Cocoon
The cocoon is made of a thread of raw silk from 300 to about 900 meters (1,000 to 3,000 feet) long. The fibers are very fine and lustrous, about 10 micrometers (1/2,500th of an inch) in diameter. About 2,000 to 3,000 cocoons are required to make a pound of silk (0,4kg). At least 70 million pounds of raw silk are produced each year, requiring nearly 10 billion pounds of cocoons.
Read more about this topic: Bombyx Mori