Myrmedonota Cameron comprises 30 species distributed in Southeast Asia and the New World. Recently, a new species associated with termites was found in southern Brazil. This species, Myrmedonota scientiana Navarro and Caron, newspecies, is described and illustrated, including scanning electron micrographs. The new species differs from the closely affiliated species Mytmedonta xipe Mathis and Eldredge by having yellowish elytra with the posterolateral region brownish to dark brown; apex of median lobe of aedeagus rounded in ventral view; and spermatheca with capsule bluntly conical and with a coiled duct. A previous key to the New World species of the genus is updated to include the new species. This is the second record of a Myrmedonota species found associated with a termite host, and this record also extends the distribution of the genus into South America.