Animals which take on many forms during their life cycles are called what

Animals that on various body forms during their life cycles are called metamorphic animals. Metamorphosis is the biological process in organisms like butterflies, moths and sea crabs where a change in the body shape and metabolism takes place. The butterfly life cycle involves a metamorphosis from caterpillar to pupa to winged-body butterfly. The insects do it when the external skeleton becomes too small for encasing their developing body.