One or more changes in form during the life cycle of an organism, such as an amphibian or insect, in which the juvenile stages differ from the adult. An example is the transition from a tadpole to an adult frog. The term "complete metamorphosis" is applied to insects such as butterflies in which the caterpillar stage is distinct from the adult. "Incomplete metamorphosis" describes the life histories of insects such as locusts in which the young go through a series of larval stages, each of which bears similarities to the adult. Metamorphosis in both insects and amphibians is controlled by hormones, and often involves considerable destruction of larval tissues by enzymes.