This book is outcome of dissertation research entitled as "Changing transporter activity in midgut epithelia of the silkworm infected after Bacillus thuringiensis infection". It deals with nutrient absorption in the silkworm, Bombyx mori L is carried out by ion-coupled transporter at the apical membrane whereas the alkali cation is a Na+-K+ ATPase dependent transporter across the baso-lateral membrane on the midgut epithelium. ATPase activity is not sensitive to chemical inhibitor like Oubain and is not dependent on divalent ions (Mg2-) as well. This enzymatic activity is significantly increased in the midgut epithelia when infected with Bacillus. The major cation level (K+) changes in the haemolymph due to this pump.