The citrate level in tissues of Philosamia ricini (Boisduval) falls rapidly during the first 5 days in the pupal stage, then gradually rises during the next 3 days, more or less in a U-shaped pattern. The citrate level gradually declines from the 8th day onward until, at ecdysis on the 20th day, it is at its lowest point in the entire metamorphic period. Marked utilization of citrate occurs during the periods when the insect changes from embryo to larva, from larva to pupa, and from pupa to adult.