Small
insects like caterpillars and worms build their homes out of materials that
their bodies produce. While undergoing metamorphosis, the caterpillar forms
a protective cocoon spun out of silk threads so that it will be protected while
in its vulnerable state. Different species have very different methods and reasons
for building cocoons. some are not only for themselves, but to protect eggs
or larvae while maturing. For example the caddis fly larvae are stored in long
containers underwater which are formed from sticks, leaves and saliva. The cases
are pulled around when the insects move.