Parasitism Selection And Adaptation Of Anastatus Japonicus On Three Host Eggs

Anastatus japonicus Ashmead as the dominant egg parasitoid against the Japanese giant silkworm Caligula japonica Moore can be reared on factitious eggs of Antheraea pernyi,and also parasitize Bombyx mori,which is a polyparasitic insect.Different hosts directly affect the survival and reproduction of parasitoids,but it’s not clear how A.japonicus select and adapt to three host eggs（A.pernyi,B.mori and C.japonica）.In the study,the selection preferences of A.japonicus to host eggs of different silkworm species under the condition of choice and non-choice test,reproductive strategy based on TWO-SEX life table and male fertility were measured.The results will provide great significance for population evolution of A.japonicus and application of biological control.The main results are as follows:1.Parasitism preference of A.japonicus to host eggs of three hostsWhen three host eggs were provided respectively,A.japonicus reared from the same host（A.pernyi or C.japonica egg）parasitized more eggs on B.mori（18.08 and17.39 eggs）and A.pernyi eggs（17.76 and 16.95 eggs）than on C.japonica egg（13.28and 14.40 eggs）.When three host eggs were provided at the same time,there was a significant difference in the number of parasitized eggs by A.japonicus reared from the same host（A.pernyi or C.japonica egg）with parasitizing highest on A.pernyi eggs（12.07 and 10.23 eggs）,following by C.japonica egg（5.40 and 7.61 eggs）,and parasitizing the lowest on B.mori eggs（1.77 and 0.23 eggs）.The number of parasitized eggs of A.japonicus reared from C.japonica egg was higher than that from A.pernyi eggs.Regardless of rearing host species（A.pernyi or C.japonica）,the development duration of progeny was the shortest on C.japonica eggs（24.65 d、24.16 d）,followed by B.mori eggs（26.69、25.55 d）and the longest was on A.pernyi eggs（27.02、25.77d）.All the progeny that emerged from B.mori eggs were male,there was no significant difference in the progeny male ratio between A.pernyi and C.japonica egg.2.The relationship between size of offspring body and host eggs of different silkworm speciesThere were significant differences in length（2.92,1.43,2.27 mm）,width（2.59,1.06,1.54 mm）and thickness（1.03,0.70,1.38 mm）among A.pernyi,B.mori and C.japonica egg.The body length（4.04 mm）,head width（1.01 mm）and hind tibia length（1.03 mm）of female reared from A.pernyi egg was significantly larger than that from C.japonica eggs（3.48,0.89,0.87 mm）.The male reared from A.pernyi egg were the largest,the body length,head width and hind tibia length were 2.53,0.73 and 0.60 mm,respectively,followed by C.japonica egg（2.24,0.66,0.55 mm）,B.mori eggs（1.60,0.49,0.37 mm）.The body length,head width and hind tibia length of female offspring of A.pernyi and C.japonica egg were linearly related to the host length.The body length,head width and hind tibia length of male offspring of three host eggs were also linearly related to the host length.3.Life table parameters of A.japonicus reared on three host eggsOur results showed that the larval development time parasitizing B.mori eggs was longest;The longest female longevity,the longest oviposition days（O_d）and the lowest fecundity were observed on C.japonica eggs,and the highest fecundity（F）（339.17eggs）was observed on A.pernyi eggs.The age-stage survival rate(s_xj)parasitizing C.japonica,A.pernyi and B.mori eggs for 36 days was 86.67%、84.67%、81.33%.The population fecundity（m_x）and population maternity（l_xm_x）of A.japonicus parasitizing different host eggs increased firstly and then decreased gradually with the increase of age.There was a preference for female offspring on A.pernyi and C.japonica eggs in the early oviposition stage,all the offspring on B.mori eggs were male.Moreover,the intrinsic rate of increase（r）and finite rate of increase（λ）were the highest on A.pernyi eggs(0.1479,1.1594d^-1)followed by C.japonica eggs(0.1435,1.1543d^-1)and the lowest on B.mori eggs(0.1411,1.1515d^-1).Net reproduction rate（R₀）ranged from192.23 to 289.43,which was the highest on A.pernyi eggs and the lowest on C.japonica eggs.In conclusion,A.pernyi egg is the most suitable host for A.japonicus.4.Male fertility of A.japonicus reared from three host eggsThere were significant differences in the number of female wasps that were able to be fertilized and the number of female offspring produced between male wasps reared from three host eggs.The male wasps from A.pernyi,B.mori and C.japonica eggs were able to inseminate 12.7,4.6 and 14.1 female wasps in 24 h,respectively.And inseminated females could produce 1565.5,462.3 and1316.4 female offspring,respectively.The female mated with male wasps from A.pernyi,B.mori and C.japonica eggs can produced 214.5,206.6 and 203.2 female progeny at the first time after emergence,respectively.In conclusion,the male bred by A.pernyi eggs have higher fertility.