Cocoon (silk) in the context of "Sangju"

Silk is a natural protein fiber, some forms of which can be woven into textiles. The protein fiber of silk is composed mainly of fibroin. It is most commonly produced by certain insect larvae to form cocoons. The best-known silk is obtained from the cocoons of the larvae of the mulberry silkworm Bombyx mori, which are reared in captivity (sericulture). The shimmery appearance of silk is due to the triangular prism-like structure of the silk fiber, which causes silk cloth to refract incoming light at different angles, thus producing different colors.

Harvested silk is produced by numerous insects; generally, only the silk of various moth caterpillars has been used for textile manufacturing. Research into other types of silk, which differ at the molecular level, has been conducted. Silk is produced primarily by the larvae of insects undergoing complete metamorphosis, but some insects, such as webspinners and raspy crickets, produce silk throughout their lives. Silk production also occurs in hymenoptera (bees, wasps, and ants), silverfish, caddisflies, mayflies, thrips, leafhoppers, beetles, lacewings, fleas, flies, and midges. Other types of arthropods also produce silk, most notably various arachnids, such as spiders.

Lepidoptera (/ˌlɛpɪˈdɒptərə/ LEP-ih-DOP-tər-ə) or lepidopterans are an order of winged insects which include butterflies and moths. About 180,000 species of the Lepidoptera have been described, representing 10% of the total described species of living organisms, making it the second largest insect order (behind Coleoptera) with 126 families and 46 superfamilies, and one of the most widespread and widely recognizable insect orders in the world.

Lepidopterans have several distinctive features, especially coloured scales that cover their bodies, large triangular wings, and a proboscis for drinking nectar. Almost all species have membranous wings. Mating and egg-laying are normally near or on host plants for the larvae. Butterflies and moths undergo complete metamorphosis. The larva is called a caterpillar; it has a cylindrical body with a well-developed head, chewing mouthparts, three pairs of legs and up to five pairs of prolegs. As it grows, it changes in appearance, going through a series of stages called instars. Once mature, it develops into a pupa. A few butterflies and many moth species spin a silk casing or cocoon for protection prior to pupating, while others just go underground. A butterfly pupa, called a chrysalis, has a hard skin, usually with no cocoon. In the pupa, metamorphosis occurs, and a sexually mature adult emerges.

Spider silk is a protein fibre or silk spun by spiders. Spiders use silk to make webs or other structures that function as adhesive traps to catch prey, to entangle and restrain prey before biting, to transmit tactile information, or as nests or cocoons to protect their offspring. They can use the silk to suspend themselves from height, to float through the air, or to glide away from predators. Most spiders vary the thickness and adhesiveness of their silk according to its use.

In some cases, spiders may use silk as a food source. While methods have been developed to collect silk from a spider by force, gathering silk from many spiders is more difficult than from silk-spinning organisms such as silkworms.

Bombyx mandarina, the wild silk moth, is a species of moth in the family Bombycidae. It is the closest relative of Bombyx mori, the domesticated silk moth. The larvae (caterpillars) of both species are called silkworms, famous for producing the fibroinous cocoon that is harvested by humans for silk.

Unlike its domesticated relative, who has lost the ability to fly and is too synanthropic to even survive outside human cultivation, B. mandarina is a fairly ordinary moth. The main difference between the wild B. mandarina and the domesticated B. mori is that the former has a more slender body with well-developed wings in males, and is dull greyish-brown in colour.