Control of the developmental timer forDrosophila pupariation

In the insectDrosophila, formation of the puparium marks the onset of metamorphosis and serves as a useful marker for developmental progress. The cells of the adult remain diploid and divide during the larval stage while the larval cells become polytene and do not divide. We use a high dose of gamma-irradiation (10 krad) to selectively delete the imaginal lineage from the developing larvae ofDrosophila melanogaster. We find that animals depleted of imaginal cells including those of the imaginal brain pupariate only if the larval cells are allowed to mature, demonstrating that the larval cells harbor the primary developmental timer for this process. However, proliferating imaginal cells can exert a negative influence on the timing of pupariation.