The comparative study of the physiological control of carbohydrate and lipid synthesis, transport and utilization in intact, adult insects (mosquitoes and other vectors and pests) will be continued. The hypothesis that diglyceride is the main transport medium for fat in insects will be tested as follows: the turnover of (labeled) hemolymph diglycerides, obtained from specific relationships, will be expressed as a percentage of the total amount of expired carbon dioxide. By a similar approach, the contribution of trehalose to the respiratory substrate will be measured. The hypotheses will be further tested under conditions known to increase the metabolic rates (temperature increase or flight). The possibility that insects convert protein to trigylcerides during sustained, exhaustive flights will be investigated. The contribution of fat to the maintenance of the trehalose level will be quantitated by feeding insects with labeled fat of constant specific activity and by determining the rate at which the label appears in trehalose. Evidence for a net conversion of fat to carbohydrate through the glyoxylate cycle will be sought. It will be investigated whether dietary fructose enters the glycolytic cycle as fructose-1- or as fructose-6-phosphate. In order to test a possible role for trehalose in glucose transport in mammals, it will be tried to isolate labeled trehalose after injection of labeled glucose from a mammalian kidney, which shows a low trehalase and a high trehalose phosphate synthetase activity.