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Animal Life Cycles and Dispersal

Complete Metamorphosis

Insects such as beetles, butterflies, flies and ants have larvae that are simply eating machines. They have a soft flexible body which contains their digestive system. Although their mouthparts may be well developed, their senses are poorly developed. In most cases this type of larva is surrounded by its food or it has food brought to it by adult insects. The larval stage of insects can last from a few weeks to over a year depending upon the species.

Diagram showing complete metamorphosis © Paul Billiet

This simple larva changes dramatically to become an adult which has wings, reproductive organs and sophisticated sense organs. A resting stage is needed between the larva and the adult; it is called a pupa (pl. pupae).

Pupa of the cabbage white butterfly © Paul Billiet

Inside the pupa all the body tissues of the larva are rearranged. This can take from a few days to two or three weeks depending upon the species of insect. Some insects, however, pass through winter as pupae, so this stage in their life cycle can last for several months.

Silk moth cocoons © Shirley Burchill

When metamorphosis is complete and all the tissues have been rearranged the adult will emerge from the pupa. The skin of the pupa splits and the adult pulls itself free. At first the exoskeleton is soft. The wings are inflated with blood to make them expand. The adult insect must rest while its wings dry and the exoskeleton hardens.

This dramatic transformation from larva to pupa and finally to an adult insect is called complete metamorphosis.

The word "pupa" comes from Latin where it means "a doll".

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