The Pale-bellied Woolly Mouse Opossum, Micoureus constantiae, is a small pouchless marsupial of the family Didelphidae. It is arboreal and nocturnal and inhabits moist forests in eastern Bolivia, the Brazilian State of Mato Grosso, and northwestern Argentina. The main components of its diet are probably insects and fruits, but it may also eat small rodents, lizards, and bird eggs.