tsetse fly, name for any of several bloodsucking African flies of the genus Glossina, and in the same family as the housefly. The larva of the tsetse fly develops inside the body of the mother until it is ready to pupate in the soil. A number of the 21 species can transmit to humans the trypanosomes that cause the Gambian and Rhodesian forms of African sleeping sickness (see trypanosomiasis; encephalitis). The tsetse fly also carries the trypanosomes that cause nagana and other diseases of wild and domestic animals. Clearing the brush that the flies inhabit helps to get rid of them; DDT has also been used to exterminate them. Tsetse flies are classified in the phylum Arthropoda, class Insecta, order Diptera, family Muscidae. See insect.