In some adult holometabolous insects, specific epithelial tissues form imaginal discs,
small sac-like clusters of cells that form in the larval body. During metamorphosis,
in response to hormones, the discs undergo dramatic changes including cell proliferation
and differentiation. In Bombyx mori insects, the cuticular protein (CP) genes, which
are expressed at prepupal stage in the wing discs, are divided into six groups according
to their developmental expression profile and responsiveness to steroid hormones.
In this article, we discuss the expression of CP genes in the wing disc, and examine
the molecular mechanisms by which metamorphosis and cell transformations are regulated
by hormones in insects.