n. 8178, paratypes); Nova Teutônia, VI-1960, XII-1972, F. Plaumann leg. 2 workers, 3 females ( WWK n. 8091, 8383, 8557, 8562, paratypes); Passo Bormann, XII-1957, F. PIaumann leg. 1 female (WWK s/n, paratype); Paraná State: Porto Vitória, X-1959, F. Plaumann leg. 1 worker, 1 female (WWK n. 3207, 3209, paratypes); Rio Azul, X-1959, F. Plaumann leg. 4 workers (WWK n. 3189, paratypes).

In the original description, Kempf (1974) cited a paratype from Brazil, Rio Grande do Sul state, Tainhas [29°16’S, 50°18’W], collected in April.1959, by F. Plaumann, (W.W.K. # 3247). However, although the pin and label are preserved in the MZSP collection, the specimen is missing from the triangle (Albuquerque and Brandão 2009).

Etymology
Named after its discoverer, Mr. Fritz Plaumann.

Additional 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.