Changes of the energy content of different developmental stages in the wax moth Galleria mellonella were investigated by means of combustion calorimetry. The energy content (Q) is highest in L-7-larvae (2.94 kJ per individual), the last stage in Galleria ontogenesis which takes up food, and the specific energy content (q) is highest in adults (37.5 +/- 2.4 kJ g(-1)) with fat as energy reserve. Galleria takes up no further food after pupation and in adult life. The energy reserve for metamorphosis and adult life can be calculated to 1.65 kJ per moth. Heat production rates of wax moths from L-7-instars until death of the adult were recorded continuously by means of longtime calorimetric experiments. Different develomental phases could be clearly distinguished in the calorimetric curves because larval instars, prepupae, pupal instars and adults each showed a specific pattern of heat production. Developmental events such as moultings could be observed with own characteristic patterns of heat production rates. Mean specific heat production rates ranged from 13.7 +/- 3.3 mW g(-1) during cocooning of the L-7-instar, to 5.1 +/- 1.3 mW g(-1) (n = 6) in prepupae. Adults showed a circadian pattern of heat production with resting metabolic rates of 5.6 +/- 2.3 and 10.4 +/- 2.1 mW g(-1) (n = 6) during periods of activity.