CALLED metamorphosis.Metamorphosis is a biological process that involves sudden and abrupt changes in the body structure of the animal by cell growth and DIFFERENTIATION. Metamorphosis is generally OBSERVED in amphibians and insects.Insects are divided into four groups based on their development-Ametabolous development- insects without metamorphosis.Paurometabolous development- insects with gradual metamorphosis.Hemimetabolous development- insects with incomplete metamorphosis.Holometabolous development- insects with complete metamorphosis.Explanation-Metamorphosis in insects initiated internally by hormones.Ecdysone hormone is secreted by the prothoracic gland.Metamorphosis is PROMOTED by ecdysone hormone.Hormones are organic substances.Thyroxine is an iodine-containing amino acid secreted by the thyroid gland.Pherohormone used by most insects to communicate.