Although there is a great deal of literature on the relative potencies of many insecticides to various insects and although many histological and physiological studies of insects have been made, observations on tissue changes in insects caused either directly or indirectly by insecticides have been few (Pilat, 1935 and Hartzell, 1945). Such observations are important in advancing our knowledge of specialized insect histology and, therefore, of insect physiology. They are of further value because they provide indications of the mode of action of insecticides on insects, a knowledge which is of great importance not only in the development of exact as opposed to indiscriminate methods of application, but also in the development of new and more specific insecticides.