External support

Human have what is termed an endoskeleton, a bony framework internal to the body that is covered in soft tissue. Many creatures however have an exterior skeleton, an exoskeleton. The advantage of an exoskeleton is that this hard shell forms a rigid structure to support the body and also provides protection for the fragile internal organs. Insects, crustaceans, spiders and crabs all have exoskeletons. Interestingly turtles and tortoises have both an exoskeleton (shell) and an endoskeleton.

The downside of having an exoskeleton is that the rigid shell restricts the size of the growing animal. As the animal grows it needs to moult (a process known as ecdysis) out of its old shell and form a new bigger one. After it has left its old shell the creature is soft and pale in colour and very vulnerable to predation. Over the course of hours the creature pumps itself up with air and the new, larger shell hardens. It may take weeks for the new colour to be fixed. The wings appear at the final moult.

This blog site has pictorially documented several moulting animals – cockroaches, mayflies, dragonflies & cicadas. To add to this list are Gumtree Hoppers (Eurymeloides pulchra), pictured below.

Gumtree hoppers are sap-sucking insects found on eucalypt trees in great numbers during summer. They come in a variety of colours and sizes. As part of their life-cycle Gumtree Hopper nymphs or instars go through a number of moulting steps before a fully formed adult finally emerges. In the photo above the pale winged adult (left) can be seen emerging from the old exoskeleton whilst a number of instars look on.

After some time, days or weeks depending on species, the new adult becomes fully coloured  (pictured right). All that is left is an empty shell hanging from the branch (pictured below).