Finally, a view of the little caterpillar that lives within this fascinating construction! The Case moth is said to spend most of its life as a caterpillar. This is the larval stage of the moth that can last up to 2 years in some species. Once the structure is constructed the caterpillars never leave their cases. The moths that emerge from these cases are usually small grey moths with fur on their bodies and clear wings. The females apparently have no wings.