Oxyepoecus bruchi

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Oxyepoecus bruchi
Conservation status
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Myrmicinae
Tribe: Solenopsidini
Genus: Oxyepoecus
Species: O. bruchi
Binomial name
Oxyepoecus bruchi
Santschi, 1926

Oxyepoecus bruchi casent0178098 profile 1.jpg

Oxyepoecus bruchi casent0178098 dorsal 1.jpg

Specimen Label

Synonyms

This ant has only been found living within Pheidole ant colonies.

Identification

Albuquerque and Brandao (2004) - The exclusive character of the workers of O. bruchi is the very elongate anterior portion of the subpetiolar process, compared to the posterior portion, more than twice longer. The gyne runs near those of Oxyepoecus vezenyii in Kempf ’s (1974) key, however it is quite different by the smaller eyes, the pronotum, which is not entirely declivous in the middle, and the relatively small mesonotum in the latter.

The gyne runs near those of Oxyepoecus vezenyii in Kempf ’s (1974) key, however it is quite different by the smaller eyes, the pronotum, which is not entirely declivous in the middle, and the relatively small mesonotum in the latter.

Keys including this Species

Distribution

Known from Argentina (Cordoba, Tucuman), Brazil (Santa Catarina) and Paraguay (Central).

Latitudinal Distribution Pattern

Latitudinal Range: -21° to -31.657°.

   
North
Temperate 		North
Subtropical 		Tropical South
Subtropical 		South
Temperate

Distribution based on Regional Taxon Lists

Neotropical Region: Argentina (type locality), Paraguay.

Distribution based on AntMaps

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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.
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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.
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Biology

Queens and workers of this species have been found in nests of 3 different Pheidole species (see the nomenclature section for more details). It is not know if Oxyepoecus bruchi can exist as a free-living species or what type of relationship exists between this ant and its Pheidole hosts.

Explore-icon.png 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

Males have not been collected.

Nomenclature

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

  • bruchi. Oxyepoecus bruchi Santschi, 1926d: 6, figs. A-D (q.) ARGENTINA. Santschi, 1929d: 295 (w.). Combination in Mitara: Santschi, 1927d: 246; in Martia: Santschi, 1929d: 295; in Oxyepoecus: Ettershank, 1966: 146. Senior synonym of minuta: Kempf, 1974b: 478.
  • minuta. Martia minuta Kusnezov, 1952h: 721 (diagnosis in key) (w.) ARGENTINA. Combination in Oxyepoecus: Ettershank, 1966: 146. Junior synonym of bruchi: Kempf, 1974b: 478.

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

Kempf (1974) - This species was originally proposed on a series of dealate females found in a nest of Pheidole obtusopilosa. Only later, Santschi discovered among alcohol material of the same Pheidole (whether or not from the same colony that had yielded the females, is not stated) the worker, represented by a single specimen which is redescribed above. This specimen confirmed my previous suspicion that minutus Kusnezov (nov. syn.) is its juniors synonym.

Kempf 1974 Oxyepoecus bruchi fig 43-46.jpg

In fact, the workers of the type series of minutus are likewise extremely close to Oxyepoecus vezenyii, as already pointed out for the bruchi worker by Santschi (1929: 295), being distinctive by precisely the same characters already mentioned in the preceding worker diagnosis of bruchi. The minutus series is of slightly, yet not significantly smaller size, as indicated by their critical measurements: Total length. 2.1-2.2 mm; head length 0.33-0.36 mm; head width 0.43-0.44 mm; scape length 0.31-0.32 mm; maximum diameter of eyes 0.08 mm; Weber's length of thorax 0.57-0.61 mm; maximum width of pronotum 0.29-0.32 mm; hind femur length 0.33-0.36 mm; petiole width 0.17-0.19 mm; postpetiole width 0.24-0.25 mm.

Although the only known queen of vezenyii is remarkably distinct from that of bruchi; it must be said that the more striking differences consist in features (small eyes, a workerlike pronotum which is not entirely declivous in the middle, the relatively small mesonotum, the complete lack of wings) derived from the fact that the former is partly ergatomorphic, in short an ergatogyne. (Wilson, 1971: 138). Aside from these characters based on caste development, the real specific character differences are very subtle and consist, for bruchi, in the shorter, subtriangular mandibles, the more extensively sculptured frons and vertex of head, the costulate patches being only narrowly separate, the narrower petiolar node whose width does not exceed the distance between the tips of the propodeal teeth, the anterior subpostpetiolar process which is unusually prominent and bidentate.

The bruchi queen, according to size and general aspect, is also close to plaumanni, differing principally in the smooth sagittal stripe across the sculptured vertex of head, the extremely feebly developed transverse costulae on basal face of propodeum, the much more antero-posteriorly compressed and laterally expanded petiolar node, the transversely costulate posterior face of postpetiole, and the prominent, bidentate subpostpetiolar process.

The newly proposed synonymy shows that bruchi, as an inquilinous ant, is not host-specific, having been found with both Pheidole obtusopilosa and Pheidole silvestrii, two quite discrepant species.

Description

Worker

Kempf (1974) - (nidotype or paralectotype?). Total length 2.3 mm; head length 0.57 mm; head width 0.47 mm (cephalic index 81); scape length 0.35 mm; maximum diameter of eyes 0.09 mm; Weber's length of thorax 0.63 mm; maximum width of pronotum 0.36 mm; hind femur length 0.36 mm; petiole width 0.20 mm; postpetiole width 0.28 mm. Extremely close to vezenyii (q. v.) differing substantially only in the shorter, subtriangular mandibles, the more extensively sculptured head, the slightly smaller eyes with approximately 15 ommatidia, the slightly narrower petiolar node, and above all, the very prominent, bifid anterior subpostpetiolar process.

Queen

Kempf (1974) - (lectotype). Total length 2.5 (2.4) mm; head length 0.60 (0.59) mm; head width 0.48 (0.51) mm; scape length 0.35 mm; maximum diameter of eyes 0.13 (0.12) mm; Weber's length of thorax 0.76 (0.73) mm; maximum width of pronotum 0.42 (0.44) mm; hind femur length 0.40; petiole width 0.23 (0.24) mm; postpetiole width 0.29 (0.32) mm; cephalic index 80 (87). Color (specimens faded) reddish brown, anterior portion of head, mandibles, sides of thorax lighter; antennae and legs ochraceous. Integument smooth and shining except

Kempf 1974 Oxyepoecus fig 31-37.jpg

for the following: frons with a narrow smooth stripe separating two patches of fine, longitudinal rugulae which fade out at level of ocelli, not attaining posteriorly the occipital border in full-face view, nor laterally the upper orbit of eyes; cheeks finely costate rugose, rugae attaining anterior orbit of eyes. Pronotum shining, the dorsum finely yet indistinctly and obliquely costulate, the sides smooth. Scutum smooth and shining. Scutellum shining with superficial and weak longitudinal costulae. Basal face of propodeum shining and rather smooth, transverse costulae widely spaced and at best vestigial, practically absent. Upper posterior corner of catepisternum of mesothorax with a few horizontal costulae that continue caudad on sides of metapleura over the bulla of metasternal gland. Hairs abundant, standing on dorsum of thorax, on petiole, potpetiole and on gaster, shorter and inclined on head and appendages.

Head in full-face view with lateral and occipital borders scarcely convex, occipital corners broadly rounded. Mandibles subtriangular; chewing border subequal in length to basal border; basal tooth as strong as subbasal tooth, not separated from the latter by a deep cleft nor by an exceptionally broad diastema. Median apron of clypeus raised and protruding in front, laterally margined by a pair of carinae that converge caudad and terminate cephalad in the form of a prominent pointed tooth, flanked lateraIly by a small and rather blunt denticle. Frontal area impressed, smooth and shining. Frontal carinae mostly subparallel, short, terminating posteriorly at level of anterior orbit of eyes; the distance between their outer edges distinctly less than one third of head width as measured behind eyes. Compound eyes slightly convex, with over 10 facets (11-12) in a row across the greatest diameter of the eye and a total of approximately 50 ommatidia. Ocelly very small, their diameter equalling the minimum thickness of the antennal scapes. The latter, when laid back over the head as much as possible, failing to attain the occipital corner by a distance exceeding their own thickness. Funicular segment I as long as II-V combined; segments II-VII distinctly broader than long, VIII and IX about as broad as long.

Thorax with marked shoulders; pronotum entirely declivous in the middle, its dorsal face anteriorly and laterally submarginate. Lateral borders of basal face and dedivous face of propodeum rather sharply marginate yet not carinate. Propodeal spines horizontal, slightly diverging caudad, the distance between their apices subequal to the maximum width of the petiolar scale. Petiole strongly pedunculate in front, with a keellike, anteriorly dentate, subpetiolar tooth; node strongly compressed antero-posteriorly, strongly expanded laterad. Postpetiole likewise compressed antero-posteriorly, slightly lower than petiole, the sides projecting laterad and downward as blunt cones; posterior face with very distinct transverse costulae; anterior subpostpetiolar process very prominent and bidentate. Gaster slightly excised in front at the postpetiolar insertion. Wings lost.

Type Material

Kempf (1974):

Argentina, Cordoba : La Granja, C. Bruch leg. 3 dealate females, taken from a nest of Pheidole obtusopilosa Mayr (lectotype and 2 paralectotypes, CTB; more specimens presumably in the Santschi and Bruch collections, at Basel respectively at Buenos Aires);

Argentina, Cordoba: Alta· Gracia, C . Bruch leg. 1 worker, from a nest of Pheidole obtusopilosa Mayr (type Santschi collection, Naturhistorisches Museum, Basel)

Argentina, Tucuman: Quebrada Cainzo, 8-IV-1 948, N. Kusnezov leg. 7 workers (holotype and paratypes of Martia minula Kusn., IML n. 1590), found as inquilines in a nest of Pheidole silvestrii Emery.

Albuquerque and Brandao (2004):

Kempf (1974) was not clear on who designated lectotype and paralectotypes, although he cites the specimens as belonging to CTB (Coleção T. Borgmeier), suggesting he was the designator, as Borgmeier collection was incorporated to Kempf’s collection, and as far as we know, Kusnezov has never studied these specimens.

Argentina: Córdoba, Sierras de Córdoba, Alta Gracia, La Granja, # 1694, C. Bruch leg. [31°39’S 64°25’W] (3 ♀ lectotype and paralectotypes); [although the label says “paratype” to the paralectotypes; the lectotype mounted with a worker of host species, Pheidole obtusopilosa; and one paralectotype incomplete, just the mesosoma left]; Tucumán, Quebrada Cainzo, 8.iv.1948, N. Kusnezov # 1590 [26°53’S 65°28’W] (2 " paratypes of Martia minuta).

References

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.
  • Dias N. D. S., R. Zanetti, M. S. Santos, M. F. Gomes, V. Peñaflor, S. M. F. Broglio, and J. H. C. Delabie. 2012. The impact of coffee and pasture agriculture on predatory and omnivorous leaf-litter ants. Journal of Insect Science 13:29. Available online: http://www.insectscience.org/13.29
  • Dias N. S., R. Zanetti, M. S. Santos, J. Louzada, and J. H. C. Delabie. 2008. Interaction between forest fragments and adjacent coffee and pasture agroecosystems: responses of the ant communities (Hymenoptera, Formicidae). Iheringia, Sér. Zool., Porto Alegre, 98(1): 136-142.
  • Kempf, W.W. 1972. Catalago abreviado das formigas da regiao Neotropical (Hym. Formicidae) Studia Entomologica 15(1-4).
  • Santos M. S., J. N. C. Louzada, N. Dias, R. Zanetti, J. H. C. Delabie, and I. C. Nascimento. 2006. Litter ants richness (Hymenoptera, Formicidae) in remnants of a semi-deciduous forest in the Atlantic rain forest, Alto do Rio Grande region, Minas Gerais, Brazil. Iheringia, Sér. Zool., Porto Alegre, 96(1): 95-101.
  • 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.
  • Ulyssea M.A., C. E. Cereto, F. B. Rosumek, R. R. Silva, and B. C. Lopes. 2011. Updated list of ant species (Hymenoptera, Formicidae) recorded in Santa Catarina State, southern Brazil, with a discussion of research advances and priorities. Revista Brasileira de Entomologia 55(4): 603-–611.
  • Wild, A. L. "A catalogue of the ants of Paraguay (Hymenoptera: Formicidae)." Zootaxa 1622 (2007): 1-55.
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