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溴虫腈是一种广泛应用并明确对家蚕毒性较小的农用杀虫剂.为了探讨家蚕对溴虫腈的耐受性产生机制,采用室内生物测定方法检测溴虫腈对家蚕耐受性品系QBA和敏感品系p50的2～5龄幼虫的毒性,并同时测定幼虫体内细胞色素P450和b5的含量.结果表明:随着2个家蚕品系幼虫的发育龄期增加,幼虫对溴虫腈的耐受性也增强,并且溴虫腈对同一龄期幼虫的LC50值是耐受性品系QBA高于敏感品系p50;幼虫体内的细胞色素P450和b5含量也是随着幼虫发育龄期增加,但同一龄期耐受性品系QBA幼虫的细胞色素P450含量高于敏感品系p50,而且QBA的幼虫随着发育龄期对溴虫腈的耐受性增强与细胞色素P450含量的增加具有极显著的正相关性(P＜0.01),与细胞色素b5含量的增加则无相关性.初步推测不同家蚕品系对溴虫腈的耐受性与体内细胞色素P450含量可能有一定关联.“,”Chlorfenapyr is a widely used agricultural insecticide,which has low toxicity to silkworm (Bombyx mori).In order to explore the tolerance mechanism of silkworm to chlorfenapyr,in-door biological assays were conducted to determine toxicity of chlorfenapyr to silkworm larvae of the 2nd to the 5th instars from the chlorfenapyr tolerant strain (QBA) and the chlorfenapyr susceptible strain (p50).Meanwhile,the contents of cytochrome P450 and b5 in silkworm larvae were measured.The results showed that tolerant of silkworm larvae to chlorfenapyr increased with development of larvae from the two tested strains.However,the LC50 of chlorfenapyr to silkworm larvae from the tolerant strain QBA was higher than that from the susceptible strain p50 in the same instar.The contents of cytochrome P450 and b5 in silkworm larvae also increased with growth of the larvae,and the content of cytochrome P450 in tolerant strain QBA was higher than that in susceptible strain p50 in the same instar.Moreover,as the larva instar advanced,chlorfenapyr tolerance of larvae from QBA strain had a significantly positive correlation with content of cytochrome P450 (P＜0.01),but had no correlation with content of cytochrome b5.It is speculated that the tolerance of different silkworm strains to chlorfenapyr is related to the content of cytochrome P450 in larval body.