none Metabolism of fifth instar Manduca sexta larvae was significantly altered during parasitization by Cotesia congregata . The in vivo super(13)C natural abundance spectrum and histological examination of the fat body demonstrated significantly reduced fat levels and increased deposition of glycogen in parasitized insects. super(1)H NMR analysis demonstrated that the free amino acid level was reduced in the hemolymph of parasitized larvae, but control and parasitized insects had similar levels of trehalose. ( super(13)C)2-pyruvate injected into the dorsal vessel was incorporated into numerous metabolites including amino acids, Krebs cycle intermediates, trehalose, and fat. In control larvae pyruvate was incorporated primarily into fat following oxidation to CoASAc. General morphology; Biochemistry; Circulatory system; Parasites diseases and disorders; Parasites; Insect parasites; Hosts; Insect hosts; Host parasite relationships Manduca sexta (Sphingidae); Fat body; Metabolic biochemistry; Hymenopteran parasite effects; Haemolymph; Metabolic changes induced by hymenopteran parasites; Hymenopteran parasites; Cotesia congregata; Metabolism of parasitized hosts; NMR study; Reaction of host to parasite; Metabolic changes induced by Cotesia (Hymenoptera) Cotesia congregata (Braconidae); Lepidopteran hosts; Manduca sexta; Metabolism of parasitized hosts; NMR study; Reaction of host to parasite; Metabolic changes in Manduca sexta (Lepidoptera)