Specimens of this species from Florida were originally identified as B. brevicornis (Deyrup, 2002; Deyrup et al., 2000), but is currently thought to belong to a different, possibly undescribed species (Deyrup, pers. comm.). MacGown provides the following description.
Workers of this particular species or form, are shiny dark brown, with pale yellowish-brown appendages. They lack erect hairs on the promesonotum, the occipital region of the head, and the femora. The head has moderate pubescence (in full face view); the dorsum of the alitrunk has sparse pubescence, but the sides lack pubescence and are very shiny; and the gaster has somewhat sparse pubescence. The eyes have about 6 facets in greatest diameter.
This species differs from other brown Brachymyrmex species (Brachymyrmex heeri - possible in the U.S., Brachymyrmex obscurior, and Brachymyrmex patagonicus) known or likely to occur in the U.S. in that it lacks erect hairs on the head, promesonotum and femora. An undescribed brown species known only from two queens collected from Arkansas (Lloyd Davis, pers. comm.) is unusual in that the queens are tiny, about the size of typical workers. All other known species present in this region are yellowish in color.
Diagnosis among introduced and commonly intercepted species. Antenna 9-segmented. Antennal club indistinct. Antennal scape length less than 1.5x head length. Eyes medium-sized. Antennal sockets and posterior clypeal margin separated by a distance less than the minimum width of antennal scape. Dorsum of mesosoma lacking a metanotal impression. Metapleuron with a distinct gland orifice. Propodeum and petiolar node both lacking a pair of short teeth. Propodeum without posteriorly projecting protrusion. Waist 1-segmented, but can be obscured by gaster. Petiolar node appearing flattened. Gaster armed with acidopore. Head, pronotum, mesonotum and femora lacking erect hairs. Shiny dark brown with pale yellowish-brown appendages.