What is "imaginal disks"

Imaginal \Im*ag"i*nal\, a. [L. imaginalis.]

1. Characterized by imagination; imaginative; also, given to the use or rhetorical figures or imagins.

2. (Zo["o]l.) Of or pertaining to an imago.

   Imaginal disks (Zo["o]l.), masses of hypodermic cells, carried by the larv[ae] of some insects after leaving the egg, from which masses the wings and legs of the adult are subsequently formed.