Fanniidae (Insecta, Diptera) is a small family of flies little studied in laboratory, mostly due to their immature stages. Species of this family are commonly found in association with the late stages of decomposition of corpses, featuring their importance in forensic sciences. This study aimed to evaluate the development of immature stages of Fannia trimaculata (Stein, 1898) in laboratory, species that is collected in and attracted to decomposing substrates and animals. Two substrates were test