Abstract
Total extracellular space values have been determined in the midguts of 2 lepidopteran larvae, Philosamia cynthia and Bombyx mori. The values found are 42% and 45% tissue water respectively. Intracellular concentrations of Na+, Ca++ and Mg++ are very low, while K+ concentration is 197.2 mEq/l cell water in Philosamia and 180.9 mEq/l cell water in Bombyx.