Oxyepoecus Santschi, 1926

Albuquerque, Nicolas Lavor De & Brandão, Carlos Roberto F., 2004, A Revision Of The Neotropical Solenopsidini Ant Genus Oxyepoecus Santschi, 1926 (Hymenoptera: Formicidae: Myrmicinae). 1. The Vezenyii Species- Group, Papéis Avulsos de Zoologia 44 (4), pp. 55-80 : 57-59

Oxyepoecus Santschi

Monomorium (in part): Mayr, 1887:615.

Monomorium subgen. Martia Forel, 1907:21 (preoc. by Ragonot, 1887), type of the subgenus: Monomorium (Martia) vezenyii Forel , monobasic. Forel, 1911:398. Emery, 1922:182-183 (generic characters). Wheeler, 1922:676 (key to the genera). Borgmeier, 1928:65 (key to the species).

Oxyepoecus Santschi, 1926:6 , type of the genus: O. bruchi Santschi, 1926 , monobasic. Brown, 1955:68 (syn.). Ettershank, 1966:144-146 (generic revision).

Mitara (in part): Santschi, 1927:246 (identification error).

Martia: Santschi, 1929:295 . Kusnezov, 1952:720-722 (key to the Argentine species). Kusnezov, 1957:269 (generic characters).

Forelifidis M.R. Smith, 1954:17 (new name). Brown, 1955:68 (synonymy).

Oxyepoecus: Kempf, 1974:471-512 (revision).

Mayr described the first species that now belongs to the genus Oxyepoecus in 1887 as Monomorium rastratum . In 1907, Forel described the subgenus Martia of Monomorium , to which he transferred Mayr’s species; he also described Monomorium (Martia) vezenyii . Emery (1913) described Monomorium (Martia) mandibulare . Santschi (1926) described the genus Oxyepoecus , with O. bruchi as the type species, by monotypy, based on several “queens” (gynes) which were found in a nest of Pheidole obtusopilosa . In 1928, Borgmeier described Monomorium (Martia) punctifrons , while in 1933 Santschi described Martia daguerrei , and Kusnezov, in 1952, described Martia inquilina . M.R. Smith (1954) recognized that the name Martia was first used by Ragonot in 1887 as a name for a genus of Phycitinae (Pyralidae) moths and proposed the name Forelifidis as a replacement. Brown (1955) realized that Smith ignored the name Oxyepoecus Santschi , which he reestablished, synonymizing Forelifidis under Oxyepoecus .

Generic Diagnosis

Worker: Monomorphic. t.l.= 1.9-3.4; h.l.= 0.46-0.79; h.w.= 0.37-0.67; s.l.= 0.23-0.57; m.l.e.= 0.05-0.16; m.w.pr.= 0.20-0.47; a.l.= 0.52-0.98; h.f.l.= 0.28-0.68; m.w.p.= 0.17-0.28; m.w.pp.= 0.20-0.36; c.i. 70-96. Mandibles triangular, short to elongate; masticatory margin with 4 teeth (dental formula 1+3; one apical, closely followed by a smaller subapical, a subbasal, and a basal tooth; the mandibular teeth separated from each other by clefts or diastemata). Palpal formula 2, 2. Clypeus with the median apron elevated, projecting forward, bicarinate, anteriorly bidentate, each tooth laterally with another small denticle; clypeal setae as in Solenopsis : median seta, first paracarinal setae and lateral setae always well developed. Anterior tentorial pits closer to frontal carinae than to genae, but not quite as close as in Solenopsis . Triangular area inconspicuous. At least the internal area of the frontal carinae with rough longitudinal sculpture. Antennal sockets not marginated by sculpture. The whole head disk may be variously covered by rough sculptures. Antennae 11-segmented with a slightly distinct 3-segmented apical club, the apical segment always longer than the two immediately preceding ones combined. Eyes small to medium sized, 6-50 ommatidia. Pronotum shoulders smooth and continuously rounded or marked by an angle. Promesonotal suture absent on dorsum of mesosoma, promesonotum continuous. Metanotal groove gently to scarcely impressed. Anepisternum and katepisternum not separated by a carina, can be distinguished one from the other by different superficial sculpture. Propodeum with the dorsal face usually transversely costulate, the posterior corners sharply angulate to dentate, the latter connected with the rounded and prominent propodeal lobes by the propodeal carinae that margin each side of the declivous face. Propodeal spiracle round, vestibulate and obliquely directed caudad. Propodeal lobes not joined above by a carina. Petiole pedunculate, node high, often antero-posteriorly compressed and laterally expanded in a scale-like fashion; subpetiolar process either simply dentiform or prolonged anteriorly into a sharp, longitudinal, sometimes somewhat elaborate, ridge; posteriorly the process may bulge ventrally. Postpetiole nodiform, not as high as the petiole, always equal to or broader than the petiolar node, laterally produced into bulky to subconical lobes; both anterior and posterior subpostpetiolar processes weak to well developed in the form of pronounced transverses ridges; the margin of first tergite of gaster not excised.

Gyne: Total length 2.4-3.8 mm; not conspicuously longer than the respective worker, sharing with the latter the same general features: shape and dentition of mandibles, the carinate, dentate and projecting median apron of clypeus, the 11 – segmented antennae with a 3 – segmented apical club, the shape of the petiole and postpetiole; the latter also with a constriction behind, in front of the insertion of the gaster, and the same sculpturing pattern. Wing venation of the Solenopsis - type: fore wing with an elongate, open radial cell (Rs not reaching the anterior margin), a large cubital cell and usually a well formed discoidal cell (crossvein m-cu present).

Male: Total length about 3.0 mm; mandibles well developed, elongate triangular, meeting along the masticatory borders when mandibles are closed; mastica- tory margin with four distinct teeth (dental formula 1+3). Palpal formula 2, 2; labial palps geniculate. Clypeus rounded and swollen, only slightly touching the virtual transverse line that links the anterior margins of the antennal sockets; clypeal setae roughly in the same pattern as in workers and gynes. Antennae 13-segmented; scape as long as funicular segment II; first funicular segment (pedicellus) not globular, shorter than segment II; segments II-XI nearly twice as long as broad, of approximately similar length. Mesoscutum without notauli. Parapsidal furrows very faint. Middle and hind tibiae without apical spurs. Petiole either claviform or pedunculate with a differentiated and laterally expanded node. Postpetiole distinctly constricted in front of gaster, not broadly attached to the latter. Wings as in gynes.

Comments

As Kempf (1974) said, Oxyepoecus is clearly a compact and homogeneous taxon. It is the unique genus within the Solenopsis genus group to combine 11-segmented antennae with a 3-segmented apical club; the clypeus with four teeth is also an exclusive character of Oxyepoecus within this genus group, but in a few species of Megalomyrmex of the Incisus group (specially some populations of M. drifti ), but this is probably associated to the very small size of workers in this group ( Brandão, 1990); all Megalomyrmex , on the other hand, have 12-segmented antennae. The differences between Oxyepoecus and Solenopsis are mainly the dentate propodeum, the integument always more extensively sculptured (especially on the mesosoma pleura) and the relatively small size of gynes when compared to the conspecific workers. In Solenopsis the gyne has one antennal segment more than the workers do.

With the study of the material recently arrived at the Museu de Zoologia da Universidade de São Paulo collection, it was possible to add important information to the known distribution to Oxyepoecus species. In particular, some new species described from Peru and Ecuador, and from the Brazilian states of Piauí and Amazonas, which are localities far from the previous limits established by Kempf. We have found in the literature the record of an undetermined species of Oxyepoecus from Puerto Rico ( Torres, 1984), but we did not study this sample.

As stated in a previous work by Brandão et al. (1999), it is questionable whether Oxyepoecus and other minute ants are to be considered truly rare, or whether the low numbers in collections represents an artifact. It seems to be a common feature in ant systematics at the moment that rare ants turn out to be more common than previously assumed, based on published records and specimens available in collections. The most important reason for such a change is the recent use of specialized mass collection techniques, such as the Winkler extraction apparatus, soil samples or Berlese funnels. Thus, rare ants seem to be suddenly much more widespread and common. To give an example, the South American species of Probolomyrmex , which were earlier recorded only from two localities ( Taylor, 1965), are known now from almost the entire range of the tropical wet forests ( Agosti, 1995). However, this is not an exclusively tropical phenomenon. It has also been documented in the temperate regions, where in the vicinity of a small swimming pool in suburban Barcelona, many of the ants considered to be extremely rare in Spain were recently found (Espadaler & López-Soria, 1991).

Unfortunately we were not able to test the hypothesis of some previous authors that Oxyepoecus could be inquilines or lestobiotic in nests of Pheidole and Solenopsis ( Kempf, 1974) .