20-Hydroxyecdysone, which is one of the hormone active substances in insects, was found to be contained in an African native plant, and a method of extraction and purification was developed by a chemical company. Then, studies were carried out in order to apply it to sericulture to promote larval maturation. The toxicity of 20-hydroxyecdysone to the 5th instar larvae was low, and experimental results showed that it never affected the survival when orally administered. The administration to newly ecdysed larvae prolonged the larval duration while the administration in the latter half of the 5th instar led to the shortening of the larval duration and growth was synchronized thereafter. The quantitative parameters of the cocoon, especially cocoon shell weight, tended to increase when the substance was administered within 2 days after the 4th ecdysis. The cocoon shell weight tended to decrease when the duration of the 5th instar was shortened by excessive administration of the substance. Thus, it was concluded that 20-hydroxyecdysone was safe and effective for sericulture. Then, the compound was approved by the Japanese Government as an agricultural chemical for use in mounting in sericulture in February 1994.