Dietary water intake in Eri-silkwormPhilosamia ricini fedad libitum castor leafRicinus communis from hatching to pupation at 26±2°C averaged 16174 mg/insect. As much as 3966 mg of dietary water is lostvia faeces and 65% of the absorbed water is lost through transpiration retaining only 35% in the body. Rates of water intake, absorption, lossvia faeces and transpiration decrease from the Ist instar to Vth instar larvae and are correlated to the increasing body weight and/or age. Water intake inP. Ricini fed permethrin, a pyrethroid insecticide, treated leafR. Communis averaged 8649 mg/insect which is about 50% less than the normal intake. Water utilization in the insecticide fedP. Ricini is considerably less than the normal. It is suggested, the mechanism by which insecticide inhibit the utilization of water could be through, repellency, disruption of feeding physiology and other chronic toxicity possibly related to insecticide action.