草地螟阿格姬蜂的滞育诱导和滞育茧的低温贮藏

Diapause induction and cold storage of diapause cocoons in Agrypon flexorium (Hymenoptera:Ichneumonidae)

为了阐明环境因子对草地螟阿格姬蜂Agrypon flexorium（Thunberg）滞育诱导作用，测定了5个光周期和4个温度处理对阿格姬蜂的滞育诱导和该蜂感受光周期的敏感虫态以及不同时间段低温贮藏对滞育虫茧的影响。结果表明：在17～23％、光照时间10～14h范围内，随着温度的降低和光照时间的缩短，滞育率明显提高。高温能抵消短光照对滞育诱导的影响，在26％下，短光照不能诱导滞育。因此，低温和短光照是诱导草地螟阿格姬蜂滞育的主要因子。草地螟阿格姬蜂感受滞育信号的敏感虫态为卵和1龄幼虫。卵和1龄幼虫感受滞育信号以后，需要在滞育环境中发育到老熟幼虫才能全部进入滞育。将室内诱导的滞育茧在4℃左右环境条件下冷藏80d，成蜂的利化率和寄生能力与没有冷藏的非滞育茧差异不显著，冷藏120d，滞育茧仍有71．7％可以正常羽化。结果说明，町在17℃，光周期8L：16D条件下对寄生后3d内的草地螟Loxostege sticticalis幼虫进行滞育诱导，滞育后的虫茧最佳贮藏时问为80d，不宜超过120d。本研究为室内扩繁、防止蜂源退化、控制寄生蜂发育时间以便适时释放提供了参考依据。

To understand the effects of temperatures and photoperiods on diapause induction of Agrypon flexorium （Thunberg） , the process of induction, the sensitive stage that was susceptible to photoperiod and the effect of low temperature on the storage was investigated. The results showed that when the temperature was between 17 - 23℃ and day length was 10 - 14 h, the diapause rate significantly increased with the decrease of temperature and day length. High temperature counteracted the effect of short day length. When the temperature was 26℃, photoperiod had no effect on diapause. Thus, lower temperature and shorter day length were the major factors that induced diapause of the parasitoid. The parasitoid accepted the signal for diapause at the egg and 1 st instar larval stages. The pre-pupae entered diapause only if the eggs and 1 st instar larvae had been reared in the temperature and the photoperiod for diapause induction till they matured. The emergence rate and the parasitic ability showed no significant difference between adults emerged from the diapause cocoons stored in the temperature of 4℃ for 80 d and those from the non-diapause cocoons without cold storage. After cold storage for 120 d, the emergence rate of the diapause cocoons still reached 71.7%. The results suggested that the photoperiod of 8L： 16D at 17℃ had diapause induction effect on parasitized host larva. The optimal storage time of diapause cocoons is 80 d and should not be more than 120 d. The study provided some reference information for indoor propagation, preventing wasp degeneration and field releasing.