Heat and CO2rates are measured on M. domesticapupae as a function of age and temperature. Heats of combustion of flies, pupae, and puparia are also measured. Heat and CO2rates decrease for 3 d post-pupation and increase exponentially over 4 d prior to eclosure. Heat and CO2rates are low and increase slowly from 5 to 23C, then rapidly increase from 23 to 26C, then more slowly up to 38C where
pupae are stressed. Respiratory substrate varies with age and temperature, is a mix of lipids and carbohydrates, and has an
average carbon oxidation state of -0.3 at room temperature. Humidity, elevated CO2, or reduced O2did not affect pupal metabolism.