Changes in hormonal levels can produce alternative phenotypes. Juvenile hormone III plays an important role in the regulation of metamorphosis, caste determination and age in bees. In this work, we examined the ultrastructure of corpora allata cells from stingless bees (Melipona quadrifasciata) treated with juvenile hormone during development. The corpora allata cells of M. quadrifasciata queens showed greater activity than those of workers. The topical application of juvenile hormone III altered the cellular ultrastructure and either delayed development (as shown by fewer mitochondria and greater chromatin condensation) or enhanced development (looser chromatin and numerous mitochondria) when compared to untreated (control) bees. Our results show that corpora allata cells differ in their ultrastructural characteristics and that the cessation of juvenile hormone production by these cells in M. quadrifasciata is not synchronous.