Globally the crisis of food is a major cause of concern. To increase their yield without interference, indiscriminate and unmanaged application of chemical fertilizers coupled with highly toxic pesticides has resulted in irreversible destruction of soil ecology greatly affecting non-target organisms, especially earthworms and deteriorating soil fertility. Ecotoxicological research has helped us in detecting and understanding the mode of action of a varied spectrum of xenobiotics in agroecosystem. In the present study acute toxicity of four pesticides viz. Pendimethalin, Pretilachlor, Dimethoate and Cypermethrin from different groups was compared on indigenous epigeic earthworm species Perionyx excavatus (Perrier, 1872)[23] and the changes in cocoon production and specific activity of acetylcholinesterase enzyme due to long term exposure of sub-lethal doses of pesticides ie T1 (25% of LC50) and T2 (50% of LC50) values under controlled laboratory conditions. From the experimental results we could observe that all of the pesticides showed a significant amount of reduction in cocoon production in earthworms. Cypermethrin (LC50-0.012 mg/kg) was most toxic to earthworms with no cocoon production in T2 dose, but Pendimethalin showed the maximum suppression in the specific activity of acetylcholinesterase with an enzyme inhibition percentage of 63.2% and 72.4% in T1 and T2 doses respectively than control (N) value.