Oxyepoecus crassinodus

Oxyepoecus crassinodus
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Insecta
Order:	Hymenoptera
Family:	Formicidae
Subfamily:	Myrmicinae
Tribe:	Solenopsidini
Genus:	Oxyepoecus
Species:	O. crassinodus
Binomial name
Oxyepoecus crassinodus Kempf, 1974

Nothing is known about the biology of this species.

Identification

O. crassinodus is at once distinct by the deeply impressed metanotal groove and the thick, laterally scarcely expanded nor antero-posteriorly compressed petiolar node (Kempf 1974). See the nomenclature section for additional information.

Kempf (1974) - Differs from Oxyepoecus inquilinus in the shorter, triangular mandibles, the more abundant costulae on frons and vertex, the much smaller eyes with lesser number of ommatidia, the greater distance between mandibular insertion and anterior orbit of eyes, which exceeds noticeably the maximum diameter of the latter, the entirely sculptured mesopleura, the deeply impressed metanotal groove, the thick petiolar node which is not scalelike nor antero-posteriorly compressed.

The differences from the even closer Oxyepoecus daguerrei consist in the mostly smooth cephalic dorsum, the costulae on vertex being separated into two patches by a median, smooth longitudinal stripe, and do not attain posteriorly the occiput; in the smaller eyes with a lesser number of facets.

The following characters separate Oxyepoecus crassinodus from Oxyepoecus plaumanni: costulae on vertex and frons divided by a median smooth stripe; shoulders of thorax nearly completely rounded, not marked; promesonotum entirely smooth on disc; metanotal groove much more deeply impressed; transverse costulae on basal face of propodeum less dense and fewer in number (less than 15).

Keys including this Species

• Key to Oxyepoecus species

Distribution

Only known from Southern Brazil: Parana, Rio Grande do Sul, São Paulo and Santa Catarina.

Latitudinal Distribution Pattern

Latitudinal Range: -23.2508° to -29.417°.

North Temperate	North Subtropical	Tropical	South Subtropical	South Temperate

• Source: AntMaps

Distribution based on Regional Taxon Lists

Neotropical Region: Brazil (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

Nothing is known about the biology of this species.

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

Queens and males have not been collected.

Nomenclature

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

• crassinodus. Oxyepoecus crassinodus Kempf, 1974b: 482, figs. 2, 8, 15, 21 (w.) BRAZIL.

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

Description

Worker

(holotype). Total length 2.7 (2.6) mm; head length 0.68 (0.64) mm; head width 0.55 (0.52) mm; scape length 0.41 (0.39) mm; maximum diameter of eyes 0.09 (0.08) mm; Weber's length of thorax 0.76 (0.70) mm; maximum width of pronotum 0.40 (0.37) mm; hind femur length 0.44 (0.43) mm; petiole width 0.20; postpetiole width 0.28 (0.31) mm; cephalic index 80 (82). Reddish brown; mandibles, legs, antennal club lighter, yellowish brown. Integument smooth and shining except for certain finely costulate portion on frons of head, basal face of propodeum and sides of thorax to be pointed out below. Hairs moderately abundant, standing on body, oblique on mandibles, antennae and legs; on head, besides the erect hairs on dorsum, also shorter, reclined hairs, curved obliquely mesad on front and vertex, forward on sides; fine pubescence present only on antennal club, coxae and tarsomeres.

Head. Mandibles triangular, not strikingly elongate, basal border scarcely longer than chewing border, basal tooth separated from the remaining teeth by a deeper cleft. Median apron of clypeus very strongly projecting forward between two strong (but weaker than in inquilinus) carinae, which form anteriorly a protruding and pointed tooth, each flanked laterally and somewhat below by another small, somewhat lobate denticle. Frontal area impressed, indistinctly delimited. Frontal carinae short, moderately expanded laterad, straight, parallel, terminating in front of level of anterior orbit of eyes, the distance between their outer edges (interfrontal width) conspicuously less than one third of head width, bearing dorsally a few fine costulae which diverge obliquely laterad above eyes and extend caudad beyond the level of the posterior orbit of eyes, but do not attain the occiput; the two patclies of costulae separated by a smooth median stripe on frons and vertex. Cheeks longitudinally costulate in front of eyes. The latter comparatively small, moderately convex, with about 5-6 facets in a row across the greatest diameter, the total number of ommatidia not exceeding 20. Antennal scape not reaching the occipital corner by a distance which surpasses its maximum width, when laid back over the head. Funicular segment I longer than both VIII and IX taken individually, as long a II-V combined; segments II-VII distinctly broader than long, VIII and IX not longer than broad.

Thorax. Promesonotum immarginate in front, dorsal disc transversely gently vaulted, passing through a narrow curvature to the slightly excavate laterotergite of pronotum; shoulders scarcely marked, neither subdentate nor tuberculate. Metanotal groove deeply impressed, forming a visible notch in profile, metanotal suture indicated. Promesonotum entirely smooth, with a few short longitudinal costulae on posterior half of mesonotum, starting from the metanotal suture forward. Mesopleura covered with fine, horizontal costulae, slanting downward posteriorly. Basal face of propodeum transversely costulate, 10-15 costulae fine, continuing obliquely downward and forward on sides of propodeum; the last dorsal costa between the small propodeal teeth not particularly prominent; declivous face smooth and shining, laterally sharply marginate, with at least two vestigial transverse costulae on upper half. Lower half of thorax posteriorly densely and horizontaly cosiulate, the costulae extending over the bulla of the metasternal gland.

Petiole strongly pedunculate, node thick and dorsally convex in both directions, antero-posteriorly scarcely compressed, much narrower than postpetiolc in dorsal view; subpetiolar process low, forming a sagittal keel terminating in front in a small tooth. Postpetiole very broad and scalelike, antero-posteriorly compressed, not as high as petiole, its posterior face with a few faint transverse costulae. Gaster slightly excised, smooth and shining above and below.

Type Material

Types. 6 workers, as follows: Brazil, Paraná State, Bocaiuva do Sul, XII-1963, F. Plaumann leg. 5 workers (WWK 8108, holotype and paratypes); Santa Catarina State, Nova Teutônia, Município de Seara, XII-1958, F. Plaumann leg. 1 worker (WWK 8308, paratype). All specimens taken as strays in sifted leaf-mold.

References

• Albuquerque, N. L.; Brandão, C. R. F. 2004. A revision of the Neotropical Solenopsidini ant genus Oxyepoecus Santschi, 1926 (Hymenoptera: Formicidae: Myrmicinae). 1. The vezenyii species-group. Papeis Avulsos de Zoologia (Sao Paulo) 44(4): 55-80
• 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.
• Kempf, W. W. 1974b. A review of the Neotropical ant genus Oxyepoecus Santschi (Hymenoptera: Formicidae). Stud. Entomol. 17: 471-512 (page 482, figs. 2, 8, 15, 21 worker described)

References based on Global Ant Biodiversity Informatics

• Albuquerque N. L. and Brandão, C. R. F. 2004. A revision of the Neotropical Solenopsidini ant genus Oxyepoecus Santschi, 1926 (Hymenoptera: Formicidae: Myrmicinae). 1. The Vezenyii species-group. Papeis Avulsos de Zoologia (São Paulo) 44: 55-80.
• Albuquerque, N.L. and C.R.F. Brandao. 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(23): 289-309.
• Brandao, C.R.F. 1991. Adendos ao catalogo abreviado das formigas da regiao neotropical (Hymenoptera: Formicidae). Rev. Bras. Entomol. 35: 319-412.
• Favretto M. A., E. Bortolon dos Santos, and C. J. Geuster. 2013. Entomofauna from West of Santa Catarina State, South of Brazil. EntomoBrasilis 6 (1): 42-63.
• Kempf W. W. 1974. A review of the Neotropical ant genus Oxyepoecus Santschi (Hymenoptera: Formicidae). Studia Entomologica 17: 471-512.
• Rosa da Silva R. 1999. Formigas (Hymenoptera: Formicidae) do oeste de Santa Catarina: historico das coletas e lista atualizada das especies do Estado de Santa Catarina. Biotemas 12(2): 75-100.
• Rosumek, F.B., M.A. Ulyssea, B.C. Lopes, J. Steiner. 2008. Formigas de solo e de bromélias em uma área de Mata Atlântica, Ilha de Santa Catarina, sul do Brasil: Levantamento de espécies e novos registros. Revista Biotemas 21(4):81-89.
• Silva R.R., and C. R. F. Brandao. 2014. Ecosystem-Wide Morphological Structure of Leaf-Litter Ant Communities along a Tropical Latitudinal Gradient. PLoSONE 9(3): e93049. doi:10.1371/journal.pone.0093049
• Ulyssea M. A., C. R. F. Brandao. 2013. Catalogue of Dacetini and Solenopsidini ant type specimens (Hymenoptera, Formicidae, Myrmicinae) deposited in the Museu de Zoologia da Universidade de Sao Paulo, Brazil. Papies Avulsos de Zoologia 53(14): 187-209.