Response of Isolated Pupal Abdomens of Silkworms, Bombyx mori L., to Injected Ponasterone A (Lepidoptera : Bombycidae) : This work was partly supported by a Grant for Scientific Research from the Ministry of Education, Japan.

Molting action of ponasterone A (PN-A), one of phytoecdysones, was studied on the development of isolated pupal abdomens of female silkworms, Bombyx mori, Isolated abdomens of 10- and 20-days old, especially the former, showed high response to injected PN-A, while fresh abdomens isolated immediately after pupation and 30-day old ones were less susceptible to PN-A. Ovarian development, i.e. ovarian weight and number of eggs produced in the isolated abdomens ran parallel to the dosage within the range of 0.5 to 2.5 μg of PN-A, but no differences in the ovarian development were observed for 2.5 to 5.0 μg injections. High doses folloswed the formation of scaleless adult cuticle.