What is metamorphosis?
Many insects, amphibians and invertebrates undergo something called metamorphosis. This means that the animal undergoes major changes in appearance from newborn to adult. Metamorphosis is usually divided into two categories – one called complete metamorphosis and the other called incomplete metamorphosis.
Most amphibians go trough complete metamorphosis, from an egg...
Photo: Geoff-Gallice-CC-BY
...to tadpole...
Photo: Benny-Mazur-CC-BY
...that eventually gets legs, looses its tail and gills...
Photo: Ellika-Nordström-Malmö-Museer
...and grows into an adult frog.
Photo: Ellika-Nordström-Malmö-Museer
The complete metamorphosis in insects starts with an egg...
Photo: Gilles-San-Martin-CC-BY-SA
...that hatch into a caterpillar...
Photo: Superdrac-CC-BY-SA
...that pupates for the last stage of the transformation.
Photo: hamon-jp_CC-BY-SA
The adult insect, called imago, emerges from the pupa. When the wings unfold...
Photo: Entomolo-CC-BY-SA
...the last stage of the complete metamorphosis is finished. The photo shows a common yellow swallowtail.
Photo: Thomas-Bresson-CC-BY
Bees also go through complete metamorphosis. The photo shows eggs and larvae in a bee hive.
Photo: Waugsberg-CC-BY-SA
The different stages in a honey bee pupa.
Photo: Waugsberg-CC-BY-SA
An adult honey bee after the metamorphosis from egg, to larva, to pupa to this stage.
Photo: Richard-Bartz-CC-BY-SA
From egg, to larva, to pupa, to adult
Butterflies, flies, ants, bees and frogs are examples of animals that undergo complete metamorphosis. In insects with complete metamorphosis, the stages are four; from egg, to larva, to pupa and finally adult (also called imago). The stages of frogs are slightly different from those of insects. The larval stage of frogs is called tadpole, and develops into semi-adult frogs rather than pupating. This is true for most of the amphibians.
Dragonfly larvae are called nymphs, and look more like the adult dragonfly than for example a caterpillar resembles its butterfly adult form.
Insted of pupating, the dragonfly nymph molts several times to grow. This photo shows an adult dragonfly emerging from its old skin.
Photo: L.-B.-Tettenborn-CC-BY-SA
Earwigs also go through incomplete metamorphosis. Their larvae, called nymphs, look like tiny versions of adult earwigs.
Photo: Tom-Oates-CC-BY-SA
Incomplete metamorphosis skips pupation
Dragonflies, earwigs and stink bugs are examples of insects that do not pupate, but turn into adults by moulting. They simply skip the third stage altogether. Instead, the larvae look like small versions of the adults, and are called nymphs. Nymphs sometimes shed their skins several times before becoming fully developed and sexually mature.
The axolotl is a salamander that doesn't go through metamorphosis. Other salamander tadpole loose their gills when getting older, but the axolotl looks like a tadpole all its life.
Photo: Johanna-Rylander-Malmö-Museer
An axolotl tadpole with the same gills around its head, as it will keep as an adult.
Photo: Orizatriz-CC-BY-SA
Lake Xochimilco, one of very few places where axolotls live in the wild.
Photo: Juan-Manuel-Gomez-Ruano-CC-BY-SA
The smooth newt goes through complete metamorphosis and looses its gills as an adult.
Photo: gailhampshire-CC-BY
Larva for life
The axolotl belongs to the salamander family. It is highly endangered, and is now found only in a few streams near Mexico City. The axolotl does not undergo metamorphosis like other amphibians, but remains in the larval, juvenile stage throughout its life! Other amphibians lose their gills as they develop from larva to adults, but the axolotl retains its gills and larval appearance for its entire life.