RELATIONSHIPS BETWEEN AN APPLICATION OF KK-42 AND PUPAL DEVELOPMENT IN THE SILKWORM, BOMBYX-MANDARINA

Populations of Chinese origin of the silkworm, Bombyx mandarina, do no t show arrested pupal stage, however populations of Japanese origin un dergo pupal summer diapause. Hormonal control of this pupal summer dia pause in Bombyx mandarina of Japanese origin was investigated using KK -42 treated pupae of Chinese origin. When an imidazole compound (KK42: 1-benzyl-5-[(E) 2, 6-dimethyl-1, 5-heptadienyll imidazole) was inject ed into the newly ecdysed pupae of Chinese populations, the pupal-adul t development was arrested for as long as 40 days. Resumption of pupal -adult development of the KK42 treated pupae was induced by injection of 20-hydroxyecdysone (20-HE). Oxygen consumption of the KK42 treated animals was very low comparing to the control but it increased gradual ly about 35 to 37 days after treatment. Abrupt increase of oxygen cons umption was observed about 12 hr after the application of 20-HE in the KK-42 treated animals. These results strongly indicate that the pupal summer diapause in Japanese populations of Bombyx mandarina is due to the low level of ecdysteroids in their body thus preventing them from proceeding to the pupal-adult development.