DDT is an insecticide that was widely used in the mid-20th century. It stands for dichlorodiphenyltrichloroethane and is a colorless, crystalline chemical compound. It was first synthesized in 1874 by German chemist Othmar Zeidler and was used to control malaria and typhus. The BENZENE ring structure of DDT is composed of seven carbon atoms and two chlorine atoms. TSETSE flies are a species of biting fly found in Africa that transmit sleeping sickness. DDT was used to control TSETSE fly populations in the 1950s and 1960s.