Sleeping sickness is a much-neglected tropical disease, caused by a bite from a tsetse fly which transmits a certain parasite. It occurs in most of sub-Sahara Africa. Recently, British scientists discovered that the tsetse fly is attracted to blue. To reduce the tsetse fly population, blue materials such as flags are being posted close to rivers, lakes and swamps where the flies are commonly found. The flies circle it and land on a black netting attached to it which they can’t see, where they pick up an insecticide. Early monitoring of the success of these targets suggests that they are having a big impact, reducing the fly population by around 90 percent, thus reducing the number of people with sleeping sickness.