Combined acute toxicity of chloride Cd, malathion and acetochlor on Eisenia fetida earthworm STUDIES ON PENETRATION OF ~(14)C-MALATHION AND ITS SYNERGISTIC COMBINATIONS IN ASIAN CORN BORER ( Ostrinia furnacalis) 两种亚致死剂量的农药对亚洲玉米螟化学通讯系统的干扰作用