草地螟发育阶段对伞裙追寄蝇的寄生效果

伞裙追寄蝇是草地螟、黏虫等重大农业害虫的优势寄生性天敌，对害虫种群数量的调控起着不可忽视的作用。本文研究了不同龄期草地螟对伞裙追寄蝇寄生效果的影响，为伞裙追寄蝇的室内扩繁和田间应用提供依据。在温度（25±1）℃，相对湿度（65±5）%，光周期14L：10D实验室条件下研究了伞裙追寄蝇对草地螟2、3、4、5龄幼虫及5龄期不同日龄幼虫的寄生效果，5龄期不同日龄幼虫对寄蝇的发育适合度。结果表明：伞裙追寄蝇对2～5龄草地螟幼虫都有寄生行为，但对5龄草地螟幼虫的寄生率（68.89%）显著高于其他龄期；且寄生5龄幼虫的羽化率最高（73.88%）。伞裙追寄蝇寄生能力随寄主日龄呈现先升高而后下降趋势，其中5龄后2～3日龄寄生率（74.44%）、羽化率（78.76%）均最高，子代发育历期最短，产卵量最高，为最适寄生阶段，说明室内扩繁伞裙追寄蝇寄主选择以5龄期2～3日龄草地螟幼虫为宜。

Effects of Larval Developmental Stage in Loxostege sticticalis on the Parasitismby Exorista civilis

Exorista civilis is an important natural enemy and plays an important role in the biological control of Loxostege sticticalis, Mythimna seperata and other pests. Larvae of L. sticticalis were parasitized at different stadium by E. civilis to evaluate the parasitism rates for the purpose of improving indoor propagation and field application of the parasitoid flies. Under (25±1) ℃, relative humidity (65±5)% and photoperiod 14L:10D, E. civilis parasitized the 2^nd—5^th instars of L. sticticalis, but showed a significantly higher parasitism rate (68.89%) on the 5^th instar than on the other instars, and the highest emergence rate (73.88%) from the 5^th instar host. With the age increase of the host, the parasitism ability of E. civilis increased first and then decreased, the highest parasitism rate (74.44%) and emergence rate (78.76%) was observed from the host larvae at 2—3 days after the 4^th molt. From these host larvae, offspring wasps developed the fastest and realized the highest oviposition. Therefore, it is preferable to select the host larvae at 2—3 days after the 4^th molt as the host in propagation of the parasitoid.