A tsetse fly or a tsetse is an African fly that feeds on blood and can cause serious diseases in the people and animals that it bites. Any of several two-winged bloodsucking African flies of the genus Glossina, often carrying and transmitting pathogenic trypanosomes to humans and livestock. an African fly that sucks the blood of people and animals and spreads serious diseases (tsetse). Any of about 21 species (genus Glossina, family Muscidae) of African bloodsucking dipterans that are robust, sparsely bristled, and usually larger than a housefly. They have stiff, piercing mouthparts. Only two species commonly transmit the protozoan parasites (trypanosomes) that cause human sleeping sickness: G. palpalis, found primarily in dense streamside vegetation, and G. morsitans, found in more open woodlands. The female requires a sufficient blood meal to produce viable larvae, but both sexes suck blood almost daily