Abstract: Acute toxicities of chlorpyrifos to 14 different hybrids of silkworm (Bombyx mori) were evaluated in the laboratory using the leaf dipping method. Results showed that the 96hLC50 of chlorpyrifos to Haoyue and 7532 were 18426 and 21452 mg·L-1 respectively. While the 96hLC50 of chlorpyrifos to Chunxiao， Zhelei， 872， Xian 2 and 871 were between 29937-33471 mg·L-1 and to Qiushi， Baiyu， CA， Jingsong， JA， Furong and Xianghui were between 3519-45665 mg·L-1， respectively. It is indicated that the toxicities of chlorpyrifos to different hybrids of silkworm were different， and the two hybrids of silkworm Haoyue and 7532 were most sensitive．

Key words: Bombyx mori, chlorpyrifos, acute toxicity, sensitivity