Study On The Flight Ability And Interaction With Reproduction Of Spodoptera Frugiperda(J E Smith)

The fall armyworm(FAW;Spodoptera frugiperda Smith)(Lepidoptera: Noctuidae)is a major invasive agricultural pest.Originating from the Neotropics,FAW has recently invaded many countries and regions in Africa and Asia.In late 2018,FAW made its arrival in Yunnan province and subsequently invaded most parts of China.It posed a major threat to the production of important crops such as corn and wheat etc.Long-distance migration and strong reproductive ability are the biological basis of rapid population expansion.At present,there are relatively few researches on the flight biology of FAW at home and abroad,and the researches of migratory mechanism and disaster mechanism have rarely been studied in-depth.In view of this,this research empirically assessed its flight activity under varying physiological factors and climatic conditions using a flight mill,and assessed the relationship between its flight and reproduction,in order to further understand its flight potential,and provide theoretical basis for elucidating the migratory mechanism and disaster mechanism.The main results were summarized as follows:(1)1-5 day-old adults had strong flight capacity,with the 3 day-old moths reached the peak and then gradually declined.The average flightdistance,flight duration and flight velocity were(29.21±1.54)km,(11.00±0.47)h and(2.69±0.10)km/h,respectively for 3 day-old adults in a 24-h tethered flight.There was no significant difference in the wingbeat frequency among 1-11 day-old adults,which took a range from 42.39 Hz to 44.64 Hz.Wingbeat frequency of 13 day-old adults was significantly lower than that of 1-9 day olds.There was no significant difference in flight distance and flight duration between male and female moths at the same age.(2)In an empirically assessment of its flight activity under varying climatic conditions using a flight mill,FAW exhibited superior flight performance at 20-25 ? and 60-90% RH.The environment of high temperature,low temperature or low humidity was not conducive to the moths' flight.When quantifying flight performance of FAW over 5consecutive nights(i.e.,10 h/night)under optimum climatic conditions,all flight parameters initially increased and then gradually dropped,and FAW adults attained a total flight distance,duration and velocity equal to(73.05±5.11)km,(24.48±1.17)h and(2.85±0.14)km/h.(3)Flight distance and flight duration of the adults supplied with complemental nutrition were significantly higher than those of adults only supplied with water.The effect of mating on flight ability of FAW is relatively less.There were no significant differences in flight distance,flight duration and flight velocity between mated and unmated moths,only the wingbeat frequency decreased significantly.Oviposition period and fecundity had a significant effect on flight ability of the moths.The moths of laying eggs for 1-3 days or laying 0-1000 eggs had no significant difference compared with the moths without laying eggs.The results showed that flight ability of the moth did not change in the early stage of oviposition,but decreased significantly in the middle and later stages.(4)1–3-day-old adults that had undergone 10-h tethered flights had a significantly shorter pre-oviposition period(POP)and greater oviposition synchronization but did not show any differences in fecundity,oviposition period,mating percentage or other reproductive variables.Further studies on moths after 1.25–15-h tethered flights indicated that the reproductive process of adults could be fully triggered by flight activity longer than 2.5 h.Dissection of the reproductive organs also showed that tethered flight promoted ovarian and testicular development of FAW.This study constituted a first comprehensive assessment of FAW flight performance,and the optimal temperature,humidity and migration age were determined.The results provided a scientific basis for the in-depth analysis of the migration pattern and trajectory of the moth.In addition,this study showed that appropriate flight activities could promote the reproductive processes of FAW,and migratory activities ofthe moth would increase the possibility of its population outbreak.Such will help to clarify the outbreak mechanism and forecast population dynamics of FAW,so as to improve the forecasting level of the moth.