中文摘要：

对半闭弯尾姬蜂寄生小菜蛾幼虫的龄期、温度、密度等影响性比的因素进行了研究、结果表明，当半闭弯尾姬蜂寄生小菜蛾2，3龄幼虫时，所得寄生蜂后代雌蜂所占比例小于雄蜂，而寄生4龄幼虫时雌蜂比例高于雄蜂；当温度控制在15～25℃时，该蜂后代雌蜂所占比例较高，温度高于25℃时，雌蜂比例明显降低；将4，6，8对蜂引入养虫笼所得后代寄生蜂的雌蜂比例高，10，12对时雌蜂比例降低，说明养虫笼内寄生蜂的拥挤会导致其后代雌蜂比例下降．

英文摘要：

Studies were conducted on the influencing factors of sex ratio of Diadegma semiclausum Hellén such as instar temperature, and density. The results showed that the Diadegma semiclausum that parasitized in the 2nd or 3rd instar larvae of Plutella xylostella produced more males than females, however, the parasites parasitized in the 4th instar larvae produced more females than males. The percentage of female was higher when the temperature was between 15 ℃ and 25 ℃ , but significantly reduced above when the temperature reached 25 ℃. When we released four, six, or eight pairs of parasites into per rearing cage, more females were produced, but the percentage of female reduced when ten, or twelve pairs of parasites were released. It indicated that the crowds of parasites induced the decrease of the percentage.of the female.