Fatty acid synthesis produces long-chain fatty acids that are principal forms of stored energy and essential constituents of cellular membrane lipids. In animals fatty acid synthesis is catalyzed by fatty acid synthase (FAS) from acetyl-coenyzyme A (CoA) and malonyl-CoA. Cerulenin and C75, potent FAS inhibitors, can inhibit feeding in mammals. Using these inhibitors we examined the effect of feeding inhibition during H. zea larval stage. Growth of larvae injected ($30{mu}g/g$ body weight) with C75 or cerulenin was significantly delayed during the first 8 hrs after injection, but recovered to normal levels within 20 hrs. During the first 8 hr period, the amount of consumed diet in the inhibitor treated larvae was significantly less than the control group. The retardation of larval development could be caused from the reduction of food intake after injection of the inhibitor. The result indicates that C75 or cerulenin inhibits fatty acid synthesis, resulting in feeding suppression in the larval moth as demonstrated in vertebrates. Pheromone production was significantly decreased in the isolated pheromone gland of H. zea females treated with FAS inhibitors. Pheromone production was inhibited by blocking fatty acid synthesis, even though PBAN stimulated pheromone biosynthesis. After topical application of $D_3-16:Acid$ to pheromone glands the relative labeled pheromone amount was increased when the gland was incubated with C75. This result indicates that a part of the pheromone amount could be synthesized from 16:Acid directly when fatty acid synthesis was blocked. These results indicate that the inhibitors have a potential possibility to control insect feeding activity and inhibit pheromone biosynthesis in moths.