Abstract
1. Samples of all stages of Phyllopertha horticola L. have been analysed for fat, total nitrogen and glycogen. 2. Total nitrogen increases throughout the larval feeding period, while fat and glycogen are laid down mainly in the latter half. 3. From November, when the third-instar larva goes into hibernation, until June, when the eggs have been matured and laid, no food is taken. 4. Of the store of fat and glycogen in the hibernating larva at the beginning of the winter, half is used up by the time the adult emerges. The other half is used in the formation of eggs. 5. Adult feeding provides energy for the post-oviposition activity period.