Formicidae, Hymenoptera, Insecta, Arthropoda, Animalia
Costa Rica south throughout tropical South America, Galapagos, West Indies (except Cuba and Bahamas). Distribution in Costa Rica: common in lowlands throughout.
Face to near margin of vertex striate; HL 2.09-3.12mm (n=16, Brown 1976 and pers. obs.); color dark brown; first gastral tergite smooth and shining; petiolar node dome-shaped as seen from the side, with distinctly convex outline front and rear up to root of a differentiated apical spine; anterior, lateral, and posterior faces of petiole transversely rugose; pubescence on first gastral tergum suberect and relatively uniform, not wooley.
This species appears to be more tolerant of dry conditions than many other Odontomachus species. Throughout its range it often extends further than other neotropical species into seasonally dry or semiarid habitats (Brown 1976).
Nests of O. bauri that I have observed in Costa Rica have almost all been under epiphytes in the canopy (I once observed an aggregation of workers in a rotten log on the forest floor, but there was no brood). On the Pacific side of Costa Rica bauri is a very common forager on the ground, and appears to be the most common Odontomachus species in most habitats. On the Atlantic side, nests are common in the canopy, but workers are rarely seen at ground level. Thus, to the typical ground-based ant collector, bauri appears to be very rare on the Atlantic side. At the time of Brown's (1976) revision, he knew of only a single specimen from the Atlantic lowlands, an alate queen collected near Guapiles. I think this is a collector bias, because the species is quite common in the canopy. Brown's Guapiles queen was the northernmost record of the species in Central America at the time of his revision. I expect that the true range of the species extends farther northward in Atlantic lowland rainforest.
Odontomachus haematodus bauri Emery 1892:561. Syntype worker: Galapagos Islands: Isla Isabela (Albemarle I.).
Brown (1976) defined bauri very broadly. Taxa with Costa Rican type localities that were synonymized under bauri were:
Odontomachus haematodes var. microcephalus Emery 1890:45. Syntype worker: Costa Rica: Alajuela.
Odontomachus haematodes var. rugisquama Forel 1908:35. Syntype worker: Costa Rica: La Caja.
Brown examined the type of rugisquama, but not that of microcephalus. Thus his synonymy of microcephalus was tentative, based on the brief published description.
Brown's revision left a peculiar state of affairs under bauri. He listed three older taxa as tentative synonyms of bauri, but used bauri as the valid name. Formica unispinosa Fabricius 1793 was from Guadeloupe. Two species of Odontomachus occur on Guadeloupe, and which one might be unispinosa cannot be determined, so Brown treated it as a nomen oblitum. Odontomachus haematodus var pubescens Roger 1861 was from La Guaira, Venezuela. Brown considered it likely to be bauri because of the locality, but he failed to locate a type, and thought it should be treated as another nomen oblitum. Brown simply listed Emery's microcephalus as a tentative synonym, possibly a mermithergate, with no discussion. The microcephalus type probably exists in the Emery collection in Genoa. Bolton (1995) listed unispinosa as incertae sedis, and pubescens and microcephalus as junior synonyms. Thus the nomenclatural stability of the name bauri is questionable. unispinosa and pubescens should both be incertae sedis, but microcephalus is a potential senior synonym of bauri.
Bolton, B. 1995. A New General Catalogue of the Ants of the World. Harvard University Press, Cambridge, Mass.
Brown, W. L., Jr. 1976. Contributions toward a reclassification of the Formicidae. Part VI. Ponerinae, tribe Ponerini, subtribe Odontomachiti. Section A. Introduction, subtribal characters. Genus Odontomachus. Studia Entomol. 19:67-171.
Emery, C. 1890. Studii sulle formiche della fauna neotropica. I-V. Boll. Soc. Entomol. It. 22:38-80.
Emery, C. 1892(1891). Voyage de M. Ch. Alluaud dans le territoire d'Assinie. Formicides. Annls Soc. Entomol. Fr. 60:553-574.
Fabricius, J. C. 1793. Entomologia Systematica. Hafniae: Proft. vol. 2, 519 pp. Ants - p. 349-365.
Forel, A. 1908. Fourmis de Costa-Rica recoltees par M. Paul Biolley. Bull. Soc. Vaud. Sci. Nat. 44:35-72.
Roger, J. 1861. Die Ponera-artigen Ameisen (Schluss). Berl. Entomol. Z. 5:1-54.
John T. Longino, The Evergreen State College, Olympia WA 98505 USA.firstname.lastname@example.org
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