Ecdysone and Ecdysone-Analogues: Their Assay and Action on Diapausing Pupae of the Cynthia Silkworm

Six ecdysones of plant origin are compared with synthetic α-ecdysone in terms of their ability to provoke normal or abnormal development of diapausing pupae and isolated pupal abdomens of the cynthia silkworm (Samia cynthia). 2. The activity of the seven materials ranks in the following order: cyasterone > ponasterone B > ponasterone A > ponasterone C > α-ecdysone > β-ecdysone > inokosterone. 3. All seven materials provoked normal adult development when injected in critical doses ranging from 0.2 µg. (cyasterone) to 10 µg. (inokosterone). 4. All materials except µ-ecdysone caused extremely abnormal development when excessive doses were administered to pupae or isolated pupal abdomens. The typical result was the formation of naked or nearly naked non-viable moths which failed to complete adult development. 5. Abnormal development is correlated with a telescoping of the early events in adult differentiation, followed by the precocious deposition of new cuticle. 6. Sensitivity to excessive ecdysone or to juvenile hormone disappears simultaneously at about the 60th hour after the initiation of development. 7. The evidence suggests that excessive ecdysone interferes with the cytological expression and implementation of genetic instructions for forming a normal moth. This mode of action is compared to that of juvenile hormone.