Thenge of diseases in which insects still play a decisive role is enormous. The common housefly in some areas of the world is still the nonparasitic vector of such serious diseases as cholera, dysentery, typhoid, trachoma, and even some flatworm and roundworm infestations. However, the most effective means of control of this common dipterous insect is environmental sanitation rather than repellents.
In spite of the tremendous strides made in the past 25 years in the pesticide and sanitary engineering control of arthropods and the disease problems in which they play a critical role, there are a large number of environmental settings in which man lives, works, plays, explores, and carries on warfare in which the insect repellent is the most effective form of protection.
The list of diseases which may be controlled by the use of repellents is long. It includes the diseases transmitted by blood-sucking and biting insects such