Hypermetabolic response, associated with prolongation of the last larval instar, increased consumption, excretion and enormously increased oxygen consumption was induced by juvenoid treatment of the last instar larvae of Dermestes maculatus. Consequence of hypermetabolism on the nutrient content (water, lipids, carbohydrates, proteins) in the body was investigated. Juvenilized larvae differed from controls mainly in their very intensive metabolism, higher water and fat content and lower glycogen content, but no significant difference was found in the protein content. A possible interpretation of the results in comparison with the observations of other authors is presented.