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Insects - Metamorphosis
Incomplete Metamorphosis
About 12% of all insects go through incomplete metamorphosis. Incomplete metamorphosis has 3 stages.
- Egg - A female insect lays eggs. These eggs are often covered by an egg case which protects the eggs and holds them together.
- Nymph - The eggs hatch into nymphs. Nymphs looks like small adults, but usually don't have wings. Insect nymphs eat the same food that the adult insect eats. Nymphs shed or molt their exoskeletons (outer casings made up of a hard substance called chitin) and replace them with larger ones several times as they grow. Most nymphs molt 4-8 times.
- Adult - The insects stop molting when they reach their adult size. By this time, they have also grown wings.
Complete Metamorphosis
About 88% of all insects go through complete metamorphosis. Complete metamorphosis has 4 stages:
- Egg - A female insects lays eggs.
- Larva - Larvae hatch from the eggs. They do not look like adult insects. They usually have a worm-like shape. Caterpillers, maggots, and grubs are all just the larval stages of insects. Larvae molt their skin several times and they grow slightly larger.
- Pupa - Larvae make cocoons around themselves. Larvae don't eat while they're inside their cocoons. Their bodies develop into an adult shape with wings, legs, internal organs, etc. This change takes anywhere from 4 days to many months.
- Adult - Inside the cocoon, the larvae change into adults. After a period of time, the adult breaks out of the cocoon.
Visit the following insect websites. Write down whether each insect undergoes complete or incomplete metamorphosis. Many of these sites may not come right out and state if the insect's metamorphosis is complete or incomplete. You may have to infer that information from the facts that you find.
Author: LINDA MOSBACKER - Email linda.mosbacker@slc.k12.ut.us