Understand insect life-cycles

How do common garden insects reproduce? Ben Hoare explains the difference between complete and incomplete metamorphosis.

Shieldbug life-cycle
Illustration by Stuart Jackson Carter


One of the biggest divides among insects is how they develop – and you can see it in even the smallest back yard. There are two main types of insect life-cycle, complete metamorphosis and incomplete metamorphosis, which you can compare first-hand by looking at shieldbugs and ants. 


Incomplete metamorphosis: shieldbugs

You’ll come across shieldbugs on the foliage of trees and bushes – the young (nymphs) lack wings and are a different colour to adults, but when older start to resemble them in shape. Each stage, or instar, is slightly bigger than the one from which it moulted, and this gradual, stepped development is called incomplete metamorphosis.

The process is seen in bugs, crickets, grasshoppers, damselflies and dragonflies. The image below shows a parent bug Elasmucha grisea.

Complete metamorphosis: ants

Examine a garden ant nest (look under rocks or paving slabs) to get a close look at complete metamorphosis. There are always four stages: egg, larva, pupa, adult. You should spot all four stages in the ants’ maze of tunnels.

This process is seen in ants, bees, wasps, beetles, butterflies, moths and flies. The image below shows a black garden ant Lasius niger.





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