Abstract
Silkworm larvae. Bombyx mori L., 3rd and 4th (Penultimate) instars, were treated with an anti-juvenile hormone, 1-citronellyl-5-phenylimidazole (KK-22) in the artificial diet. Relationships between larval body weights at the end of instar and head capsule width of the next instar were investigated to confirm the presence of threshold size factors for precodicous metamorphosis. The 4th instar larvae with head capsule width wider than 2.9 mm after treatments of KK-22 at the 3rd instar were induced into precocious pupation. The 4th instar larvae applied with KK-22 increased their body weight during the instar, and a precocious pupation was observed in larvae with body weight of 1.6 times that of controls. Both head capsule width and body weight at presumed final instar seemed important factors for precocious metamorphosis.
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