*2.1. Test Chemicals, Selection and Dosage of the Insecticides*

The pesticides used for the present study were two widely used organophosphorus insecticides: Phorate and Dimethoate. Commercial grade formulations of insecticides were used because only commercial preparations are used in agriculture. The commercial grade of Phorate was obtained from agro farmers, Court Road, Srinagar manufactured by Sikkim Pesticide Industries. Rogor® (30% dimethoate) was obtained from Big Farmers, Jahangir Chowk near Budshah bridge manufactured by Cheminova, A/S Denmark. Dimethoate is fairly stable than phorate in aqueous solutions (Table 1).

**Table 1.** Phorate and Dimethoate.


On the basis of the literature data (LC50 values for each insecticide), three sublethal concentrations of these insecticides were selected for the experiment, 0.2 mg/L 0.4 mg/L and 0.6 mg/L for Phorate and 0.005 mL/L, 0.01 mL/L, 0.015 mL/L for Dimethoate.
