Relationship between Food Consumption and Molting of the Silkworm, Bombyx mori.

The present study was undertaken to clarify the minimum level of digested protein required to induce larval molting. Newly-ecdysed fourth-instar larvae of Bombyx mori were reared on semi-synthetic diets containing various doses of protein (5 to 20%, dry weight basis), and the coefficient of digestibility as well as the ecdysteroid level of larval hemolymph was determined. According to the decrease in dietary protein, the ecdysteroid level of hemolymph lowered and the minimum dietary level of protein required to induce molting was found to be 7%. The ecdysteroid level of hemolymph increased when the amount of digested protein exceeded 18mg per larva during the 4th instar. When the protein amount exceeded 19mg, the larvae molted. Larvae reared on a 5% protein diet survived more than 20 days and died without molting. With a 5% protein diet, no increase was recognized in the ecdysteroid level of the larval hemolymph. But when the larvae were fed on a commercial diet in place of the P5-diet, the ecdysteroid level increased, and the larvae were able to molt.