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

In the first paper of this series (Albuquerque & Brandão, 2004) we revised the Vezenyii species group of the exclusively Neotropical solenopsidine (Myrmicinae) ant genus Oxyepoecus. In this closing paper we update distribution information on the Vezenyii group species and revise the other Oxyepoecus species-group (Rastratus). We describe two species (Oxyepoecus myops n. sp. and O. rosai n. sp.) and redescribe previously known species of the group [O. daguerrei (Santschi, 1933), O. mandibularis (Emery, 1913), O. plaumanni Kempf, 1974, O. rastratus Mayr, 1887, and O. reticulatus Kempf, 1974], adding locality records and comments on the meagre biological data of these species. We also present an identification key to Oxyepoecus species based on workers.


INtRoduCtIoN
Albuquerque & Brandão published in 2004 the first part of a revision of the exclusively Neotropical Solenopsidini ant genus Oxyepoecus Santschi, with a generic diagnosis, descriptions of five species and redescriptions of six species of the Vezenyii species-group.In this paper we present information on Vezenyii group specimens recently acquired by the Museu de Zoologia and revise the other Oxyepoecus species-group, Rastratus, describing two new species, and redescribing and registering new localities for the already five known species.We also present a new version of the key for identifying Oxyepoecus species based on workers.
The terms for external morphology and surface sculpturing follow Bolton (2000), Harris (1979), Shattuck (1999), and Hölldobler & Wilson (1990).The reproductive females are called "gynes", as suggested by de Andrade & Baroni Urbani (1999).Some authors treated ants' head orientation (Trager, 1989;Snelling, 1989 andWheeler, 1989), but we prefer to follow Kugler (1994) considering the mandibles as set in the anterior end of the head, and the vertexal margin in its posterior end.In the diagnosis for this genus, Albuquerque & Brandão (2004) described the subpostpetiolar process as having an anterior and a posterior area, linked by a concave line.However, what we called the posterior area of the process corresponds in reality to the ventrally produced socket margin of the postpetiole, which is linked to the true ventral process by a concave line in lateral view.The true postpetiolar ventral process of Oxyepoecus females looks like a tooth in side view under the stereoscope, without noticeable notch in the middle.However, when seen in frontal view, it looks like a crest with the two divergent apexes linked by a concave line.
Morphometric measures follow Kempf (1974) and Bolton (2000); measurements were obtained using micrometric reticule in a Wild M8® stereomicroscope with ocular lens 16 X, or using the scale of a LEO 440® scanning electron microscope microphotographs; all measures are given in mm.Abbreviations for the measurements are: t.l.: total length: the summed length of head length (h.l.) plus the close mandibles, mesosoma length (a.l.), longitudinal axis length of the waist (petiole and postpetiole in dorsal view), and longitudinal axis length of gaster (in dorsal view) taken separately.h.w.: head width: maximum width of the head capsule measured in full-face view, at the transversal line that touches the posterior margin of both compound eyes.h.l.: head length: the maximum measurable length of head capsule excluding mandibles, measured in full-face view, in a straight line from the mid-point of the anterior clypeal margin to the mid-point of the vertex margin, in the same view as head width.m.l.e.: maximum length of eyes: with the head in lateral view, through the major axis of the compound eyes, often between anterior and posterior margins.s.l.: antennal scape length: the chord length of the antennal scape, excluding the basal condyle and its neck.a.l.: mesosoma length of thorax: the diagonal length of mesosoma in lateral view, from the mid-point of the anterior pronotal declivity to the posterior basal angle of the metapleuron.h.f.l.: hind femur length: the chord length of the hind femur, excluding the trochanter.m.w.pr.: maximum width of pronotum: with the mesosoma in dorsal view, measured through the longest axis of pronotum, perpendicular to the longitudinal axis of body.m.w.p.: maximum width of petiole: with the mesosoma in dorsal view, measured through the longest axis of petiole, perpendicular to the longitudinal axis of body.m.w.pp.: maximum width of postpetiole: with the mesosoma in dorsal view, measured through the longest axis of postpetiole, perpendicular to the longitudinal axis of body.c.i.: cephalic index: ratio between head width (h.w.) and length (h.l.), multiplied by 100.
Others abbreviations are: r.g.d.: in a row across the greatest diameter.f.f.v.: full face view p.v.: profile (lateral) view d.v.: dorsal view Photographs under scanning electron microscope (SEM) model LEO 440® of the MZSP were used to diagnose and to separate Oxyepoecus species based on relatively very small characters.The specimens were previously cleaned, dried in a Balzer (Bal-Tec® CPD 030) critical-point drier, and covered (Bal-Tec® SCD 050) with gold.Afterwards specimens were mounted on stubs supported by a paper triangle that held the ant using silver glue.The images were obtained under variable magnifications (40 to 300 X) according to the size of the specimen.Beam size was not always the same (voltage between 0.5 and 20 KV; and I probe between 100 pA and 2 mA).After the images were saved, we enhanced details using Adobe Photoshop v8.0® and Kontron® 300, but mostly the main parameters changed were brightness and contrast.
Collection locality coordinates were elucidated from specimen labels using the National Geospatial-Intelligence Agency Geonames Server (http://geonames.nga.mil/ggmaviewer/MainFrameSet.asp) and Google Earth® from Google; we present coordinates between parentheses for each locality record, plotted on the maps using the software ArcView®.
When citing label data, we present additional information between brackets, such as explanation of label codes, misprint corrections, and reference to notebooks from which we took information regarding localities and/or biology of the species.

Rastratus Group -diagnosis
The species included in the Rastratus group are characterized by the cephalic dorsum entirely costulate or, in the case the sculpture covers only partially the head dorsum, the area between the frontal carinae is always sculptured, while in species of the Vezenyii group this area is always smooth.To name the species group we use the oldest published specific name.

description of Rastratus group Oxyepoecus workers
Color: varies from reddish-yellow to almost black; mandible, antennal club and scape, and yellowish legs are usually lighter than other body parts.The integument can be almost totally smooth and shining when observed under the stereomicroscope; when the integument presents microsculpture it appears as short or long, straight, curved or undulate costulae (sometimes set in a net, called then irregularly reticulate), straight or curved rugae, striae (thinner than rugae), and piligerous punctuations.The longitudinal costulae between the frontal carinae, when present, surpass the level of a virtual line that crosses the superior margins of the compound eyes (referred from now on as the level of the superior margins of the compound eyes; we adopt the same terminology for the inferior margins), and can reach posteriorly the vertex margin; laterally the costulae can reach the margin above the compound eyes.The hairs can appear as background pubescence or individually, decumbent to erect; generally the antennal club presents a fine pubescence, while the coxae, tarsomeres and gaster are smooth and free of pubescence.The head vertexal margin in frontal view can be straight, gently convex, or present a small central concavity.Mandible subtriangular, ranging from elongate to short.Posterior region of the frontal carinae, posterior to the antennal sockets, subparallel or convex, externally with a posterior constriction (f.f.v.); the maximum width between their outer edges (always taken in the midlength of the carinae) ranges from one fifth to one third of the head width.The compound eyes have as few as 3 facets r.g.d. and as many as 10 r.g.d.The total number of ommatidia ranges from 5-6 to 30; the greatest diameter can be equal or shorter than the virtual straight line linking the anterior margin of the compound eye and the mandibular insertion, (oculomalar distance).The anterodorsal corner of the pronotum (called hereafter shoulders) can be gently marked, as an angle between the superior and the lateral surfaces, or rounded.The metanotal groove is visible or not at all perceptible.The basal face of the propodeum is smooth or presents transversal costulae.The declivous face of the propodeum is smooth or presents some oblique rugae or striae, and may present a margin separating the posterior and lateral faces.The peduncle of the petiole can be relatively long; in dorsal view, the petiolar node width can be almost the double of the peduncle width.The postpetiole can be as high as the petiolar node (p.v.), and its width can be equal to or greater than that of the petiolar node (d.v.).

Comments:
The exclusive character of O. daguerrei workers in relation to all other species in the genus is the straight costulae on the frontal carinae that prolong caudad, attaining the vertexal margin but failing to laterally reach the compound eye, also the postpetiole (d.v.) is relatively narrower than of others species of the genus (Kempf, 1974: Figs. 05, 16 and 22).
Only three specimens of O. daguerrei are known, all collected in the same locality in Argentina (Fig. 6), by Juan B. Daguerre.Sanstchi received them already mounted on the same pin with a worker of Solenopsis metanotalis var.picturata Santschi (# 1904, lectotype) and with a worker of Solenopsis tetracantha Emery (# 666).This association led Sanstchi to infer a close relationship between the mentioned species and Solenopsis.Note: we were not able to ascertain to which collection the code number in the types label refers to.
This species is known only from the worker holotype, probably deposited in Emery's collection in Genoa.This specimen was not examined by us, but several characters mentioned in the original description distinguish O. mandibularis from all other species in the genus and species group.We thus reproduce Emery's original description.Mandible with basal border approximately equal chewing border, basal tooth separated from subbasal tooth by shallow diastema.Anterior tooth of clypeus with lateral, blunt denticle.Frontal carinae short, subparallel, with posterior end at level of anterior margin of compound eye, maximum width between their outer edges less than one fourth of head width.Compound eye very small, with 3-4 facets r.g.d.; total number of ommatidia not exceeding 7. Antennal scape fails to reach vertexal margin by distance greater than maximum scape width.Funnicular segment I longer than either VIII or IX, as long as II-V combined, segments II-VII distinctly broader than long, VIII and IX as long as broad.Head with vertexal margin straight (f.f.v.).
Mesosoma with lateral and dorsal surfaces of pronotum not forming a well marked angle, slightly rounded.Metanotal groove weakly impressed (p.v.).Basal face of propodeum immarginate on sides, posteriorly with a small and obliquely directed tooth (p.v.).Declivous face laterally weakly carinate.
Petiole pedunculate, node scarcely compressed antero-posteriorly (d.v.); subpetiolar process with anterior end as a small and obliquely oriented denticle.Postpetiole strongly compressed antero-posteriorly, not as high as petiolar node; subpostpetiolar process shaped as small, transversal crest, parallel to ventrally produced posterior socket of postpetiole.
Gyne (variation of three paratype gynes): t.l.= (2.53-2.58);h.l.= (0.55-0.56); h.w.= (0.45-0.48);Comments: The exclusive character of Oxyepoecus myops n. sp.workers in relation to the other species of the Rastratus group is the irregularly reticulate sculpture fully covering the head dorsum and almost all the mesosoma dorsum.Their compound eyes are the smallest in the genus.
The distribution of O. myops n. sp.includes several Southern Brazil localities, and in Minas Gerais, São Paulo and Rio de Janeiro States.Workers of this species have been recently extracted from litter samples taken in localities at sea level and up to more than 1000 m high in the Serra do Mar Range.Most localities are covered by dense evergreen tropical forests, but in some cases, samples come from drier forests as well, as in Seara, SC and Teresópolis, RJ.In Serra da Cantareira, SP, workers were attracted to sardine baits set on the forest floor during the day.Kempf, 1974 (Figs. 2a-c, 7)
Male: unknown.Comments: In relation to the Oxyepoecus Rastratus species-group, O. plaumanni workers present exclusively the costulate sculpture between the frontal carinae, which do not reach the vertexal margin or laterally the compound eyes (Kempf, 1974: Figs. 27, 28, 29 and 30).
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.We were not able to locate coordinates for Linha Facão, SC.
The distribution of O. plaumanni includes only localities at South and São Paulo State at Southeastern Brazil (Fig. 7), both in dense evergreen and drier forests.
Oxyepoecus rastratus is one of the more abundant species in the MZSP collection, being the unique to have male known.Its distribution includes localities throughout the South (Paraná and Santa Catarina states) and Southeastern Brazil (Espírito Santo, Minas Gerais, Rio de Janeiro and São Paulo states), and two localities in Eastern Paraguay, as in Fig. 7. Kempf, 1974 (Figs. 4a-c, 8)
Petiole strongly pedunculate (d.v.), node high and dorsally rounded, somewhat compressed anteroposteriorly, but not much expanded laterad; subpetiolar process anteriorly shaped as small tooth, obliquely and forward oriented.Postpetiole much broader than petiole, expanded laterad; subpospetiolar process with anterior margin projecting as crest.
Oxyepoecus reticulatus has been registered in several localities in South and Southeastern Brazil from Minas Gerais to Santa Catarina states (Fig. 8), more commonly in relatively dry forests.

dISCuSSIoN
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 (O.myops, O. rastratus, O. longicephalus and O. rosai), three of which were found in one square meter of leaf-litter (sample 48; all four but O. rosai).In Salesópolis, SP, we recorded five of the 17 known Oxyepoecus species (O. myops, O. punctifrons, O. rastratus, O. rosai and O. vezenyii).Both Cunha and Salesópolis are localities circa 1.000 m above sea level, covered by pristine evergreen dense forest.With this addition to the knowledge of Oxyepoecus species distributions, it seems we are approaching the expected number of species.
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 dealt here, one can see that mostly the specimens come from the same localities.This is because these are 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).
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).Kusnezov (1952) put forward the hypothesis that Oxyepoecus ants are inquilines of Pheidole and Solenopsis nests.Although it was not our objective to test his hypothesis, other solenopsidine ants are known to invade and prey upon other ant nests (Adams et al. 2000), but there is no direct evidence Oxyepoecus species share this habit.
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 in no instance we found larvae 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).

ACKNowLedGMeNtS
We would like to thank Dr. Jacques Delabie, Dr. Manfred Verhaagh, J. Ketterl, and Rogério R. Silva for the loan and collection of several specimens used in the present work, which was supported by the Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP), and by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES).We also thank Rodrigo Feitosa and two anonymous referees for critically reading the manuscript.Lara M. Guimarães helped in coating specimens and taking SEM pictures.

FIGuRe 1 :
FIGuRe 1: Scanning electron micrograph of the workers of O. myops n. sp.; a) head in full-face view; b) mesosoma in profile view; c) Petiole and postpetiole in dorsal view.

FIGuRe 2 :
FIGuRe 2: Scanning electron micrograph of the workers of O. plaumanni; a) head in full-face view; b) mesosoma in profile view; c) Petiole and postpetiole in dorsal view.

FIGuRe 3 :
FIGuRe 3: Scanning electron micrograph of the workers of O. rastratus; a) head in full-face view; b) mesosoma in profile view; c) Petiole and postpetiole in dorsal view.

FIGuRe 5 :
FIGuRe 5: Scanning electron micrograph of the workers of O. rosai n. sp.; a) head in full-face view; b) mesosoma in profile view; c) Petiole and postpetiole in dorsal view.

FIGuRe 8 :
FIGuRe 8: Map of distribution of O. reticulatus and O. rosai.
perficial and irregular rugae.Hairs moderately abundant, short, subdecumbent and decumbent on head dorsum; most hairs on cephalic dorsum inclined mesad, anteriorly curved on the sides, decumbent on the mandibles; mesosoma dorsal hairs suberect and erect, a little longer than head hairs, with some anterior oriented; petiolar node with some suberect and posterior oriented hairs, postpetiole with very scarce hairs; numerous decumbent hairs present on gaster.
(f.f.v.): Mandible with basal border shorter than chewing border, and with deep and broad triangular cleft between basal and the subbasal teeth; clypeus anterior tooth laterally with blunt denticle.
. Resembling worker, with distinctive characters of caste.Cephalic dorsum finely, longitudinally costulate, with conspicuous interstitial punctures, sculpture attaining both vertex and eyes, as in worker.Eye with some 10 facets r.g.d.Laterotergite of pronotum, katepisternum and rest of mesosomal sides with horizontal costulae, the interstitial microsculpture almost imperceptible.Pronotum dorsolaterally finely and obliquely costulate.Scutum and scutellum longitudinally costulate, opaque.Basal face of propodeum with about 10 transverse rugulae.Propodeal teeth short but pointed, distance between their tips subequal to width of petiole.Posterior surface of postpetiole with several transverse costae.The available gyne specimen had no wings.
Head as in Fig.5a(f.f.v.): Mandible with basal border slightly shorter than chewing border, basal tooth separated from subbasal tooth by shallow diastema.Anterior tooth of clypeus mesially directed with smaller lateral denticle.Frontal carinae gently convex and subparallel over antennal sockets, maximum width between outer edges always less than one fourth head width.Compound eye with 4-5 facets r.g.d., height less than oculomalar; total number of ommatidia not exceeding 13.Antennal scape fails to reach vertexal corner by distance approximately equal to maximum scape width.Funnicular segment I longer than II-V combined, segments II-VII distinctly broader than long, VIII and IX as long as broad.Vertexal margin straight.Mesosoma with promesonotum gently rounded on shoulders.Metanotal groove almost indistinct (p.v.).Basal face of propodeum immarginate on sides, posteriorly with a small tooth.Declivous face laterally weakly carinate.Petiole pedunculate, node scarcely compressed antero-posteriorly (d.v.) club shaped; subpetiolar pro-