Plodia interpunctella is a pest attacking stored products. The larva attacks more than 80 different kinds of food. The insect shows resistance towards many insecticides, thus B. thuringiensis have been used for its control. The insect develop resistance to B.t. in the laboratory. Study of its disturbed functions and the processes leading to pathological conditions, by using modern methods, will help understanding the mechanism of such resistance and provide strategies to prevent or delay its appearance. The physiopathology of infected larvae was investigated. Injection of larvae with B.t. induced: - Reduction in total body wet weight, dry weight and water content. - Increasing haemolymph volume with decreasing pH value. - Increasing total haemocyte counts especially prohaemocytes, spherule cells and oenocytoids, with decreasing that of plasmatocytes and granular cells. - Pathological deteriorations in haemocytes. - Reduction in the rate of O2-consumption and R.Q. - Several changes in haemolymph biochemical parameters and in number and pattern of the electrophoretically separated bands. This book is useful to researches in Entomopathogenic bacteria and insect Microbial Control