Metamorphosis in Animals

In short: During metamorphosis a young animal transforms into an adult form with a completely different body plan, such as a caterpillar becoming a butterfly or a tadpole becoming a frog. The larva and the adult often live in very different ways.

In more detail: The transformation is controlled by hormones. In insects, biologists distinguish complete metamorphosis with a pupal stage from incomplete metamorphosis without one.

In detail

• Complete metamorphosis: Butterflies, beetles, flies and bees pass through the stages of egg, larva, pupa and adult insect.
• The pupa: During the seemingly resting pupal stage, the larva’s body is largely rebuilt, and wings, legs and antennae of the finished insect develop from groups of cells set aside in advance.
• Incomplete metamorphosis: Grasshoppers, dragonflies and true bugs have no pupal stage; their young often already resemble the adult and become more similar with each moult.
• Moulting: Because the hard exoskeleton does not grow, insect larvae have to shed it several times in order to get bigger.
• Hormonal control in insects: A moulting hormone triggers each moult, while a juvenile hormone helps decide whether another larval stage or the adult emerges afterwards.
• Frogs and toads: The tadpole lives in water, breathes through gills and has a swimming tail; during the transformation legs and lungs form and the tail is reabsorbed.
• Thyroid hormones: In amphibians, thyroid hormones drive metamorphosis; these are messengers that also influence growth and metabolism in humans (schilddruese-funktion-und-bedeutung).
• The axolotl exception: The Mexican axolotl normally keeps its larval form with external gills throughout its life and still becomes sexually mature.
• The advantage of transformation: Larvae and adults often use different food and habitats, so they hardly compete with each other (amphibien-und-reptilien-ueberblick, insekten-und-bestaeuber).