Abstract: Measurements of activities of glyceraldehyde-phosphate dehydrogenase (GAPDH), glycerol-3-phosphate dehydrogenase (GDH)，lactate dehydrogenase (LDH), 3-hydroxyacyl-CoA dehydrogenase (HOAD) and citrate synthase (CS) in the flight muscle of pupal and adult oriental armyworm, Mythimna separata (Walker), a migratory noctuid showed that most of these enzyme activities were significantly higher in the adults than in the pupal, indicating greater activity related to energy metabolism in adult than in pupal stage. Following eclosion, glycolytic activities was higher than lipid metabolism in the first day of the adult life. From the second to the fifth day of the adult life, carbohydrate and lipid metabolism were equally important since the ratio of GAPDH∶HOAD was 1.0.Lipid metabolism, however, seemed to be superior to carbohydrate metabolism by day seven. High levels of GDH and LDH activities from the first to the seventh day of the adult life suggest that both aerobic and anaerobic metabolism were active in the flight muscle of the adult during this period. And high levels of CS activity in the same tissue and same period provided the energy necessary for powerful flight of the moth. The ratio of GAPDH∶HOAD suggests that not only lipid, but also carbohydrate could be utilized as energy substrates during sustained flight of the moth.

Key words: Mythimna separata, flight muscle, enzyme activity, energy metabolism