Animals go through changes at different times in their lives. They may be protected inside an egg or nest when they are tiny, and may make homes for themselves when they have grown up. Animals also need protection when they are in that awkward phase between the two. Some insects make special structures to keep themselves safe when they are vulnerable.
Galls are growths on plants caused by insects such as Gall Wasps. There are lots of different types and each makes its gall in a particular type of plant, and in a certain type of plant tissue.
A female Gall Wasp injects her eggs into a plant with an ‘ovipositor’, which looks like a sharp needle. It’s thought that special chemicals injected by Gall Wasps make the plant grow differently, forming a gall.
The gall is a safe home as well as a source of food for the babies. The galls that form can be strange and beautiful.
Oak trees are a good place to start looking for galls, such as knopper galls, marble galls, artichoke galls, and silk button spangle galls.
Some animals go through ‘metamorphosis’, changing from a baby into an adult that looks very different. While this change is happening, the young animal is vulnerable and needs to stay safe. Some young insects, such as moth caterpillars, build cocoons for extra protection.
Moth cocoons are made of silk. Some caterpillars add other things to their cocoons, such as plant material, or even their own stinging hairs. This adds camouflage adds another layer of safety.
Some caterpillars build their cocoons underground, while others build them amongst the leaves they fed on.
When the caterpillar has finished building, it becomes a pupa. It changes into an adult moth (metamorphosis) then hatches out of its cocoon.
Caterpillars known as silkworms made these cocoons. A caterpillar makes the silk for its cocoon with its salivary glands. It surrounds itself with up to 900 metres of silk thread.