Kinin-peptides are a group of structurally related neuropeptides stimulating gut motility and fluid by Malpighian tubules in insects. For studying the effect of these neuropeptides on digestive enzymes activities and concentration of main hemolymph components, leucokinin II was injected into Agrotis ipsilon (Hufn.) and Helicoverpa armigera (Hbn.)5^th instar larvae at doses of 20, 25, 30 and 40 µl. The neuropeptide leucokinin II reduced the release of digestive enzymes, protease, amylase and trehalase; also, it inhibited the formation of total protein. While it exerted a stimulatory effect by increasing the activity of invertase enzyme and the formation of total carbohydrates and total lipid in both A. ipsilon  and H. armigera larvae.