The Occurrence of "Extranumerary" Cuticle Deposition in Transplanted Larval Integument of the Sikworm Bombyx mori (Lepidoptera : Bombycidae)

Abstract

The author indicated in previous reports (KATO, 1973, 1975) that in Bombyx mori pieces of larval integument, if transplanted to a pupa, produced two different layers of cuticle in the process of pupal-adult transformation. In the present experiments, attempts were made to examine the occurrence of the extranumerary cuticle deposition in transplants by preparing the larval donor from different stages of development and by using hosts possessing different hormonal conditions. Pieces of integument taken from larvae of an earlie instar (1st, 2nd or 3rd) and transplanted to a pupa deposited two different layers of cuticle at a higher rate than those from larvae of later instars (4th or 5th) before the host pupa ecdysed to na adult. When placed in a penultimate or last-instar larva, integument pieces from earlier instars always deposited only a single layer of cuticle at the time when the host moulted to the next stage. The extranumerary cuticle deposition in transplants took place even when allatectomized or decapitated pupae were employed as the host. Furthermore, this evidence was obseved in both male and female pupae as the host.