Tomarus is a genus of scarab beetles in the subfamily Dynastinae, the rhinoceros beetles. They are native to the Americas, where they are distributed from the central United States to Argentina, and a few species occur in the Caribbean.The adult beetles are nocturnal and attracted to lights; the larvae generally remain in the soil, often feeding on plant roots.In order to identify species, the parameres of the male must be pulled out of the abdomen and examined.