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Subclass: Pterygota

A photograph of the bluebottle _Calliphora vicina_.

A bluebottle (Calliphora vicina), the true flies are extremely agile in flight.

The winged insects (Pterygota) go through distinct stages of development before they become adult - egg, larva, pupa, adult. This type of development is called complete metamorphosis.

The eggs of winged insects hatch into larvae, which are unlike the adults and have no wings. They have a hard, non-living outer skeleton, or skin. In order to grow they must feed until they fill this skin and then shed it, to reveal a new skin.

In order to shed their skins, the larvae develop a new skin underneath, and then shed the old skin. They make the old skin split by swallowing air or water to fill their bodies, and the skin then splits to reveal the new, still soft, outer skeleton in its place. Once the new skeleton has hardened, the larvae get rid of the air or water and then they have room to grow into the new skeleton, and the process is repeated. They do this between four and ten times.

This process of shedding the skin is called moulting, or ecdysis. The stages between moults are called instars or stadiums.

Metamorphosis is controlled by three types of hormones, including a neurosecretory hormone. Neurosecretory means it is produced in the insect brain.

The details of the process of metamorphosis allows the winged insects to be classified into two main groups - Exopterygota and Endopterygota.

Related links: Pterygota

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