Metamorphosis

Metamorphosis means "change of form." It’s the way insects grow and mature. Their lives are divided into separate stages for resting, growing and reproducing.

Gradual growth vs. growth in stages

Humans grow gradually. You began life as a baby and grow a little at a time until you’re an adult. While you’re growing, the basic plan of your body doesn’t change. You have the same body your whole life.

Insects grow in stages. The cycle of stages is called metamorphosis. For many insects, the stages are so different from one another that you might not recognize them as the same animal.


Complete metamorphosis

Complete metamorphosis is the way butterflies, bees, flies, beetles and many other insects develop. Complete metamorphosis has four stages: egg, larva, pupa and adult.  

Egg Larva Pupa Adult
Egg Larva Pupa Adult
Every insect begins life as an egg. The egg is the embryo stage. The larva hatches from the egg. The larva is the eating and growing stage. Some insects don’t eat at all after this stage. Larvae don’t look like adults. Caterpillars, grubs and maggots are larvae that grow up to be butterflies, beetles and flies as adults. A larva’s exoskeleton can’t stretch or grow, so the larva sheds its skin, or molts, several times as it grows. When a larva has finished growing, it forms a pupa (plural: pupae). The pupa is the insect’s transforming stage. Outside, the pupa looks as if it’s resting. But inside, the entire body is rearranging. New organs, muscles and body parts develop. When it has finished changing, the pupa molts one last time, emerging as an adult. The adult is the reproductive stage. The adult has all the identifiable insect features: three body sections, six legs, two antennae and usually wings.


Incomplete metamorphosis

Some insects, such as grasshoppers, dragonflies and cockroaches, develop by incomplete metamorphosis. Incomplete metamorphosis has three stages: egg, nymph and adult.  

Egg Nymph Adult
Egg Sac Nymph Bigger Nymph Adult Grashopper
Early, basic development happens in the egg. The nymph is the eating and growing stage. Nymphs often look like smaller versions of adults, without wings. The nymph’s exoskeleton can’t grow or stretch, so the nymph needs to shed its skin, or molt, in order to grow. The periods between molts are called instars. Each instar looks a little more like the adult form. Wing buds form and grow on the nymph’s back. The adult is the reproductive stage. The nymph emerges from its final molt as an adult. In species that have wings, the wings don’t fully appear until this stage. Adults mate, females lay eggs, and the cycle begins again.

 


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