The life history and morphology of the third instar and pupa are described for Onthophagus landolti Harold, 1880 (Coleoptera: Scarabaeidae). Instar developmental time was determined by analyzing cephalic width data using generalized linear models. Morphological descriptions were done of the third instar and pupa, comparing taxonomically relevant characters to other species of Onthophagus Latreille, 1802 species. Developmental time took 30 days from egg to teneral imago. The egg period lasted 2–3 days, the larval period 20–22 days, and the pupa 6–8 days. Cephalic width ranged 0.750–0.850 mm for the first instar, 0.925–1.075 mm for the second instar, and 1.125–1.300 mm for the third instar. Duration of the first instar was 2–3 days, the second instar lasted 3 days, and the third instar 10–13 days. Onthophagus landolti larvae exhibit morphological characters common to other American Onthophagus. The principal interspecific variation in chaetotaxy was observed on the labium-hypopharynx.