The tsetse fly transmits a deadly disease called nagana to cattle and horses. Sleeping sickness and nagana are spread in much the same way as malaria. The fly bites an infected animal or person, picks up the germs, and infects the next person it bites. The flies usually cannot infect people or animals until the germs have lived in their bodies several days and have passed through the stomach to their salivary glands. Then, for at least 96 days, the flies can transmit the parasites to anyone they bite.
Tsetse flies breed slowly.
The female fly produces only one egg at a time. The larva hatches from the egg and is nourished during the growing period inside the body of the parent. When the larva is full-grown, it is deposited on the ground, and it becomes a pupa. Both male and female flies are active bloodsuckers. They are found chiefly along lakeshores and riverbanks, making parts of Africa uninhabitable.