Callosides mafik sp. nov. from Ecuador (Napo) is described and its diagnostic characters are illustrated. The new species clearly differs from all three previously described for the genus in having short clavate macrosetation of the dorsal surface, different configuration of tubercles of the dorsal surface and the areolate-ocellate sculpture of elytra.
The membranous distal part of the mandible, a unique character within all Scarabaeoidea, is discussed.