Spider Silk (クモの糸 Kumo no Ito?) is a protein fibre created by spiders for a variety of uses; such as to make webs and other structures that function as nets to catch prey, to create nests or cocoons to protect their offspring, or to utilize in various methods of suspension similar to ropes.
Many small spiders also use spider silk threads for "dynamic kiting"; where a small spider or spiderling let out several threads of silk into the air similar in function to a kite or parachute, and let themselves be carried away by winds.
In some cases, spiders may even use silk as a source of food. Some daily weavers of temporary webs will eat the unused silk at the end of the day as a source of protein to build more webs the following day.
Most silks, in particular dragline silk, have exceptional mechanical properties. They exhibit a unique combination of high tensile strength comparable and extensibility (ductility). This enables a silk fibre to absorb a lot of energy before breaking (toughness), much more than Kevlar or Steel on a weight-to-weight comparison.
Amongst Liminals, both mainstream Arachnes and Small Breed Arachnes are able to produce spider silk as well due to their arachnid physiology. It's common practice amongst Arachnes to weave a wide variety of objects from their own thread, such as clothes, hammocks and dolls. Arachne silk is said to be five times stronger than steel and twice as elastic as nylon.
- All spiders produce silks, and a single spider can produce up to seven different types of silk for different uses.
- A strand of spider silk long enough to circle the Earth would weigh less than 500 grams (18 oz).
- Peasants in the southern Carpathian Mountains used to cut up tubes built by Purse Web Spiders and cover wounds with the inner lining. It reportedly facilitated healing, and even connected with the skin. This is believed to be due to antiseptic properties of spider silk and because the silk is rich in vitamin K, which can be effective in clotting blood.
- Due to the difficulties in extracting and processing substantial amounts of spider silk, the largest known piece of cloth made of spider silk is an 11-by-4-foot (3.4 by 1.2 m) textile with a golden tint made in Madagascar in 2009. Eighty-two people worked for four years to collect over one million golden orb spiders and extract silk from them.