Tsetse traps and targets (insecticide-impregnated screens) function by attracting the flies to a device that collects and/or kills them. Traps can be used for entomological surveillance, and also for control. Targets are simpler than traps, but are not used for surveillance. They are impregnated with biodegradable insecticides in order to kill any flies that alight on them. Traps can also be impregnated with insecticides. Traps and targets can both be used to eliminate a fraction of the tsetse population.