管侧沟茧蜂寄生对粘虫在玉米植株上分布位置选择性的影响

为明确管侧沟茧蜂Microplitis tuberculifer寄生对粘虫Mythimna separata在玉米植株上分布位置的影响及相关机理,采用生物学观察法在温室和实验室内监测了被寄生与未被寄生的粘虫幼虫在玉米活体植株和离体叶片上的分布及管侧沟茧蜂结茧位置的变化。结果表明,被管侧沟茧蜂寄生的粘虫幼虫在玉米叶片背面的平均分布比例为36.29%,显著高于未被寄生粘虫的14.60%;寄生后第8天开始,被寄生粘虫在黄色叶片上的分布比例显著高于未被寄生粘虫;非滞育和滞育条件下,管侧沟茧蜂在玉米植株黄色叶片上的平均结茧数目分别为19.3个和15.3个,显著高于绿叶上的6.5个和4.7个及土面上的0.8个和0.7个,选择性试验发现湿度在结茧位置的选择中发挥着重要作用。研究表明,管侧沟茧蜂可以通过调控寄主粘虫在玉米植株上的分布位置协助其找到合适的结茧位置。

Impact of parasitism by Microplitis tuberculifer on the distribution of Mythimna separata on corn

To detect the impact of parasitism by Microplitis tuberculifer (Wesmael) on the distribution of Mythimna separata (Lepidoptera: Noctuidae) on corn plant and explore the relevant mechanism underlying it, biological investigation was adopted to record the distribution of parasitized and unparasitized M. separata on live corn plants and detached leaves in the green house and laboratory. The preference of cocoon position selected by M. tuberculifer was recorded meanwhile. The results showed that, 36.29% of M. separata larvae parasitized by M. tuberculifer were distributed on the abaxial blade of corn leaves which was notably higher than the 14.6% of unparasitized ones; more and more parasitized M. separata larvae were detected on the yellow leaves of corn plant than the unparasitized ones from the 8th day after parasitized. Under the nondiapause and diapause conditions, the number of M. tuberculifer cocoons pupated on yellow leaves was, respectively, 19.3 and 15.3, which were significantly higher than those on green leaves (6.5 and 4.7) and in soil (0.8 and 0.7). Selection test suggested that humidity was an important factor for the position selection of M. tuberculifer to cocoon. The results indicated that M. tuberculifer could modify host behavior for finding suitable position to habitat and cocoon.