A wide array of biological events in the life history of insects are orchestrated by juvenile hormone (JH) and 20-hydroxyecdysone(20E) [1].They control embryonic development,molting,meta-morphosis,and reproduction.Some processes are governed by one of the two hormones while others rely on both.Larval develop-ment and metamorphosis in the tobacco hornworm,Manduca sexta,is a classic example manifesting the coordination of JH and 20E.20E triggers every molt in M.sexta,from larval-larval molt to larval-pupal and pupal-adult molts;the nature of molting is defined by JH [2].High levels of JH in the early larva instars exert the anti-metamorphic function and 20E initiates a molt that leads to another larger larva.Once the hornworm reaches a critical weight (a body size "check-point"),the synthesis of JH is halted.