While a lot of people have probably heard about caterpillar Cocoons, they may not know for sure just what these are. Basically, they are nothing more than a protective casing that is around an insect. This is made of either silk or some other similar fibrous material that is then spun around the the insect during their pupal stage, which is the life stage of an insect that is undergoing transformation. While the most common type of Cocoon are those that are found around butterflies or moths, the egg case of a spider is also a type of Cocoon.
Usually an insect will enter into a Cocoon so that they will be protected from a harsh or unfriendly environment. This is why, most of the time insects will spend the wintertime in their Cocoons. So, as the days get shorter and cooler in the fall, these insects will start to spin a silky envelope around themselves. They will then retreat into this Cocoon and spend the winter without the need for food or water.
You may be wondering just how these Cocoons are made. Well, they are actually made of silk. This silk is spun from 2 glands that are located inside of an insect. These glands are filled with a material that is thick and glue-like. An insect will then work in a figure 8 in order to wrap themselves up inside of this silk. This material is pressed out of the insect's 2 slender threads. These threads will then stick together as they emerge and then grow hard when fresh air touches them.
This is a very interesting process because it has oftentimes been said that the most beautiful butterflies have actually emerged from the ugliest Cocoons. For this reason, many people consider the process of the Cocoon to be a miracle of nature itself.