斑痣悬茧蜂对受药寄主幼虫的选择性及其后代表现

为探究受到杀虫剂亚致死影响的寄主幼虫对寄生蜂的寄主选择及其子代蜂的影响,以容性寄生蜂斑痣悬茧蜂Meteorus pulchricornis为研究对象,以氯氰菊酯亚致死浓度处理的甜菜夜蛾Spodoptera exigua4龄幼虫为寄主幼虫,进行非选择性和选择性试验。非选择性试验表明,斑痣悬茧蜂成功寄生（完成化蛹）的概率随受药寄主的体重增大而提高,而且受药寄主有效存活的概率亦随其体重增大而提高;与对照寄主相比,寄生蜂对受药寄主的寄生率降低60.2%、子代蜂发育历期显著延长、子代蜂体型（用后足胫节长度表示）显著增大。与来自对照寄主的子代蜂相比,来自受药寄主的子代蜂的寄生能力（用寄生率表示）未受影响,但其后代的结茧率降低10%、发育历期显著缩短、体型显著增大,说明羽化蜂的发育适合度得到了提高。选择性试验结果得出不一致的结论,根据对寄生蜂攻击次数的分析,未发现其在对照与受药寄主之间存在显著偏好;但根据第2次攻击的寄主识别期变量进行的风险分析,受药寄主被寄生风险显著低于对照寄主（低59.7%）,说明寄生蜂偏好攻击对照寄主幼虫。研究结果说明,斑痣悬茧蜂通过偏好体型较大的寄主幼虫,而减轻了受到杀虫剂亚致死效应的间接不良影响。结果表明该寄生蜂具有鉴别出接受亚致死杀虫剂不久的寄主幼虫的能力。

Host Selection and Progeny Performances of Meteorus pulchricornis (Braconidae, Hymenoptera) Affected by Host Larvae of Spodoptera exigua Treated with Sublethal Pesticides

To study influences of host larvae treated with sublethal pesticides on host selection and progeny performances of koinobiont parasitoids, Meteorus pulchricornis-Spodoptera exigua larvae system was studied in non-choice and choice experiments. The host larvae were treated by Cypermethrine at the sublethal concentration. The results showed that more successful parasitism was accomplished in heavier host larvae treated with the sublethal pesticide, which was attributed to higher probability of survival to pupation in these hosts. Treated hosts were attacked much less than the control as much as 2.5 fold, produced progeny parasitoids with longer development time and larger body size. Compared with those emerged from attacking control host larvae, the progeny parasitoids from treated hosts were not affected in parasitism rate, and produced progeny parasitoids with lower pupation rate, shorter development time and larger body size, which indicated that progeny parasitoids that emerged successfully were improved in fitness parameters. Inconsistent results were obtained from the choice experiment. While control and treated hosts were equally susceptible to parasitism based on selection ratio, the former hosts were more prone to parasitism than the later at the second time of oviposition, based on failure-time analysis on the recognition time to attacks. Our study suggests that M. pulchricornis could be alleviated from indirect impacts of sublethal pesticides on parasitized host larvae through favor for heavier hosts at oviposition, and might be able to discriminate against host larvae that are exposed to parasitism instantly after receiving sublethal pesticides.