Types of Metamorphosis

A. Ametabolous / No metamorphosis:

• The metamorphosis in which there is a gradual increase in the size of the young until the adult dimension is maintained is called Ametabolous.
• Usually, there is no difference between young and adults except the size.
• Eg: Silverfish, sprint tails, etc.

B. Gradual metamorphosis ( Paurometabolous ):

• The life cycle of insects with gradual metamorphosis has three life stages: egg, nymph, and adult.
• Nymphs resemble the adult except that their body parts are out of proportion with each other, and they do not have fully developed wings and external genitalia.
• With each molt, the nymphs gradually develop wings and take on the body proportions of an adult.
• Nymphs have the same type of mouthparts as the adult, and they both feed on the same kind of food.
• Eg: Aphids, grasshoppers, termites, etc.

C. Hemimetabolous / Incomplete metamorphosis:

• The metamorphosis which consists of three stages i.e. egg, naiads, and adult is called hemimetabolous.
• However, the adult insect with incomplete metamorphosis lays its eggs in or near water and the naiads develop in water.
• The adults are flying insects that live out of water.
• Naiads and adults therefore do not eat the same kind of food. Naiads have chewing mouthparts, but the adults have differently shaped chewing mouthparts or no functional mouthparts.
• The naiad and the adult usually differ a lot in appearance although the naiads gradually develop wings.
• Dragonflies, Mayflies, Stoneflies

D. Holometabolous / Complete Metamorphosis:

• The Metamorphosis which consists of four distinct stages i.e. egg, larva, Pup,  and adult is called Holometabolous.
• The larval stages do not look like the adult at all, and they are often worm-like.
• Larvae often have different mouthparts and food habits than the adult, and they often live in places different from the adult.
• Larvae molt several times and get a little larger with each molt, but there is no gradual development of wings or other adult characteristics.
• When a fully grown larva molts, it changes into a pupa.
• The pupa usually does not eat or move around much, but a lot of internal changes take place.
• When the pupa has made all its internal changes, its skin splits and the fully formed adult emerges.
• Most insects with complete metamorphosis are winged in the adult stage.
• The adults do not molt or grow anymore.
• Little flies or beetles, for instance, do not grow to become larger. Flies (Diptera), beetles (Coleoptera), wasps (Hymenoptera), and butterflies (Lepidoptera), have holometabolic life cycles.