During this stage the cuticle draws away from the imaginal cuticle which is forming beneath, ultimately becoming separated as a thin transparent pellicle through which the form of the adult can be seen.
21, d) is revealed, exhibiting the wings and other imaginal structures, which have been developed unseen beneath the cuticle of the larva.
These centres of renovation are called imaginal disks or folds.
I., II., III., vomitories) the imaginal disks are to all the three thoracic segments appearance completely separated from of the larva; I, 2, 3, buds the hypodermis, with which they are, of the legs of the imago; la, however, really organically connected bud of head-lobes; f, of by strings or pedicels.
Was not at first recognized and the true nature of imaginal disks was not at first perceived, even by Weismann, to whom their discovery in Diptera is due.