An adult butterfly is the fourth and final stage of the butterfly life-cycle. Butterflies are an essential part of the ecosystem as pollinators and in each of their four life-cycle stages as components of the food chain for other wildlife.
The duration of each stage of the life-cycle may be affected by climate – as a general rule, the cooler the temperature the longer each stage will last.
The four stages to a butterfly or moth life-cycle are egg, caterpillar (or larva), chrysalis (or pupa) and the adult butterfly or moth.
Stage 1 - the egg
This may last from about 3 to 14 days.
The egg will usually be laid on or very near the caterpillar's preferred food plant. Some species deposit their eggs in clusters and some lay them singly; some on the upper surface of the leaf and some on the underside; others prefer to deposit their eggs on flowers, branches or stems of the food plant. And some of the Browns drop their eggs as they perch, fly or walk over the ground.
Caper White laying eggs in clusters (Sydney)
A single Tailed Emperor egg (Queensland)
Stage 2 - the larva (caterpillar)
Generally, this stage may last anything from a minimum of 3-4 weeks to about 9 months. It differs from species to species, and often depending on climate.
The caterpillar stage is the growing stage and to achieve growth the caterpillar needs to eat. Each caterpillar has its preferred food plant/s and will only feed successfully and survive on them. Attempts to eat non food plant leaves will eventually result in the death of the caterpillar.
Caterpillars have a fixed-sized skin for each stage (known as an instar) of their development. Unlike human skin, a caterpillar's skin does not enlarge as it grows. Therefore caterpillars have to periodically shed their skin to gain a newer larger one. This normally happens four or five times during their development. At the beginning of each instar the skin is loose, tightening gradually as the caterpillar feeds and grows, until it becomes tight again having reached maximum size for that instar.
When its skin becomes very tight the caterpillar spins a platform of web on a leaf or a branch and then sits completely still on that web platform for 2-3 days whilst its new skin forms beneath its current one. When the new skin is fully formed the caterpillar changes instar's by breaking out of its old skin and emerging in the new instar displaying its new larger skin. It will now also have a larger head and often brighter colours displayed on its new skin. The new skin needs to dry and harden before the caterpillar will move and resume feeding. They will often recommence feeding by first eating the skin they have just shed.
It is important not to move or touch the caterpillar whilst it is sitting motionless on the web platform growing a new skin. Its firm grip of the web with its old claspers is critical to ensuring it is able to break out of its old skin once its new skin is fully formed - it needs to apply pressure on the old skin around its head area. If you carefully observe the caterpillar over this period you will notice its new head gradually forming below its old one which is at the same time being slowly dislodged. The old head will drop off as part of the actual moulting process when the caterpillar walks out of its previous skin commencing the new instar.
At the end of the final instar the caterpillar will change into a chrysalis.
Early instar Orchard Swallowtail caterpillar on Mexican Orange (Choisya ternata)
Late instar Orchard Swallowtail caterpillar. Note the colour change
Stage 3 - the chrysalis (pupa)
Chrysalises come in a variety of shapes and sizes and are formed in different ways for different species.
The caterpillar of the chrysalis on the left (below) had first spun a girdle of web around its middle and then fixed its hind end to the leaf with more web, so as to support its later change into a chrysalis.
In other species the chrysalis may be attached by a fine silk thread (cremaster) which enables it to hang down, as in the photo below right. A few species pupate on the ground in a protected position in the leaf litter.
It usually takes from about 10 days to more than 9 months for the butterfly to emerge from its chrysalis, depending on the species.
Orchard Swallowtail chrysalis supported by a girdle
Australian Admiral chrysalis hanging by a web (cremaster)
Dingy Swallowtail chrysalis hanging in a girdle
Common Jezebel chrysalis also in a girdle
Stage 4 - the butterfly (adult)
Depending on the species butterflies can live from about 2 weeks to as much as 9 months or maybe even more.
As with all creatures, a butterfly's driving instinct is to reproduce the species.
Male butterflies: Often they will emerge before females; the male's purpose in life is to fertilize females.
Female butterflies: Their purpose is to lay fertilised eggs on or near their foodplant so the next generation of caterpillars can hatch and develop into adult insects.
Both male and female butterflies need to feed to sustain their strength - the male to search for a mate and the female to deposit her fertile eggs. Unlike their caterpillars they do not eat leaves but feed on nectar, or moisture or rotting fruit.
Newly emerged female Orchard Swallowtail
Newly emerged Common Crow waiting for its wings to dry
Compare this old worn Common Jezebel to the one on the right. It has lost most of the scales on its wings.
Main predators and defences
A newly hatched Common Jezebel. How long will it live?
A Small Green-banded Blue that has probably been attacked
by a bird but is still able to fly