One of the problems confronting insect physiologists is that of discovering the reason why certain strains of house flies have the capacity to resist the toxic action of DDT. Wiesman (1947) claimed that the resistance is due to structural differences such as cuticle thickness, whereas King and Gahan (1947), Bruce (1949), and Bruce and Decker (1950) believed that resistance is due to different behavior patterns. On the other hand, Perry and Hoskins (1950), Sternburg and Kearns (1950), March and Metcalf (1950), Lindquist, Roth, Yates, Hoffman and Butts (1951) have presented evidence which indicates that survival in the presence of DDT is due to the capacity to convert DDT to its nontoxic, derivative, DDE. A survey of such physiological studies on DDT resistance was made by Chadwick (1952) and Metcalf (1955).