| The camphor sawfly Mesoneura rufonota Rohwer(Hymenoptera: Tenthredinidae)is considered to be one of the most destructive insect pests of camphor tree around southern of China,including Guangdong,Fujian,Zhejiang,Jiangxi,Anhui,Sichuan and other provinces in China.Since the first report on the camphor sawfly in the 1960 s,many researchers have carried out a series of studies on the morphological features,biological characteristics and control measures of this species.This insect has the characteristics of short life span,larger egg production,and higher fertility.Current study has confirmed that the camphor sawfly co-excit of gamogenesis and parthenogenesis in natural conditions,and has the characteristics of diapause in mature larvae.However,the basic biological characteristics such as the developmental threshold temperature and effective accumulated temperature,the parthenogenesis and the diapause of this insect have not been report.In this thesis,the development and diapause of M.rufonota were conducted under constant conditions.The results showed as follows: 1.Influence of temperature on the development and reproduction of the M.rufonotaThe duration of different developmental stages,survival rate and reproduction of M.rufonota reared at different constant temperatures(19,22,25,28 and 30?)were measured and analyzed,the model fitting between the developmental rate and temperature was conducted,and the developmental threshold temperature and effective accumulated temperature were calculated by using the method of least squares.The results showed that: 1)Within the constant temperatures ranging from 19 to 30?,the average duration of various developmental stages of M.rufonota shortened as temperature rose gradually.This insect needed 34.62 d to complete a life cycle at 19?,while needed 18.97 d at 30?.2)The developmental rates in different stages were significantly positively correlate with temperature,and the relationships between developmental rates and temperature all fitted the quadratic regression model.3)The developmental thresholds of egg,larva,pupa,adult and whole generation were 5.26,3.22,7.66,8.24 and 5.11?,respectively,while the effective accumulated temperatures were 65.58,204.15,121.94,65.01 and 460.29 d·?.4)The accumulative survival rates in different stages were decrease and the adult longevity shortened with increasing temperature.The fecundity was the highest at the temperatures ranged from 22 to 25? and the lowest at 30?,indicating that higher or lower temperature inhibits oviposition of M.rufonota.These results indicate that temperature is a key factor affecting the development and reproduction of M.rufonota,and the optimum temperature range for its development and reproduction is from 22 to 25?.The research results of developmental starting temperature and effective accumulated temperature can provide a scientific basis for effective monitoring and integrated prevention and control of the pest.2.Comparison of female reproductive fitness and offspring life history traits between gamogenesis and parthenogenesis in the camphor sawfly,M.rufonotaThe differences in female reproductive fitness of M.rufonota including female adult longevity,fecundity and egg hatching rate and offspring life history traits including the duration of various developmental stages,mortality,sex ratio and fecundity of offspring between parthenogenesis and gamogenesis at the constant temperature of 25? were determined and analyzed.The results showed that: 1)The female adult longevity of M.rufonota was longer for parthenogenesis than for gamogenesis,while the fecundity and egg hatching rate were similar between the two reproduction modes.2)There were no differences in the duration and mortality of various developmental stages and the fecundity of female offspring between parthenogenesis and gamogenesis.However,significant difference was found in the sex ratio of the offspring between parthenogenesis and gamogenesis,being displayed by that parthenogenesis resulted in male-biased sex ratio,while gamogenesis resulted in female-biased sex ratio.Through the analysis of the research results,we found that the parthenogenesis of the camphor sawfly prolongs the longevity of female adult,which has been confirmed as arrhenotoky.These results showed that parthenogenesis of the camphor sawfly not only makes it possible to establish population,but also can provide a large number of males to offset the insufficient male individuals in gamogenesis.3.Effects of different factors on diapause of camphor sawfly,M.rufonota.The diapause of M.rufonota was conducted under constant conditions using photoperiod,temperature,generation and reproductive mode as influencing factors.The results showed that: 1)This species was a typical long-day pest with a critical night length of 10 h 15min.The second instar larva was the most sensitive stage of the photoperiod.2)the proportion of diapause declined with increasing of temperature range from 20°C to 25°C,while arising under 28°C.3)There was distinct difference in terms of diapause between different genetations,showing the diapause rate in first generation under most photoperiod was less than 50%,while higher than 80% in second generation,and even 100% under natural conditions.4)there was no difference in diapause between the offsprings of parthenogenesis and gamogenesis.5)The order of factors influencing diapause of this pest was generation > temperature > photoperiod > reproductive mode,showing generation was the biggest factor,followed by temperature,photoperiod,and reproductive mode. |
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