The selective toxicity of 10 Bt spore-crystal proteins to Ovomermis sinensis was studied. The results indicated that 7 of them contained both CrylAc and Cry5 proteins (S1-1, S1-4, S3-2, S3-3, S7-1 S7-6 and S8-1 ) , and others only contained CrylAc proteins (S1-8, S2-1 and HD-1 ). We demonstrated that the Bt crystal protein Cry5 from 7 Bt strains were lethal to eggs of O. sinensis. The most effective strain S1-4's LD50 values were 0. 1503, 0. 1313 and 0. 0182 μg total protein/mL respectively at 24, 48 and 72 h. Infective and post-parasitic...