Effect Of Temperature On The Population Dynamics Of Eocanthecona Furcellata(wolff) (hemiptera: Pentatomidae)

Temperature plays an important role in the survival,growth,development and reproduction of the insects,and the fluctuation of temperature has its seasonal regularity.Insects could regulate their population structures according to the seasonal temperature changes during the evolution process.Eocanthecona furcellata（Wolff）（Hemiptera:Pentatomidae）is an important predatory natural enemy of many agricultural and forestry pests.To understand the effect of temperature（especially the low temperatures）on the population dynamics of E.furcellata,the survival and reproduction fitness of E.furcellata were evaluated the method of the experimental population life table at different temperatures,and the predatory efficiency of E.furcellata on Spodoptera litura（Fabricious）larvae was evaluated with the method of the function response.The supercooling point and freezing point of E.furcellata were also measured.In addition,the population dynamics of E.furcellata were investigated in the net house during 2018 to 2019,and the development of ovary of female adults were observed during the winter time.Compared with the the laboratory study results and the net house investigation,the effect of temperature,especially the low temperature,on the population dynamics of E.furcellata was analyzed.The results could be used to explain the ecological mechanism of the seasonal adaption of E.furcellata in theory,and also provide technical support for the storage and proliferation release.The main results are as follows:1.Effects of temperature on the growth,development and reproduction of E.furcellata.There was a significant difference in the developmental time,reproduction and of ovarian development of E.furcellata among the tested temperatures（16,18,20,22 and26℃）.Eggs E.furcellata could not hatch at 16℃,however,they could hatch at 18℃,but the 1^stinstar nymphs could not complete their development and died.Eggs could hatch and grow into adults at 20℃,but the female adults died before laying eggs.Results showed that E.furcellata could not complete its generational development at 16,18 and 20℃,in contrast to that at 22℃and 26℃.The higher developmental rate,net reproductive rate（R₀）,the intrinsic rate of increase（r_m）and the finite rate of increase（λ）were observed at 26℃compared to those at 22℃.The anatomy of reproductive system revealed that the ovarian development of E.furcellata female adults was closely related to the temperature.The ovaries of E.furcellata female adult aged from 10 to 70 days were in grade-Ⅰ（diapause）at 16℃.The proportion of grade-Ⅰovaries in each age group of E.furcellata decreased at18℃,though the descent degree was unconspicuous,at the day of 70,about 75%of grade-Ⅰovaries were observed at the 70^thday.However,the proportion of grade-Ⅰovarian reduced gradually with the increase of temperature,while the proportion of grade-IV ovarian（full of mature eggs grains）increase gradually.The proportion of grade-Ⅰovarian was zero of the 50-day-old E.furcellata female adults at 22℃,and the30-day-old female adults at 26℃.Results indicated that low temperature had a significant effect on the growth,development and reproduction of E.furcellata.2.Effects of temperature on the predatory efficiency of E.furcellata.The temperature also had a significant effect on the predatory efficiency of E.furcellata.The amount of prey(the 3^rdand 5^thinstar larvae of the S.litura)consumed by E.furcellata adults was quite low,at 16℃and 18℃,which indicated that the predatiory activity of E.furcellata was inhibited at low temperatures.However,the amount of prey consumed by E.furcellata increased with the increase of temperature.The a/Th value,one of the important predatory function response parameters increased from 11.74 at 16℃to45.07 at 26℃.In addition,the predatory ability of the female adults of E.furcellata was higher than that of the male adults and the 5^thinstar nymphs.3.Seasonal population dynamics of E.furcellata and the characteristics of ovary development in the net house.According to the population dynamic investigation of E.furcellata during 2018 and2019,E.furcellata could occur 5～7 generations a year in net house in Guangzhou The population of E.furcellata changed.The population peaks showed in April and October,and the population valleys appeared in hot summer（July to September）and cold winter（December and January of the following year）.Only adults of E.furcellata during the population valleys.Faced to the high temperature in summer and cold temperature in winter,E.furcellata probablely diapaused in adults.The development of E.furcellata’ovaries was greatly affected by temperature during winter time.About 75%ovarian were at the grade-Ⅰstage,and the temperature was between 10℃and 20℃at the last two week in January2019.The proportion of grade-Ⅰovarian dropped sharply in February,and the temperature rose to 15～25℃.The grade-Ⅰovarian disappear entirely in March,and the proportion of grade-IV ovarian reached to 80%.4.Supercooling point and freezing point of E.furcellata.Male adults of E.furcellata had the lowest supercooling points（-19.28℃）and freezing points（-11.82℃）compared with the nymphs and female adults.The supercooling and freezing points of female adults were-18.42℃and-11.07℃,respectively.However,the supercooling and freezing point values of the nymphs（the second instar to the fifth instar）were relatively high.Results showed that the male and female adults of E.furcellata could tolerated lower temperature than the nymphs.