Reproductive Behavior And Capability And It's Variety On Different Environmental And Circadian Conditions Of Beet Webworm, Loxostege Sticticalis (Lepidoptera: Pyralidae)

The beet webworm, Loxostege sticticalis L. (Lepidoptera:Pyralidae) is one of the major serious agricultural pests in northern China. There have been 26 outbreak years since 1949, and resulted in great yield damage and economic loss during the outbreak years. In order to improve the forecasting and controlling technology of beet webworm based on the ecological and physiological factors of population dynamics, this thesis mainly focused on mating and reproductive behavior, the temptation to the synthetic sex pheromone and the effects of temperature, starvation and flight to fecundity of the beet webworm, the major results obtained were as follows:The mating behavior of L. sticticalis moths were studied under the laboratory conditions (22±1℃, RH 70%, and photoperiod L16:D8). The results indicated that both male and female moths began their mating from day-4, and reached mating peak on day-9. The each daily mating occurred at 4-8 hours after lights off and the mating peak occurred at last 2h. Both male and female moths could multiple mate, mating 1-6 times, 2.4 times on average. Twice-mating was the highest proportion of 32.4%, once-mating followed of 29.4%, and then the proportion deceased with the mating times increasing. Mating duration of the moths lasted from 21 to 148 min (n=145), most mating lasted 50-70 min (42.1%, n=145), followed by 30-50 min (36.6%), less than 30 min (2.8%), and 58.7 min on average. Furthermore, mating duration became longer with moth aged(Y=1.2918x+46.676, r=0.22, P=0.008, n=145); Temperature effected the mating behavior significantly. Firstly, mating rate at 22 and 26℃was 96% and 92% respectively, and at 14,18,30,34℃the mating rate was 47.6%,65.2%,68.1% and 31.8%. This results indicated that mating rate obviously decreased when the temperature out of the range of 22 to 26℃. Secondly, temperature effected each-day initial time, peak time of mating and mating duration obviously:when the temperature changed from 14 to 34℃the beginning time delayed 78min on average, the mating peak delayed 93min, and the mating duration decreased from 84.5 min to 34.7 min, which demonstrated that initial time and peak time of mating delayed with the temperature increasing, and mating duration decreased with the temperature increasing. Lastly, temperature effected the daily mating rate, mating times and days significantly. At 22 and 26℃the daily mating rate, mating frequency and mating days were significantly higher than the others. Besides, starvation and flight had no statistical effect on the mating rate, mating frequency.Based on the study of reproduction of adult L. sticticalis moths, the effect of temperature, starvation, adult weight and fight on oviposition and adult longevity had also been researched. L. sticticalis moths laid most of the eggs (40%-70%) in the first 4 days during the oviposition period. Firstly, preoviposition period and oviposition period shortened significantly with the temperature increasing. At 22℃and 26℃, the total fecundity was the most abundant, the oviposition period was the longest, and the oviposition peak was most obvious; each reproductive parameter decreased when the temperature was beyond the range of 22-26℃. The regression analysis told that the adult longevity and temperature correlates significantly negatively (r=-0.99). Secondly, female weigh positively correlated to the fecundity and each day peal fecundity, the correlation coefficient was 0.78 and 0.67. The preoviposition period after 1 day and 3 days starvation was significantly short than the control. And after 5 days starvation the preoviposition period was significantly longer than 1 day and 3 days starvation, but had no statistical difference to the control. However, starvation had no obvious effect on fecundity, peak daily eggs and adult longevity. Thirdly, the preoviposition period of 1-day and 7-day prolonged significantly than the control after 12h-flight, and the 3-day and 5-day had no statistical difference to the control.12h-flight had no statistical effect on the fecundity. For the 1-day flight for 6h the preoviposition period had no statistical difference to the control, whereas, the preoviposition period didn't statistically differ from the control and the 6h-flight after flight for 12h,18h and 24h. Besides, the fecundity of 1-day decreased with the flight strengthened, but the diference was not significant.The sex pheromone gland (PG) of the female adult was observed by using scanning electron microscope, it located at the eighth and ninth abdominal inter-segment and covered with small spines on the surface. The crude extracts of the PG of 1-day and 3-day female had on obvious inducing effect on the male, and calling and orientation rate of male was less than 15% and 10% respectively. Furthermore, we examined the synthetic sex pheromone identified in Canada in lab and field, nither the single nor composited component of the sex pheromone had better inducing activity to the male than the crude PG extracts. And the lure produced by the reported compent was not able to induce the male moth in field.