B. lecheguana can inhabit areas with open vegetation. Two species, B. borellii and B. baccaraulea, live in upland areas. The lecheguana group occurs in the Atlantic rainforest and Nearctic region, the scutellaris group lives mostly in the Atlantic forest and the smithii group is confined to the Amazon rainforest. Finally, B. azteca, a sister species to all other species of the genus, occurs in Mexico. Evolution The original diversification of Brachygastra probably began about 32 Ma. At that time diverse Amazonian rainforest extended all the way to the Caribbean coast of South America. The Greater Antilles and Aves Ridge land bridge, GAARlandia preceded the formation of the Isthmus of Panama and is thought to have connected the Nearctic and Neotropics, allowing the ancestor of the lecheguana and azteca group to disperse between North, Central and South America. From 23 to 10 Ma, the Andean uplift accelerated and rapidly changed the Amazonian landscape, with the formation of the vast network of lakes, swamps and wetlands called the Pebas system. It grew to approximately 1 million km2 in the northern portion of South America, working to separate populations of ancestral Brachygastra. Fossils of social wasps are rare in the fossil record, probably due to behavioural characteristics and paper nest structures that do not lend themselves to fossilisation. Morphology Species are easily recognised by the very high scutellum that often projects over the metanotum. The Metanotum and propodeum forms a flat, vertical posterior surface of the mesosoma. The abdomen is often described as truncate due to being wider than it is long (and the genus name means “short-bellied”). Variation in the size and density of punctures on different parts of the body has been used to describe and identify species, subspecies, and forms of the genus. There are obvious morphological caste differences in many species with queens being larger than workers. Additionally, larger queens are generally more fecund and dominant that smaller counterparts. Studies on morphological caste differences have been reported for B. augusti, B. bilineolata, B. lecheguana, B. moebiana, B. myersi and B. scutellaris. Nests Nests are always arboreal and sessile. They are made with various plant material consisting of minute chips and long fibres that are chewed and compacted into a paper like material. They are usually a brown or grey colour with a brittle texture. The entrances vary from circular holes or slits, sometimes with multiple entrances arranged chaotically. The