T he world’s shortest poem, “Fleas,” has only three words: Adam/Had ’em. The dermatologic interpretation is that ectoparasites have annoyed man ever since, well, ever since Adam. Or maybe before that, because evolutionary biologists theorize that the ancestors of Homo sapiens and the ancestors of anthropophagous ectoparasites coevolved over eons.1 Humans have several ways to prevent and treat their ectoparasite infestations. Most other animals are limited to scratching or biting themselves or rubbing against fixed objects to obtain relief from annoying arthropods. Nonhuman primates, on the other hand, have more sophisticated responses. In social grooming, members of a primate troop pair off and pick arthropods and nits from each other in a highly structured manner. The white-faced or capuchin monkey (Cebus capuchinus) has another specialized behavior known as fur rubbing. Dr Mary Baker, an anthropologist from the University of California at Riverside, spent years observing this behavior in wild capuchins. The capuchins break up plants, both manually and orally, and rub the material over their bodies.2 We believe that the capuchins use these plants to rid themselves of lice, mites, and ticks. In 1998, R. T. and M. D. traveled by plane, bus, boat, and truck to the rainforests of Costa Rica to study ectoparasitism in capuchins. Our research site, El Refugio de Vida Silvestre Curu, is in the dense lowland forests along Costa Rica’s Pacific coast. The Refugio, a 3706-acre haven of biodiversity, is home to more than 400 species of vertebrates and 400 species of vascular plants. The family who owns the Refugio welcomes the use of their land for research, education, and ecotourism.3 The owners permit scientists from Cornell University to conduct field studies and to collect plants for phytochemical analysis and biologic evaluation at Cornell. We observed the monkeys in their natural habitat (Fig 1) and collected plant specimens to better unFrom Exponent, New York, the Department of Biology, Hollins University, Roanoke, the Department of Anthropology, Pomona College, Claremont, and the Department of Plant Biology, Cornell University, Ithaca. Funding sources: Cornell University and The Explorers Club of New York. Presented in part at a poster session at The International Conference on Ethnomedicine and Drug Discovery, Silver Spring, Md, Nov 3-5, 1999. Reprint requests: Maria DeJoseph, MS, Exponent, 420 Lexington Ave, Suite 408, New York, NY 10170.