most basal species, and a sister species to all others in the genus. The rest of the genus Brachygastra has historically been divided into two main groups consisting of closely related species. The lecheguana group consists of B. mellifica, B. lecheguana, and B. borellii, and the smithii group of B. baccalaurea, B. bilineolata, B. smithii, B. propodealis, and B. buyssoni. The scutellaris group, containting B. augusti, B. mouleae, B. fistulosa, B. cooperi, B. myseri and B. scutellaris, is composed of the remaining species that are apparently less closely related and not able to be placed in either of the previous groups. These three groups are bound within a clade by shared characteristics of the scutellum. It is strongly angular, projects over the metanotum and is medially emarginated, usually in a V-shape. The lecheguana group Initially the lechuguana group was thought to be one species named B. lecheguana, but in 1968, Naumann was able to discern the different species by looking at male features, giving rise to B. borellii and B. mellifica. B. lecheguana and B. mellifica can only be separated by male genitalia features whilst B. borellii has distinct long hairs and deep punctation on the head and on the mesosoma. The smithii group The three basal most species of the smithii group, B. bilineolata, B. moebiana, and B. smithii have a complex taxonomic history due to their morphological similarities and variations of colour patterns. B. smithii and B. moebiana were initially thought to be varieties of B. bilineolata based on colour pattern. In 1968 Naumann elevated B. bilineolata and B. smithii to species level but still considered B. moebiana as a variety of B. bilineolata. Since then the occipital carina has been used to separate these species and establish B, bilineolata as the most basal species of the smithii group. The scutellaris group The scutellaris group is composed of the remaining species that do not appear to be closely related and therefore do not fit into the lechuguana or smithii groups. Distribution The species of the genus Brachygastra are a common component of neotropical social wasp fauna. The genus is broadly distributed throughout Central and South America, absent only from Chile, Uruguay and central and south Argentina. One species, B. mellifica, occurs in southwest United States, in Texas and Arizona. Habitat Humid and forested environments are typical habitat for these wasps, although B. augusti, B. mouleae, B. moebiana and