A single Red-back female can produce up to 1000 eggs over her lifetime.

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butterfly, Link to Butterfly life cycle images
Butterfly life cycle

Life Cycles

The life cycle of an insect begins with an egg, which then hatches into a larva. For the juvenile insect, life is taken up with eating, growing, moulting, and growing bigger until it is ready to become an adult.


To grow bigger, an insect needs to shed its tough outer exoskeleton, or moult. When the insect is ready, the old exoskeleton cracks open and the insect slowly crawls out. Free of its old ‘skin’, the insect stretches itself out, puffs itself up and dries out its new exoskeleton.

Juvenile insects moult many times as they grow, often changing into quite different organisms by the adult stage. A change in form is known as metamorphosis. Depending upon the species, an insect’s life stages are characterised by either complete or incomplete metamorphosis.

Complete Metamorphosis

Insects that undergo complete metamorphosis are called holometabolous. They have four life stages: egg, larva, pupa and adult. The larva looks dramatically different to the adult insect, and must go through a pupal stage before it develops into an adult.

Pupation occurs at the final moult. It is an apparent inactive stage during which the larva undergoes dramatic change. When it emerges, the pupa has become an adult. It has wings, fully functional reproductive parts and looks just like its parents.

Complete metamorphosis gives insects a significant survival advantage. The adults and larvae, being different, do not compete for the same food sources and have different predators.

Metamorphosis Diagram - complete

Complete metamorphosis occurs in 85% of known insect species. That includes all of the major successful insect groups such as beetles, wasps, bees, ants, flies, moths and butterflies. Other insect species that undergo complete metamorphosis include fleas, alderflies, lacewings, scorpion-flies and caddisflies.

Incomplete Metamorphosis

Insects that undergo incomplete metamorphosis are called hemimetabolous. They have three life stages: egg, nymph (larva) and adult.

A hemimetabolous insect begins life as a wingless nymph. In many cases it looks like a miniature adult. With each successive moult, the insect increases in size and looks more and more like an adult. On a flying insect, wings will gradually appear. After the last moult the insect is fully adult, able to use its wings and reproduce.

Metamorphosis Diagram - incomplete

Insect species that undergo incomplete metamorphosis include silverfish, mayflies, dragonflies, damselflies, stoneflies, cockroaches, termites, praying mantids, earwigs, grasshoppers, stick-insects, web-spinners, booklice, parasitic lice, true bugs and thrips.

 Earwigs  Alderflies
 Stoneflies  Caddisflies
 Scorpionflies  True Bugs
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Illustration of complete metamorphosis, link to large image
Complete metamorphosis

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Illustration of incomplete metamorphosis, link to large image
Incomplete metamorphosis
© Museum Victoria Australia