| Since its invasion into China,Spodoptera frugiperda(J.E.Smith)has attracted wide attention from various fields.Previous studies on migratory behavior of Spodoptera frugiperda were limited to indoor populations,which failed to fit the actual situation.By measuring the flight ability of the field population,this paper explored the related environmental factors that affect the flight ability of the insect,in order to provide more evidence for elucidating the migration strategy of the insect in China,and further provide more detailed indicators for the prediction of the insect in the future.In this paper,we compared the differences in flight ability of the adults of Spodoptera frugiperda in different days,seasons and regions,and identified the factors affecting the flight ability of the populations of Spodoptera frugiperda growing in the field environment during the larval stage.The main conclusions are as follows:1.Effects of age and sex on the flight ability of FAW(1)There was no significant difference in the speed and flight duration between different days of age in the field FAW population,but the difference between flight distances was significant(P < 0.05).This inspired us to pay more attention to the migration of 2-and 3-day-old adults in field monitoring Among them,under the condition of lifting for 12 h,the flight speed at the age of 4 days was the highest,reaching 2.65±0.22 km/h,and the flight duration and flight distance were the longest at the age of 6 days,being 7.96±0.81 h and 22.66±3.08 km,respectively.There was no significant difference between the maximum instantaneous flight velocity of each day of age,and the values of 2 and 3 days of age were similar.The results showed that the first 6 days of the individuals have strong flight potential,part of the 2 or 3 days of the individuals have strong flight ability.(2)There was no significant difference in flight ability between male and female of the same age(P > 0.05),and two-factor ANOVA of age and gender for three flight parameters showed that age and gender had no significant effect on flight ability.there was no significant influence on flight ability under the interaction of age and gender.(P > 0.05).(3)The probability density distribution of flight duration showed that there were two kinds of population differentiation of strong and weak flight ability in the field.Taking the flight duration of 5h as the limit,two types of population could be roughly divided into strong flying and weak flying.Among the total 150 samples,57 samples had flight duration less than 5h,accounting for 38% of the total samples.There were 93 individuals with strong flying ability whose flight duration was longer than 5h,accounting for 62% of the total,and individuals with strong flying ability accounted for a larger proportion in the total sample.2.Difference of flight ability of FAW in different seasonsThe flying ability of the summer population is weaker than that of the spring and autumn population,and the difference may be mainly caused by the different average temperature conditions,as follows:(1)Under 12 h hoisting,the flight velocity of the summer population was significantly different from that of the autumn population(P <0.001),but there was no significant difference with the spring population(P > 0.05).The flight speed of the population in summer was 2.15±0.08 km/h at the lowest level and2.71±0.10 km/h at the highest level in autumn.The flight duration of summer population was significantly different from that of spring population and autumn population(P <0.001).The flight duration of summer population was only 2.10±0.15 h,while the flight duration of spring population was 4.45±0.41 h.The flying distance of summer population was also significantly different from that of spring population and autumn population(P <0.001).The summer population had the shortest flight distance in three seasons,which was only 05.36±0.51 km.(2)The body length of adults in summer population was significantly shorter than that in autumn population(P < 0.001).The body length of the summer population was 15.58±0.09 mm,while that of the autumn population was 15.96±0.07 mm.There was also a statistical difference in pupa weight between the two seasons(P <0.05),the pupa weight of summer population was 0.20± 0.002 g,and that of autumn population was 0.21± 0.002 g.The pupa weight of all individuals in both seasons was between 0.1 g and 0.3 g.(3)The wing length of the summer population was significantly shorter than that of the autumn population(P < 0.001)and the wing flapping frequency was significantly higher than that of the autumn population(P < 0.001).The flapping frequency of summer population was 50.13±0.67 Hz,and that of autumn population was 46.06±0.60 Hz.The wing length of summer individuals was 11.47±0.40 mm,while that of autumn individuals was 14.72±0.68 mm.(4)The frequency distribution of flight distances between the two seasons shows a clear limit of 20 km.In summer,201 individuals(97.1%)flew below 20 km,but there were also 6 individuals(2.9%)with strong flying ability.The overall flight distance of the individuals in autumn was longer than that in summer.96individuals(77.4%)flew less than 20 km,and 28 individuals(22.6%)flew more than20 km.After chi-square(?2= 30.5,df = 1,P < 0.01)showed different season lawn greed the moth is strong,the weak ability to fly there is a significant proportion of individual differences.3.Comparison of flight ability of FAW in different areasThe evolution of population differences in different regions may lead to different flight strategies.In this experiment,it was found that the flight ability of Nanning population was stronger than that of Yuanjiang population,and the average surface temperature was not the only reason for the difference in flight ability,as follows:(1)The flight ability of the population in Nanning is weaker than that in Yuanjiang,and the difference is mainly reflected in the flight duration(P < 0.001).The average flight time of FAW in Nanning area was 6.16±0.60 h,while that in Yuanjiang area was only 2.99±0.26 h.In Nanning,the average flight distance was 16.9±2.13 km,and in Yuanjiang,the average flight distance was 8.93±1.01 km.(2)In 56 samples from Nanning area,48 individuals with weak flight ability(85.7%)had a flight distance of less than 40 km,and 8 individuals with strong flight ability had a flight distance of more than 40 km(14.3%).In the 99 samples from Yuanjiang area,97 individuals with weak flight ability(98%)had a flight distance of less than 40 km,and 2 individuals with strong flight ability had a flight distance of more than 40km(2%).After chi-square(?2= 7.0,df = 1,P < 0.01)showed that the proportion of individuals with strong and weak flying ability was significantly different between the two regions. |
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