Infection of Diacrisia obliqua larva by Apanteles flavipes resulted in a significant decrease in the lipid and protein content of the host. In about 8 days the parasitoid larvae developing in the host not only utilized these components of the host but also depressed food consumption of the host. Consequently, at the time of emergence of the parasitoid larvae, the host tissue consisted of simply carcass. The parasitoid larvae utilized lipids at the rate of 0.9–10.0 μg/mg/day.