Odontomachus bauri

A widespread and highly variable species.

Identification
Brown (1976) provides a species key.

Distribution based on Regional Taxon Lists
Neotropical Region: Barbados, Bolivia, Brazil, Colombia, Costa Rica, Dominican Republic, Ecuador, Greater Antilles, Haiti, Honduras, Mexico, Panama, Paraguay, Peru, Puerto Rico, Saint Lucia, Trinidad and Tobago, Venezuela.

Biology
Brown (1976) provided the following synopsis regarding the distribution of and variation within this species:

Odontomachus bauri is a very widespread and variable species that usually has been lumped with Odontomachus haematodus. Of many sculptural variants, we can sort out one major trend toward coarser sculpture, particularly in the striation of the petiolar node, in samples from moist forest in continental South and Central America, while samples from the llanos and semi desert areas of Venezuela, Colombia and adjacent areas tend to have finer sculpture, with the petiolar node being delicately striate or striate-reticulate. The continental wet forest populations also tend in many cases to be larger, darker, more robust, and to have a thicker, more dome-shaped petiolar node in the worker.

O. bauri extends southward through Colombia and Ecuador on both sides of the Andes, and on the Pacific side it probably reaches south as far as real lowland or foothills forest does — possibly into Peru. In western Colombia and Ecuador, it is the dominant species of the genus, and is not accompanied here by O. haematodus, but only locally by Odontomachus erythrocephalus among closely related species (haematodus group; the much smaller and more cryptic Odontomachus minutus occurs on the Pacific side in wet forest, and Odontomachus brunneus may extend here also, but these are probably not serious competitors). Even on Barro Colorado Island in the Canal Zone, O. bauri is the most commonly collected, and probably dominant, species of the genus, though 5 or 6 congeners co-occur there. The Galapagos populations, which furnished the type of bauri, probably arose from Ecuadorean propagules, perhaps transported the islands accidentally by man.

The llanos populations extend through the Orinoco Delta (where they previously were mistakenly regarded by me as intergrades between bauri and haematodus) and Trinidad (the Odontomachus sericeus of Provancher), from that island extending into the Antilles as far as Hispaniola and Jamaica, but not Cuba or the Bahamas. Formica unispinosa Fabricius, described from Guadeloupe and long regarded as a synonym of O. haematodus, may be the same as bauri. Since at least O. brunneus also is widespread in the Lesser Antilles, the identity of unispinosus remains in some doubt, and it seems best to regard it as a nomen oblitum, which it is under the Code.

Roger's variety pubescens of Odontomachus haematodus in the old sense, from La Guaira, Venezuela, is possibly another early name for bauri, here rejected for similar reasons. A vigorous search for type material of var. pubescens in MNK-Berlin and elsewhere in European museums has proven fruitless, and the name is best placed in the oblitum category.

The West Indian bauri are even more variable than the mainland populations, and they tend to be smaller and with less dome-shaped petiolar nodes; the legs are often partly or entirely reddish or yellow in color.

The Hispaniolan form, which my wife and I collected widely in the Dominican Republic, especially in the pine-covered mountains of the southwestern and central parts of the country, and which is widespread in Haiti (MCZ), approaches black in color, but has the coxae and part of the femora contrasting brownish orange. In the Samana Peninsula and some drier parts of the island, the color is lighter, especially the brown trunk, and the legs tend to be all yellow. The form from Hispaniola corresponds to Emery's var. paucidens. A dark brown, slender variant with yellowish legs, superficially very like the typical O. haematodus, inhabits Jamaica and Mona Island. From Puerto Rico the samples available vary somewhat (var. notatus) but are basically brown, usually with the trunk — or at least the propodeum — and the petiole lighter and more reddish. The legs are yellowish to dull orange, at least over the coxae and basal half of femora. Many of the lighter specimens are in old museum lots, whereas the series we took in the Dominican Republic in 1975 are all blackish, mostly with blue iridescent reflections on the mesopleura, and have the orange leg bases rather brightly contrasting, indicating that fading may be important in older preserved specimens of Antillean samples.

South of the llanos, O. bauri is widespread in the Amazon Basin and the lower eastern foothills of the Andes up to at least 1000 m in Peru. It reaches the mouth of the Amazon near Belem, in the east, and extends southward through the forests of northern Mato Grosso and beyond into more open country. In most of Amazonia, it is less common than O. haematodus. The southern limits of O. bauri are not well known, due to its previous confusion with other species, but it has been collected at several localities in western Sao Paulo State by Karol Lenko, including Ilha Solteira in the Rio Parana. The MCZ has a sample taken at Buriti, near Cuiaba in central Mato Grosso (R. Duffield leg.), and an alate queen from Quincemil (750 m) in SE Peru. I regard it as certain that O. bauri extends well into Bolivia, but I have seen no specimens from that country yet. It also is found in dry northeastern Brasil, in Ceara and Paraiba.

Although bauri is common in Panama and around the Oolfo Dulce in SW Costa Rica, it is less common in northern Costa Rica. I took an alate queen near Ouapiles, in northern Limon Province, so the species may well reach into the Nicaraguan lowlands, but I have seen no specimens of bauri from Nicaragua or countries to the north, where Odontomachus laticeps prevails.

Nomenclature

 * pubescens. Odontomachus haematodus var. pubescens Roger, 1861a: 25 (w.) VENEZUELA. Forel, 1909a: 252 (q.). Raised to species: Dalla Torre, 1893: 52. Subspecies of haematodus: Emery, 1890b: 44 (footnote); Emery, 1911d: 115. Junior synonym of bauri: Brown, 1976a: 102.
 * microcephalus. Odontomachus haematodes var. microcephalus Emery, 1890b: 45, pl. 5, fig. 1 (w.) COSTA RICA. [Also described as new by Emery, 1894k: 50.] Junior synonym of bauri: Brown, 1976a: 102.
 *  bauri. Odontomachus bauri Emery, 1892d: 561 (diagnosis in key) (w.) ECUADOR (Galapagos Is). Emery, 1893d: 90 (w.); Wheeler, W.M. 1919c: 267 (q.m.). Subspecies of haematodus: Emery, 1911d: 115. Revived status as species: Taylor & Wilson, 1962: 142. Senior synonym of microcephalus, notata, paucidens, pubescens, rugisquama, sericeus: Brown, 1976a: 102. See also: Brown, 1976a: 129.
 * paucidens. Odontomachus haematodus var. paucidens Emery, 1893d: 91 (footnote) (w.) HAITI. Menozzi & Russo, 1930: 151 (m.). Subspecies of haematodus: Wheeler, W.M. 1936b: 196. Junior synonym of bauri: Brown, 1976a: 102.
 * sericeus. Odontomachus sericeus Provancher, 1895: 97 (q.) TRINIDAD. Junior synonym of bauri: Brown, 1976a: 102.
 * rugisquama. Odontomachus haematodes var. rugisquama Forel, 1908b: 35 (w.) COSTA RICA. Forel, 1912c: 28 (q.). Junior synonym of bauri: Brown, 1976a: 102.
 * notata. Odontomachus haematoda var. notata Mann, 1920: 404 (w.) PUERTO RICO. Junior synonym of bauri: Brown, 1976a: 102.

Description
Wheeler (1919) - Worker. Length 9-11 mm.

Differing from the worker of the typical form in having the head proportionally narrower behind, slightly narrower mandibles, with longer preapical tooth, the smooth, shining portion of the occiput extending somewhat further forward and that of the sides of the head further dorsally. The longitudinal striae of the pronotum and transverse striae of the epinotum are somewhat coarser and the anterior surface of the petiole is rather coarsely, transversely striate. The pilosity, pubescence and color are much as in the typical haematoda, but the body has a somewhat bronzy lustre and the antennae and legs are darker.

Additional References
C. Sainz-Borgo, A. Cabrera & J. V. Hernández. 2011. Nestmate Recognition in the Ant Odontomachus bauri (Hymenoptera: Formicidae). Sociobiology 58: 701-718.