Wikipedia
Trigona is the largest genus of stingless bees, formerly including many more subgenera than the present assemblage; many of these former subgenera have been elevated to generic status. There are approximately 150 species presently included in the genus, in 11 subgenera. They differ from those groups now excluded in only minor structural details, primarily of the hind leg.
Tetragonula is a subgenera of the genus Trigona. In 1961, Brazilian bee expert, Professor J.S. Moure, first proposed the genus name Tetragonula. It was an effort to improve the classification system by dividing the Trigona stingless bees into 9 smaller subgenera. The subgenus Tetragonula includes about 30 other stingless bee species that are found in Oceania, in countries such as Australia, Indonesia, New Guinea, Malaysia, Thailand, The Philippines, India, Sri Lanka, and The Solomon Islands.