| White-backed planthopper (Sogatella furcifera) (WBPH) is one of the most important pest on rice in Asia. Because of their long-distance migration, the WBPH usually take place and make great harm to rice in sudden, it is important to know the quantitative change rule in the field and the behaviors of immigration. In order to explore the WBPH population dynamic in the field, the take-off behaviors, its re-emigration capacity , and the trajectory of immigration and emigration ,we conducted this experiment by fixed field investigation, observation in field and in cage , flight capacity testing in the fight mill in 2001 and 2002, and using the historical data in Wuzhong , Suzhou.The 18-year light-trapped data of WBPH in Wuzhong, Suzhou city were analyzed . It showed that the day of first-trapped of WBPH varied among years, and the day of first-trapped of WBPH was often in the early of June, the day of main immigration peak occurred in the early of July. After 1996, the day of first-trapped was observed earlier. The day of first-trapped was significantly correlated with the day of main immigration peak (r=0.5707), and negative correlated with the numbers of immigration generation (r=-0.638). It also showed that the quantity of WBPH had no time lag of autocorrelation and partial-auto-correlation .The WBPH amount in the field from 1986 to 2002 were also investigated. The first-seen day in the field was often observed at July 1 st 5 days, and WBPH often went through 2 generation, the 3rd or even 4th generation occurred in recent years. The growth pattern of WBPH in the field was 2 kind, Pattern 1: G2>G1,G3G2>G3,or sometimes G3 vanished. These two kinds occurred 52.6%, 47.4% respectively, similar among years. The average of generation growth multiple of WBPH in the latest six years were 68.8, 8.2, 2.4, respectively. The G1/G0 was the most high than others, and the multiple decrease with generations. Compared to the multiple of the brown planthopper, it was different that the first generation growth multiple was more high. To the WBPH on thesensitive rice variety, population developed fast, but the rate changed litter compared with common variety. The number of different immigratory time had different contribution to the WBPH quantity in the field. The number of immigration generation in the field was correlated with the number under light-trapped in June. And the 2nd generation in the field were correlated with the number under light-trapped in August and the quantity of the 1 st generation in the field.The procession of the take-off and its effect factors of WBPH were studied by observation in the field and in caged in 2001 and 2002 , in the paddy field on Wuzhong area, Suzhou city. The observation of the field suggested that WBPH immigrated in Suzhou before middle July, and reproduced two generation in this area. From the end of August , there were a few adults beginning to emigrate and in the middle of September, the emigration peak occurred. But the emigration peak occurred in August in the cage. The preparing time of take-off was short and the efficiency was high. And the take-off time was at crepuscular hours in the dawn. When the population density was large, the take-off time would last 10 minutes after sunset, and in the late September, the take-off time would be ahead of normal time, but the finish time would not be ahead if the number of WBPH in the field was large. The observation of cage showed that the emigration ratio per day was about 80 percentage during emigration peak, and in the field , the ratio of take-off was about 50% to 65%. And one-day-old adult also could emigrate in the cage. Wind and rain had obvious effect on migratory take-off behavior. There was no WBPH take-off under the weather of the rainy day and strong wind, the gentle breeze had no effect to the take-off but strong wind could prevent the take-off.The trajectory analysis was conducted in the three altitude of 500m, 1000m and 1500m by the HYSPLIT, it showed that in Wuzhong area, the WBPH on light-tra...
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