Abstract: 【Aim】 To clarify the flight capacity and energy utilization mode in adults of the diamondback moth (Plutella xylostella) during flight. 【Methods】 The flight capacities of the unmated female and male adults of P. xylostella at different day-old ages were examined by tethered flight on a computerized flight mill. After the field population was reared for three (F3) and twenty (F20) generations in laboratory, the differences in flight capacity were compared among various populations. The changes in contents of triglyceride and soluble sugar, and the activities of six key enzymes related to energy metabolism, including glyceraldehyde-3-phosphate dehydrogenase (GAPDH), trehalase (TRE), glycerol 3-phosphate dehydrogenase (GPD), lactate dehydrogenase (LDH), 3-hydroxyacyl-CoA dehydrogenase (HOAD) and citrate synthase (CS), in the thorax and abdomen of the unmated 1-day-old adults at 0, 2, 6, 12 and 24 h after tethered flight were assayed by ELISA kit. 【Results】 Based on the accumulative flight duration (AFD), the population of P. xylostella could be divided into three types: short-flight type (AFD≤4.5 h), intermediate-flight type (4.5 h<AFD≤8.5 h) and long-flight type (AFD>8.5 h). No significant differences in tethered flight capacity were observed among the unmated adults of P. xylostella at different day-old and between female and male adults at the same day-old. The accumalative flight duration of the unmated 1-day-old males was significantly lower than that of the 3-6-day-old males. The average flight velocity and accumulative flight distance of the F3 and F20 populations were significantly lower than those of the field population, and the accumalative flight duration and the proportion of long-flight type individuals in F20 decreased significantly as compared to those of the field population. Within the 24-h tethered flight, the triglyceride contents in the thorax and abdomen of the 1-day-old female and male adults gradually increased; the soluble sugar content in the thorax in resting state was lower than that during tethered flight, while that in the abdomen was decreased first and then increased, and reached the lowest value at 6 h after tethered flight. The activities of six key enzymes related to energy metabolisn in the thorax and abdomen of the 1-day-old female and male adults showed similar change trend, gradually increasing with tethered flight duration. Furthermore, the activities of GAPDH, GPD and HOAD were always at high levels, while those of LDH and CS were relatively low. The activity ratio of GAPDH to HOAD was slightly higher than 1.0, and reached the peak at 2 h after tethered flight. 【Conclusion】 P. xylostella adults have strong flight capacity. Their energy utilization mode during flight is a mixed type, whereas the ability to utilize carbohydrates in the initial phase of flight within 2 h is stronger than that to utilize lipids. In the process of flight, both female and male adults are capable of high-speed aerobic metabolism, and also possess a certain capacity for anaerobic metabolism.

Key words: Plutella xylostella, tethered flight, flight capacity, energy metabolism, enzyme activity