THE RELATIONSHIPS BETWEEN PUPAL DEVELOPMENT AND ECDYSTEROID LEVELS INSUMMER DIAPAUSING SILKWORM, BOMBYX-MANDARINA

In the silkworm, Bombyx mandarina, duration of pupal-adult development was mainly divided into three different types among the Japanese popu lation: the first one was 2 weeks duration, the second was about 3 wee ks and in the third type more than 30 to 40 days were necessary for th e adult development, although these were dependent on the rearing seas ons. However, the average number of days required for adult developmen t was 14 in the majority of the Chinese population. In the third type of pupal-adult development of Japanese population, the development of pupal stage was arrested. Oxygen consumption of the animals of which a dult eclosion occurred at 34 days after pupation was very low during t he pupal development. Ovarian development of these animals was also su ppressed considerably. The fluctuation patterns of ecdysteroid titer i n haemolymph of Japanese population were quite different from that of the Chinese population. Ecdysteroid titer was undetectable at 4 to 13 days after pupation in the Japanese population, but the titer increase d by day-15 and reached a maximum level of 4.5 mug at day-20. The rein itiation of ovarian development was coincident to the increase of ecdy steroids in haemolymph of these animals. It was suggested that the del ay of pupal-adult development may be due to the low levels of ecdyster oids in the Japanese population of Bombyx mandarina.