| This impact of flight activity on the energy reserves employed, variation of juvenile hormone titer and enzyme activity of the migratory noctuid pest insects Mythimua separata and the energy reserves employed of the other nctuid pest Spodoptera exigua was studied, the major results are as follows:For adult of the migratory oriental armyworm moth,the flight activity of insect in the different eclosion day-old had various impact on the energetic reserves employed and secretion of the juvenile hormone (JH). Compared with the non-flight control, the flight activity of 1 day-old moth had the biggest effects on those two parameters, and the regeneration of energetic reserves in the flying individuals was significantly higher, the recovery of energetic materials in 3 day-old moth was similar to that of non-flight one, and 5 day-old moth displayed lower energetic reserves.The effects of flight activity of different day-old female on JH biosynthesis were confirmed in radiochemical assay. For 1 day-old female, the rate of JH biosynthesis was significantly higher than that of control after 36 hours flight, increased to 10 times of the control when flying for 60 hours, and peaked when flying for 108 hours. The rates of 3 and 5 day-old females were higher and lower than that of control, respectively, but none of them reached significant level.After flight 12 hours, the degeneration of the flight muscles of the moth varied with different day old. The flight muscles of 1 day-old female moth on day-1 were degenerated prior to that of control after 6 day flight, and there was no difference in flight muscles in 3 or 5 day-old females moth between flight and non-flight ones. Therefore, it could be deduced that the critical period for activation of the corpora allata of the migratory oriental armyworm moth is probably between 1 and 3 day after its emergence.The effects of the flight of female oriental armyworm moth on the activities of energetic metabolic related enzymes in the flight muscles were studied. These measured enzymes were glyceraldehydes-phosphate dehydrogenase (GAPDH), glycerol-3-phosphate dehydrogenase (GDH), lactate dehydrogenase (LDH), and 3-hydroxyacyl-CoA dehydrogenase (HOAD). In the first 5 minutes of the flight of 3 day-old moth, the activities of all the enzymes which are related to carbohydrate and increased rapidly, the lipid metabolism related enzymes were completely activated, and the activities of HOAD were significantly strengthened. But in flight duration from 5th to 60th minutes, the activities of all energy metabolism related enzymes decreased, suggesting that the flight was going to stabilization. High levels of GDH and LDH activities during flight suggested that both aerobic and anaerobic metabolism happened in flight muscle. The ratio of GAPDH: HOAD suggested that not only lipid, but also carbohydrate in the female, could be employed as energy substrates in the process of flight activity.Juvenile hormones (JH) could be effectively separated by reverse phase high performance liquid chromatography (RP-HPLC). The experiment was conducted on JH isolation and measurement in M. separate moth. Two JH homologues (JHI and JHII) were detected in the corpora allata (CA) of both male and female moth, and the main one was JHII. The JH titers in CA of M. separate moth varied with different day-old moth's flight, but generally the flight could stimulate JH secretion in CA. For 1day-old moth, after 12 hours flight then feeding, JH titer reached peak level in first feeding day, decreased slightly, and then increased with the feeding time, showing the stimulation of JH secretion by flight. According to the peak time of both JH homologue titers, the peak level of JHII and JHI appeared in the 4th and 5th feeding day, respectively.Based on the result that flight activity could stimulate the CA activity of lday-old moth, resulting in JH titer increasing significantly, a inference could be obtained that flight behavior in 1 day-old moth could stimulate moth fecundity behavior, but the correlation between JH titer and fecundity...
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