About Lesson
The cocoon
- The cocoon is formed from a secretion from two large silk glands (actually the salivary glands), which extend along the inside of the body and open through a common duct on the lower lip of the mouthparts.
- The larva moves the head from side to side very rapidly (about 65 times per minute) throwing out the secretion of the silk glands in the form of a thread.
- The secretion is a clear viscous fluid, which on exposure to the air gets hardened into the fine silk fiber.
- The filament-forming cocoon is continuous and ranges in length from 700-1100 meters.
- The cocoons from which moths have emerged are called pierced cocoons.
- These are of low value because continuous thread cannot be obtained. Pieces are removed by instruments and spun into a thread.
