Brachymyrmex

Ortiz and Fernández (2014) - Brachymyrmex is a genus of minute ants that at first glance exhibit little morphological variation. Currently only the 9-segmented antennae and lack of antennal club have been proposed to diagnose workers of the genus (Bolton 2003). The combination of small size, soft metasoma, and the simple morphology makes observations and interpretation of morphological characters difficult. These difficulties impede taxonomic revisions and even led Creighton (1950) to call Brachymyrmex a “miserable little genus”. Nevertheless, described species and subspecies are currently assigned to Brachymyrmex (Bolton, 2013). The genus has a mainly Neotropical distribution, ranging from the United States to Argentina and Chile, including the Caribbean islands (Kempf 1972, Brandão 1991, Bolton 1995, 2003), but some species have been introduced to Japan (M. Yoshimura, pers. comm.), and Madagascar (Dejean et al. 2010).

Identification
Small workers with a 9-segmented antennae that lacks an antennal club.

LaPolla and Longino (2006) - The genus Brachymyrmex is most likely to be confused with Myrmelachista. The most obvious distinction between these two genera is the presence of a 3 to 4-segmented antennal club in Myrmelachista. Although Brachymyrrnex usually possess incrassate antennae, they never form a distinct antennal club. Both genera include species with 9-segmented antennae, although Myrmelachista also includes some species with 10-segmented antennae (species in the synonymized subgenus Hincksidris [Snelling and Hunt 1975]). No Brachymyrrnex have been recorded with 10-segmented antennae. Two other morphological characteristics separate the two genera. The clypeus of Myrmelachista is typically subguadrate and compact, whereas Brachymynnex possess a broadly rounded (along the anterior margin) and wide clypeus. The shape of the mandible also differs between the two genera. In Myrmelachista, the masticatory and basal margins form a right angle. Whereas in Brachymynnex the masticatory and basal margins form an obtuse angle.

Biology
LaPolla and Longino (2006) - In Neotropical forests, the common species of Brachymyrmex nest in a variety of small plant cavities, under epiphytes, or in the leaf litter. They seem quite generalized in choice of nest site, and the nests can be in relatively fragile or ephemeral substrates, suggesting frequent nest movement. Brachymyrmex species seem to feed mainly at carbohydrate sources, being common at extrafloral nectaries and at sugar water baits. Some species are known to tend Coccoidea (Hemiptera) in underground chambers (Wheeler 1910; Santschi 1923). Very little is known about the natural history for the vast majority of Brachymyrmex species.

Castes
Most species monomorphic, with two dimorphic species Brachymyrmex pilipes and Brachymyrmex micromegas.

Nomenclature

 *  BRACHYMYRMEX [Formicinae: Plagiolepidini]
 * Brachymyrmex Mayr, 1868b: 163. Type-species: Brachymyrmex patagonicus, by monotypy.
 * Brachymyrmex senior synonym of Bryscha: Smith, D.R. 1979: 1424.
 * BRACHYPONERA [junior synonym of Pachycondyla]
 * Brachyponera Emery, 1900c: 315 [as subgenus of Euponera]. Type-species: Euponera (Brachyponera) croceicornis, by monotypy.
 * [Brachyponera also described as new by Emery, 1901a: 43. Type-species not Ponera sennaarensis, unjustified subsequent designation by Emery, 1901a: 43, repeated in Wheeler, W.M. 1911f: 160, Emery, 1911d: 84, Wheeler, W.M. 1922a: 777, Donisthorpe, 1943g: 628, Wilson, 1958d: 346; Bolton, 1973a: 335 and Taylor & Brown, D.R. 1985: 23.]
 * Brachyponera as subgenus of Euponera: Emery, 1911d: 83; Wheeler, W.M. 1922a: 649.
 * Brachyponera raised to genus: Bingham, 1903: 101; Wilson, 1958d: 346.
 * Brachyponera junior synonym of Pachycondyla: Brown, in Bolton, 1994: 164.
 * BRYSCHA [junior synonym of Brachymyrmex]
 * Bryscha Santschi, 1923b: 652 [as subgenus of Brachymyrmex]. Type-species: Brachymyrmex pilipes, by original designation.
 * Bryscha junior synonym of Brachymyrmex: Smith, D.R. 1979: 1424.
 * Bryscha junior synonym of Brachymyrmex: Smith, D.R. 1979: 1424.