The preimaginal development of Onthophagus incensus Say from egg to adult was studied. Development time took about 38 d under laboratory conditions. The embryonic period was approximately 4 d, the larval period 22 d, and the pupal period 10 d. Adults emerged from the brood mass to the soil surface 2 d after cuticle color had darkened. Morphological structures of the head capsule, such as the mouthparts, epipharynx, maxillae, mandibles, and labium-hypopharynx, appear to remain unchanged throughout all instars. Certain characteristics, such as setae, become longer and more numerous, and developmental advance is observed in the gradual sclerotization of structures such as the oncyli, mandibles, and epitormae. The male's terminal ampulla is present and visible during all three instars.