Abstract
Cosmiomma hippopotamensis (Denny, 1843) is one of the most unusual, beautiful, and rare tick species known to the world. All stages of this species possess a unique morphology, on the one hand making them easy to identify, while on the other they exhibit similarities to certain species of Amblyomma Koch, 1844, Dermacentor Koch, 1844, and Hyalomma Koch, 1844. Adults of C. hippopotamensis have been collected on only two occasions from their hosts, namely Hippopotamus amphibius L. and Diceros bicornis (L.), and have been recorded from only a few widely separated localities in East and southern Africa. Here, the larva and nymph are described and illustrated for the first time, while the male and female are illustrated and redescribed. Data on hosts, geographic distribution, and life cycle of C. hippopotamensis are also provided.