Cocoon also means a protective covering of PVC (Poly vinyl chloride, a plastic substance), sprayed over machinery such as large guns, and other military equipment on board ships. The covering provides airtight seal and prevents rust during long periods of storage and transport.
Cocoon of the caterpillar, Manduca Sexta, smells strong tobacco. Predators avoid the unpleasant smell. The tobacco smell is due to tobacco leaf, which is the food of the caterpillar. When the caterpillar hatches from egg, it is blue colored. On eating tobacco leaf, it takes yellow carotenoid molecules.
The yellow substance mixes with the blue blood of caterpillar and turns it green. The caterpillar merges with the background.
Nicotene of tobacco leaf is normally toxic. But the caterpillar separates nicotine and eliminates from its body. When it becomes pupa, the nicotine forms a protective cover.
Metallic blue wasp does not build its own mud cocoon. It uses the abandoned nests of other wasps. It repairs the damaged portions with mud, and lays eggs in the cells of the nest.
Females of the European Bee wolf cultivate bacteria (a streptomyces species, which is an antibiotic) in the glands of their antenna. The bacteria are applied to the eggs. The larvae that hatch out of the eggs take up the bacteria and apply them to the silk threads of their cocoons. The cocoons are protected from fungal infections, by the streptomyces bacteria.
Gauze like cocoons is characteristic of pupa of Diamond black moth. The cocoons are found attached to leaves or stems of cabbage plant. The gauze locks small pockets of air and acts as an air conditioner for the pupa.
Body and skin care parlors advertise Aromatic moor mud cocoons for the tourists. Soft and wet moor mud is applied to the body and is allowed to dry and form a tight cocoon over the skin. It is believed, such a cocoon treatment relieves tiredness as well as muscular aches and pain.
A similar treatment with mineral rich earth of Arizona desert, keeps the skin hydrated, and makes it smooth and shiny. These cocoon treatments are quite expensive and meant for those who are beauty conscious!