Effect Of Different Host Instar,Temperature And Sugar On Development Of Microplitis Similis(Hymenoptera:Braconidae)

This article has observed and described the morphology of each developmental stage of Microplitis similis.The effects of different instar hosts on the development of M.similis were studied.The life table of the parasitoid was established when the Spodoptera litura larvae were used as hosts under different temperature conditions.The lower thermal thresholds and effective accumulative temperature of the parasitoid were calculated.It is beneficial to the assessment of the number generation of parasitoids every year in Changsha.The effects of two different nutrients on the fertility of the parasitoids were measured.In the summer,the parasitoid could efficient control S.litura in the net room.The main results are shown as follows:?1?Photograph and describe the morphology of each developmental stage of M.similis,it provides a theoretical basis for the identification of its morphological characteristics.In no-choice tests,M.similis can parasited 1-3 late instar host larvae and not parasiate 4th and5th,and the parasitization rates were highest in 2-3 early instar larvae.In choice test,M.similis preferred to parasitize 3 early instar host larvae.Each development stage of M.similis and all morphometric features of wasp offspring increased with increasing host instar.Parasitized S.litura larvae showed a pronounced reduction in food consumption and weight gain.?2?The developmental threshold temperature and effective accumulated temperature of M.similis adult were 10.19°C and 223.22 DDs,respectively.According to the law of effective accumulated temperature,it can be deduced that about 13 generations can occur every year in Changsha.In the range of 18 to 33°C,the development period of each stage and the longevity of adult parasitoid were gradually shortened with the increase of temperature.The maximum fecundity of the parasitoids was at 27 and 30°C,45.07 and41.60 parasitoids,respectively,and the minimum fecundity was at 18°C,only 8.37parasitoids.Net reproductive rate?R₀?,the intrinsic rate of increase?r_m?,and the finite rate of increase???of the parasitoids increased with increasing temperature,and the average generation period?T?will decrease with increasing temperature.When the mated female parasitoid was stored with low temperature,there was no significant change in the number of parasitoids from its offspring and the ratio of female parasitoid was significantly decreased.?3?When M.similis uses water,30%sucrose,and 30%dextrose solution as food,Feeding sugar source could significantly increase the survival rate of female parasitoids.In terms of fecundity,Females fed with sugar sources had higher number of cocoons,offspring parasitoid,emeragance rate,females,males and ratio of female than the water treatment group.In the pre-adult of the offspring of the female parasitoids fed with each nutrient,supplementing sucrose can shorten the cocoon period and pre-adult period of its offspring.?4?In the summer,M.similis was able to inhibit the population dynamics and damage of S.litura larvae in the net room in the field.In the first treatment experiment,after the release of parasitoids,there was a certain inhibitory effect on the number and hazards of the first generation S.litura larvae.In the second treatment experiment,after the release of parasitoids,there was a certain inhibitory effect on the number and hazards of the first and second generation S.litura larvae.In the third treatment experiment,after the release of parasitoids,there was a certain inhibitory effect on the number and hazards of the first generation S.litura larvae.