Abstract
1. 1. A juvenile hormone analogue, methoprene, applied to the penultimate instar larvae of the silkworm. Bombyx mori did not affect the larval molt to the last instar but caused the last instar larvae to become dauer larvae without metamorphosis. 2. 2. When the dauer larvae were reared on the artificial diet containing 20-hydroxyecdysone (2 ppm), they showed the events for larval-pupal metamorphosis, cocoon spinning and gut purge. 3. 3. Sensitivity to 20-hydroxyecdysone were found between day 6 and day 10 of the last instar, and the effective dosages were in the range of 1.0–20.0 ppm. An administration of 100 ppm 20-hydroxyecdysone induced the head capsule slippage for the supernumerary larval molt after 2 days. 4. 4. The continuous administration of 20-hydroxyecdysone for more than 45 hr induced the spinning and the following pupal molt in about 30% of dauer larvae. 5. 5. The resultant cocoons accounted for a mean weight of 0.83 g and the pupae for 2.7 g in males and 3.3 g in females, being 30–60% heavier than the maximum weight for control individuals. Those pupae became adults after 10 days without 20-hydroxyecdysone treatment, mated and laid eggs.
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