Metamorphosis is a process some animals go through to become adults. It is a series of physical changes. Metamorphosis is especially common in insects. Genes and chemicals called hormones control the process.

Many insects go through four stages of metamorphosis: egg, larva, pupa, and adult. An insect hatches from an egg into a wormlike larva. Caterpillars and maggots…

Monarch Caterpillar— First Instar.
This tiny (4 mm long) eating machine has very recently hatched. Its first meal was to nibble at the shell of its egg and now it is tackling the leaf of a Swan Plant. It is still too small to penetrate through the leaf but within a day it will start leaving tell-tale gaps in the milkweed's leaves.
When a caterpillar outgrows its skin it moults, or sloughs off, its old skin. The stage between moults is an instar. Monarch caterpillars have five instars.

Monarch Caterpillar— Second Instar.
The caterpillar is now three days old and 11 mm long.

This Monarch caterpillar, now into its fifth instar and about 50 mm long, has just shed its skin. The skin, which can be seen lying on the leaf behind it, is usually eaten by the caterpillar shortly after moulting. This caterpillar's next moult will result in a chrysalis.

Monarch caterpillar on a Swan Plant milkweed, fifth instar, about 55 mm long and close to pupation. It is now about three weeks old. however this time-span depends very much on temperature and can vary considerably. When they are ready to pupate the caterpillars tend to wander around, sometimes relatively far afield, presumably in search of a suitable chrysalis-friendly site.

By wriggling, as well as rhythmically contracting and expanding, the Monarch larva (caterpillar) pushes its skin upwards. The jade green pupa (chrysalis), at this stage still very soft, can now clearly be seen.

The pupa now starts wriggling and gyrating energetically to finally dislodge its skin. This Monarch took 12 minutes to complete the moulting process.

This beautiful new jade-coloured Monarch pupa is still soft and wrinkled. Some areas of the adult butterfly-to-be are already apparent. Within the next 1 to 2 hours its casing will harden, smooth out and assume the familiar shape of a mature chrysalis.

Shortly before the butterfly is due to emerge the Monarch chrysalis darkens significantly and the orange colour of the wings can be clearly seen through its casing.

Seven minutes have elapsed since this adult Monarch butterfly emerged from its chrysalis. The butterfly's wings have expanded but have yet to harden properly.

A newly emerged adult Monarch butterfly, its wings fully expanded and by now probably fully hardened and functional, slowly makes its way upwards towards a high point on the Swan Plant milkweed.

About two hours after emerging from its chrysalis this beautiful adult Monarch spreads its wings in preparation for its first flight.

The butterfly in this photo is a male. Males have a clearly visible black spot on each hind wing from which pheromones are released.
The next image in this series, also of a recently emerged adult Monarch, is a comparative photo of a female.

Freshly emerged from her chrysalis this female Monarch will soon make her first flight.

The webbing on a female's wings is thicker than the webbing on a male's wings and females do not have the black spots on the hind wings that are a characteristic of males