Abstract
Cultured integument from diapausing larvae of Chilo suppressalis Walker reproduced larvalpupal ecdysis after two successive treatments with 20-hydroxyecdysone, firstly with 0.1μg/ml for 24hr, and then with 0.1μg/ml for 24 hr. When a juvenile hormone was added to the culture medium at the time of the first ecdysone treatment, the pupal type cuticle formation was inhibited, the extent depending upon its activity. The rate of the pupal type cuticle formation relative to that of the control, when plotted against the concentration of the juvenile hormone, showed a typical dose-response relationship. The median inhibitory concentration of some juvenile hormones was determined as JH II:0.04ng/ml, JH III:1.9ng/ml and methoprene:0.079ng/ml. Cultured integument from the Chilo diapausing larvae was shown to be one of the most sensitive in vitro assay systems for juvenoids.
