Abstract
ML-236B (Compactin), an inhibitor of HMG-CoA reductase activity and thus of juvenile hormone (JH) biosynthesis, was found to have anti-JH action in the cabbage armyworm, Mamestra brassicae. When 50 μg ML-236B was injected twice or three times every 6 or 9 hr respectively beginning 18 hr before head capsule slippage in the penultimate instar, it caused the formation of larval-pupal intermediates. Later application 6 hr after head capsule slippage only inhibited ommochrome synthesis. This latter effect could be prevented by simultaneous application of JH-I. Thus, ML-236B apparently prevents JH biosynthesis for a short period, but is rapidly metabolized so that the effect is reversible.
