Abstract
The term imaginal disc is used to describe structures found in the larvae of the Holometabola. Holometabolous insects can be defined as those in which the final larval instar meta- morphoses into a radically different adult during a quiescent pupal stage; they are thought to be a monophyletic group, distinct from the Hemimetabola. During the metamorphosis of Holometabola, the epidermis must form novel structures that were lacking in the larva, and in some cases, replace larval tissues that were lost. The cells that give rise to the new epidermal tissues of the adult imago are often referred to as histoblasts. When histoblasts are organized into mor- phologically distinct clusters, these structures are commonly referred to as imaginal discs or imaginal buds. This article discusses this defi- nition, and briefly reviews some of the experimental studies examining the biology and, especially, the development of imaginal discs.
