| Lymantria dispar Linnaeus,Lymantria xylina Swinhoe,Lymantria mathura Moore and Lymantria monacha Linnaeus are four important species of international concern in the genus Lymantria.In recent years,L.xylina has been internationally recognized as a potential biological invasion risk due to its similar damage habit to that of L.dispar.However,in southern China,the occurrence and distribution of the four species of the genus Lymantria are not clear,and the understanding of the biological characteristics and dispersal ability of L.xylina is still not comprehensive.In this study,the occurrence and distribution of the four species of the genus Lymantria in southern China were investigated by sex pheromone traps.Meanwhile,the effect of temperature on the growth,development and survival of L.xylina larvae,the reproductive biology of adult L.xylina were studied.To provide a basic basis for clarifying the occurrence and distribution of the four species of the genus Lymantria in southern China,and to deeply understand the dispersal risk of L.xylina,the field light trapping and laboratory phototaxis behavioural response tests of adult L.xylina were carried out,and the flight ability of adult L.xylina was evaluated.The main results are as follows:1.Occurrence and distribution of important species of the genus Lymantria in southern ChinaThe results of continuous investigation by using sex pheromone traps in 14 provinces in southern China from 2007 to 2022 showed that L.dispar,L.xylina,Lymantria dissluta Swinhoe and Lymantria marginata Walker were distributed in southern China,while L.mathura or L.monacha were not found.L.dispar mainly occurred in the southwest region,including Sichuan,Chongqing,Guizhou and Hubei provinces(municipality directly under the central government),with a large quantity in Chengdu of Sichuan Province.L.xylina mainly occurred in the southeast coastal areas,including Fujian,Guangxi and Zhejiang provinces(autonomous region),with a large quantity in Pingtan of Fujian Province.L.dissluta occurred in six provinces(municipality directly under the central government)of Fujian,Guizhou,Jiangxi,Guangdong,Hubei and Chongqing,and L.marginata occurred in seven provinces(autonomous region)of Hubei,Guangxi,Guizhou,Anhui,Guangdong,Fujian and Hunan,both of them were widely distributed but the occurrence population was not large.The longest occurrence period of adult L.dispar and L.xylina were 85 and 57 days,respectively,and the average occurrence period were 48.2 days and 35.3 days,respectively.The occurrence period of adult L.xylina were mostly concentrated in mid-June,while the occurrence period of adult L.dispar showed a trend of delay and extension with the increase of latitude.The emergence of the two moths showed the similar characteristics of rapid occurrence,rapid decline and concentrated emergence period.2.Characteristics of larval development and adult reproduction of L.xylinaL.xylina larvae could not pupate at 15℃ and 30℃.From 20°C to 28°C,the duration of larval development was significantly shortened with the increase of temperature,and it took an average of 87.2 days for L.xylina to complete larval development at 20℃ and only 34.0 days at 28℃.The initial temperature of larvae development was 14.1℃,and the effective accumulated temperature was 501.9degree-days.The emergence,mating and oviposition behavior of adult L.xylina had obvious circadian rhythm.Both male and female moths appeared the emergence peak at the 9th day of pupal stage,and the peak periods of emergence were 13:00～14:00and 17:00～18:00,respectively.Female moths began to summon male moths about 4hours after emergence,and the peak period was 20:00～21:00.Almost all adult moths could copulate on the first day of emergence,and the peak of mating occurred around0:00.Female moths laid eggs mainly concentrated at 12:00～15:00 and 2:00～6:00,laying one egg mass in an average of 5.5 separated intervals times,and mainly laying one egg mass,with an average number of 361.4 eggs per egg mass.The average lifespan of male and female moths was 4.9 days and 4.5 days,respectively.On the basis of clarifying the structure and changes of the internal reproductive system of adult L.xylina,it was found that male moths were sensitive to light resources at the stage of sexual maturity or post-mating,mainly 3-day-old after emergence.A very small number of female moths in the pre-oviposition stage were sensitive to light resources,mainly 1-day-old.3.Light trapping tests and phototaxis behavioural response observation of adult L.xylinaThe adult stage of L.xylina in Pingtan,Fujian Province was from late May to early July,with the peak period from June 4 to June 14.The field light trapping tests showed that the number of female moths trapped by different wavelength light sources was very small,accounting for only 0.3% of the total number of moths trapped.And the insecticidal lamp with 360 nm wavelength light source had the best effect on trapping male moths.The light power(15～35 W),the hanging height(2～3m),the slope position(top or bottom of the mountain)and the light source type(LED or fluorescent)had no significant effect on the trapping effect,and the trapping effect of the sex pheromone trap was significantly weaker than that of the insecticidal lamp.The flapping lamp behavior of male moths had an obvious time rhythm,and most of the male moths were captured during 21:00～3:00 accounting for 93.5% of the total trapping number.The laboratory phototaxis behavioural response tests showed that female L.xylina that were laying eggs had no phototaxis behavioural response,and the proportion of phototaxis behavioural response in pro-oviposition female moths was low,with an average of 14.6% of individuals experiencing phototaxis behavior responses such as wings flapping and displacement,but only 0.6% of individuals flapping lights for a short-distance flight.The proportion of phototaxis behavioural response in male moths was high,with an average of 57.7% of individuals experiencing phototaxis behavior responses such as wings flapping and displacement,and 33.3% of individuals flapping lights behavior.4.Evaluation of flight ability of adult L.xylinaField observation showed that the female L.xylina had long flight preparation time,fast landing and short continuous flight distance.The results of laboratory flight mill tests showed that the female moths prefered to fly in the daytime,mainly short-distance,with the peak flight period at 11:00～15:00,and a small amount of flight activity at 21:00～3:00,after which they no longer flew,while the male moths flew both day and night and over long distances.The flight ability of adult L.xylina was significantly affected by the day-age,gender and flight duration.The flight ability of adult moths was decreased significantly with the increase of the day-age or flight duration.The flight ability of 1-day-old adult moths was the strongest,and the average flight distances of male and female moths were 8.441 km and 3.975 km,respectively.The female moths no long flew at 5-day-old,while male moths had weak flight ability,but still could fly.The flight ability of female moths was almost lost after continuous flight duration for 16 hours,while that of male moths was weakened after continuous flight duration for 32 hours,but still could fly.Therefore,the flight ability of female moths was weaker than that of male moths,and significantly decreased after mating,which may be related to the egg carrying capacity,weight and load ratio of female moths.In summary,after 16 years of continuous monitoring and investigation,no L.dispar,L.mathura or L.monacha had been found in the southeast coastal area of mainland China.Therefore,there was no risk of long-range dispersal of the three species from the southeast coastal area of mainland China with ocean-going freighters.L.xylina was mainly distributed in the southeast coastal area of mainland China,although the occurrence of local areas was large,but the flight ability and phototaxis of the female moths was extremely weak.Consequently,the risk of long-range dispersal with ocean-going freighters through the phototaxis flight and egg-laying behavior of female moths from the southeast coastal area of mainland China was extremely low. |
PDF Full Text Request