Study On The Influence Of Major Meteorological Factors During Adult Migratory Flight On The Occurrence Extent Of First Generation Of Mythimna Separata(Walker)

Mythimna separata（Walker）is an insect belonging to the Lepidoptera Noctuidae family.Adults have migratory habits,larvae are clustered,gluttonous,and occur in a wide range.They can reproduce throughout the year in areas south of 27 °N north latitude.During the adult stage,M.separata need supplementary nutrition to complete migration and reproductive activities,and the quality of supplementary nutrition during the adult stage can also have an impact on the number of larvae that occur.Wang Gaoping（2006）found that in the spring,the milk vetch on the migratory path of the M.separata was rich in nectar,which could provide energy supplement for the migratory adults of the M.separata.The sharp increase in its area was a key factor in the frequent and catastrophic outbreaks of the slime worm in the 1970s.High temperature and dry weather often lead to high sugar content in nectar,while continuous rainfall and humid weather can easily lead to low nectar concentration.Therefore,meteorological factors can have an impact on nectar concentration,and should also indirectly affect the occurrence of M.separata larvae.Therefore,based on indoor experiments,we conducted a combination of data analysis to explore the impact of meteorological factors during the migration period on the occurrence of the first generation of M.separata.In this study,a 2-day-old suspension flight for 9 hours was used to simulate the continuous flight（migration）of adult M.separata.Using 1% and 50% honey solution concentrations to simulate extremely low and extremely high concentrations of nectar in nature,the reproductive parameters of adult M.separata were measured under the following eight treatment combinations: 1% honey solution + tethered flight,1% honey solution+non tethered flight,5% honey solution+tethered flight,5% honey solution + non tethered flight,10% honey solution+tethered flight,10% honey solution + non tethered flight 50% honey solution+tethered flight,50% honey solution + non tethered flight（based on the research of this research group,this article uses 1% and 50% honey solution to simulate extremely low and extremely high concentrations of nectar in nature,respectively）,to explore the impact of extreme concentrations of nectar on the reproduction and lifespan of migratory M.separata.Analyzing the 1960-1979 and 1980-1992 time periods,using partial correlation analysis and linear regression analysis,to explore which meteorological factors（emigration area,transit area,and immigration area）and the area combination of milk vetch can improve the prediction accuracy of the occurrence degree of an overwintering generation of M.separata during the 1960-1979 and 1980-1992 time periods.The main results are as follows:1.The effects of different concentrations of honey solution feeding,tethered flight,and non tethered flight on the reproductive development of adult M.separata related parameters are as follows:（1）Whether in the tethered flight group or non tethered flight group,compared with 5% honey solution feeding treatment,extremely high concentrations（50%）of honey water can significantly prolong the preoviposition period of M.separata adults and reduce their egg laying uniformity;However,there was no significant difference in the prophase and synchronization of egg laying between extremely low concentration nectar treatment and indoor conventional concentration treatment;Compared with adults fed with 5% or 10% honey solution,extreme concentrations（1% or 50%）of honey solution significantly reduced the egg production of female M.separata moths;The hatching rate of adult larvae fed with 5% honey solution was significantly higher than that of other treatments,while the hatching rate of adult larvae fed with 10% honey water was second.Extreme concentrations of nectar can have a significant negative impact on the mating frequency,mating rate,and oviposition duration of the adult worm,with the lowest mating rate（14.29%）and mating frequency（0.58 ± 0.10 times）at 50% concentration;Feeding on extremely high concentrations of nectar can significantly reduce the lifespan of both male and female M.separata,while females feeding on extremely low concentrations of nectar can prolong their lifespan;In the conventional indoor concentration,the longevity of female and male insects fed with 10% concentration of nectar is the longest,while that of female and male insects fed with 5% concentration is relatively short.（2）Compared with non suspended moths,female moths that fly continuously for two days at 1%,5%,and 50% concentrations significantly reduced their egg production;There was no significant difference in egg production at 10% concentration;Hanging only at 1% concentration can significantly improve the prophase and synchronization of egg laying,as well as the lifespan of male and female worms of the M.separata,while hanging at other concentrations can also prolong the prophase and synchronization of egg laying,but it does not have a significant impact;At concentrations of 1%,5%,and 50%,the tethered flight significantly inhibited the mating rate of adult larvae and hatching rate of offspring larvae of the M.separata,while there was no significant difference in the mating rate and hatching rate under 10% treatment;The mating times under 1%,10%,and 50% treatments were significantly lower than the control,and there was no significant difference in mating times under 5% treatments;The lifespan of both males and females after tethered flight at only 1% concentration was significantly higher than non tethered flight,while there was no significant difference in lifespan between males and females after tethered flight at other concentrations.In summary,the migration of 2-day-old M.separata to feed on nectar under extreme environments is not conducive to their reproductive development.2.The impact of meteorological factors on the migration path of overwintering adults in spring and the relationship to the occurrence area of the first generation of sticky worms in wheat fields during the spring migration period:（1）In 1960-1979,partial correlation analysis showed that in addition to the impact of the area of milk vetch on the migration path,the occurrence area of M.separata was related to the temperature of the emigration area,and（R=0.487,P=0.048<0.05）,the temperature of the transit area（R=0.561,P=0.019<0.05）There is a positive correlation between the humidity at the transit area（R=0.516,P=0.028<0.05）and the rainfall at the immigration area（R=0.507,P=0.032<0.05）;The temperature and relative humidity of the migration destination,the temperature and relative humidity of the transfer destination,and the rainfall in the migration destination can also have a significant impact on the occurrence area of the M.separata.Between 1980 and 1992,only the area of milk vetch can be analyzed to have a significant impact on the occurrence area of the first generation of the M.separata,while changes in various meteorological factors on the migration path have no significant impact on the occurrence of the M.separata.（2）Through linear regression analysis,it was found that during the period 1960-1979,we could establish three regression equations to predict the occurrence area of the first generation of M.separata in wheat fields,namely,using the area of milk vetch（y=0.882X-0.550）（R : 0.721）to predict,using the area of milk vetch X₁ and the rainfall of immigration X₂（y=0.928X₁+0.069X₂-1.390）（R: 0.802）to predict the area X₁ of milk vetch and the temperature X₃ of the emigration area（y=0.995X₁+0.040X₃-7.692）（R: 0.824）were used for prediction.The other meteorological factors on the migration path cannot establish a linear regression equation with the occurrence area of the M.separata.From 1980 to 1992,it was found that we can only establish a linear regression equation between the area X of milk vetch and the occurrence area y of M.separata（y=0.591X+0.357）,and at this stage,the main meteorological factors during the spring migration period cannot establish a linear relationship with the occurrence area of the first generation of M.separata in the wheat field.