Abstract：The ecdysone (20-hydroxy ecdysone, 20E) is secreted by prothoracic gland, which regulates the molting in arthropods insecta, crustaceans and other animals. The silkworm is a holometabolous insect known to undergo four developmental stages from egg to adult. The 20E is indispensable in the development of silkworm. In this work, the amounts of 20E in the silkworm’s hemolymph before and after metamorphosis were found to have no significant differences between male and female. However, the 20E content was similar to the expression pattern of BmVg. When 20E was injected to the body cavity or added to the mulberry leaves, the BmVg transcription in the fat body was induced. The treatments also increased the BmVn content and the egg weight. The treatment of 20E induced BmVg expression directly in the fat body in vitro. We conclude that 20E induced BmVg expression to increase BmVn levels in the silkworm eggs, thus to increase the egg weight.
