Predation,prey Preference And Life Table Of Arma Chinensis(Fallou)on Spodoptera Litura(Fabricius)and Helicoverpa Assulta(guenée)

Spodoptera litura（Fabricius）and Helicoverpa assulta（Guenée）are two kinds of serious agricultural pests in the world.Biological control is playing an increasingly important role in their control.Arma chinensis（Fallou）,belonging to Hemiptera,Pentatomidae,Asopinae,and Arma,is a predatory insect widely distributed in China.Early studies have shown that A.chinensis has good prevention and control ability against S.litura larvae,but there are few reports on its control effects against S.litura eggs,pupa,and adults.Besides,the control effect of A.chinensis on H.assulta is also in the blank stage.In this study,we investigated the predation ability and bias of A.chinensis against S.litura and H.assulta,and established the life table of the experimental population of A.chinensis by feeding on the two pests.The results can provide data for the prevention and control of S.litura and H.assulta by using the natural enemy A.chinensis in tobacco fields.The main research results are as follows:1.The predation ability of adults of A.chinensis to S.litura were identifiedThe temperature of 26±0.5℃,photoperiod is 16L:8D,RH（70±5）%were determined under the condition of the A.chinensisboth male and female adult of the S.litura eggs,larva,pupa,and adults feeding function response.The result shows that both male and female adults had better predation and control effects on different insect states of S.litura.The A.chinensis male and female adults predation different insect states of S.litura’s exhibited HollingⅡfunctional responses.Female adults of A.chinensis had the highest instantaneous attack rate（1.148）on pupae,while male adults had the highest instantaneous attack rate（1.056）on eggs.The maximum daily predation and pest control effects were 117.65 and 124.1 for female adults and 105.26and 111.2 for male adults,respectively.With the increase of the density of S.litura,the predation of A.chinensis gradually stabilized,but its searching effect decreased.2.The predation ability of adults of A.chinensis to H.assulta were identifiedThe temperature of 26±0.5℃,photoperiod is 16L:8D,RH（70±5）%were determined under the condition of the A.chinensisboth male and female adult of the H.assulta eggs,larva,pupa,and adults feeding function response.The result shows that both male and female adults had better predation and control effects on different insect states of H.assulta.The A.chinensis male and female adults predation different insect states of H.assulta’s exhibited HollingⅡfunctional responses.Both Female and male adults of A.chinensis have the highest instantaneous attack rate(（1.58 and1.422 respectively）on H.assulta（pupae）.The maximum daily predation and pest control effects were 147.2 and 152.2 for female adults and 96.15 and 101.9 for male adults,respectively.With the increase of the density of H.assulta,the predation of A.chinensis gradually stabilized,but its searching effect decreased.The interference response model showed that when the density of A.chinensis was constant,the interference effect gradually increased with the increase of the number of A.chinensis.3.Preliminary master the preference of A.chinensis to S.litura and H.assulta larvaeThe selection preference of the 5th instar nymphs and male and female adults of A.chinensis against the 3rd and 5th instar larvae of S.litura and H.assulta larvae were determined.The results showed that Both male and female adults and the 5th instar nymphs of A.chinensis prefer to predation the 3rd or 5th instar larvae of S.litura.For the 3rd instar larvae of S.litura,the selectivity coefficients were0.105±0.015、0.106±0.021、0.112±0.063,respectively.For the 3rd instar larvae of H.assulta,the selectivity coefficients were-0.140±0.015、-0.151±0.034、-0.287±0.110,respectively.And the difference was significant(F>F_0.01（5,59）=12.138,P<0.01).For the 5th instar larvae of S.litura,the selectivity coefficients were 0.171±0.029、0.162±0.033、0.154±0.027,respectively.For the 5th instar larvae of H.assulta,the selectivity coefficients were-0.323±0.087、-0.336±0.114b、-0.278±0.086b,respectively.And the difference was significant(F>F_0.01（5,59）=15.009,P<0.01).The preference of A.chinensis to S.litura and H.assulta larvae would change with the change of prey density.When the H.assulta density was fixed at 10,the increase of S.litura density would induce the conversion of A.chinensis predation preference to the two pests.Specifically,the predation preference to H.assulta decreased gradually,while the predation preference to S.litura increased gradually.When the S.litura density increased to 15,Adults of A.chinensis’s preference for H.assulta changed from positive（0.103±0.151）to negative（-0.059±0.053）,while the preference for S.litura changed from negative（-0.129±0.023）to positive（0.029±0.029）.4.The life table of the experimental population of A.chinensis feeding on S.litura and H.assulta was establishedThe life tables of A.chinensis feeding on two separate pests were measured.The results showed that A.chinensis can achieve normal growth,development,and reproduction by feeding on both prey.The duration of the 2-5th instar nymphs of A.chinensis feeding on S.litura is significantly shorter than that of A.chinensis feeding on H.assulta,while the life span of female adults is significantly longer than that of A.chinensis feeding on H.assulta,which is to say,the larval stage and adult stage of A.chinensis feeding on S.litura is shorter and longer.A.chinensis feeds on S.litura,and its duration of laying eggs is 41.47 days,the total amount of laying eggs per female was 171.52,and the ratio of female to male was 2.17.The net proliferation rate（R₀）was 65.98,the mean generation period（T）was 99.8353,the intrinsic growth rate（r_m）was 0.04196,and the weekly limit growth rate（λ）was 1.0429.These results indicate that the population of A.chinensis feeds on S.litura,in theory,will increase exponentially by 0.04196 in 99.8353 days,and the population rate will increase by 1.04196 times per day.A.chinensis feeds on S.litura,and its duration of laying eggs is 35.79 days,the total amount of laying eggs was138.50,and the ratio of female to male was 1.44.The net proliferation rate（R₀）was72.04,the mean generation period（T）was 96.8044,the intrinsic growth rate（r_m）was0.04418,and the weekly limit growth rate（λ）was 1.0452.These results indicate that the population of A.chinensis feeds on H.assulta,in theory,will increase exponentially by 0.04418,and the population rate will slowly increase by 1.0452times per day in 96.8044 days.