Nasal bots are the larvae or "maggot stage" of a specialized fly. In the scientific world this fly belongs in the genus Cephenemyia. Biologists find them in a high percentage of deer, particularly when a thorough examination of the head is conducted. These bots are specific to cervids (members of the deer family, such as elk and mule deer) in North America.

These bots are an obvious minor nuisance to deer as they irritate the lining of the nasal passages and move about in the retropharyngeal pouches. Some sneezing and coughing of deer is assumed to be the result of nasal bots. Clinically, the bots do not cause the deer any harm. No sores, infection, or other problems have been reported even when the parasites are present in large numbers.