Does Silk Really Come from Spiders?

The silk produced by spiders to construct webs and ensnare prey is stronger than steel yet finer than human hair. Composed of protein, it is more elastic and waterproof than regular silk, which is produced by silkworms, yet it would require 27,000 spiders, each spinning an individual web, to produce just 1 pound. Spiders consume their silk when they no longer need it, because its high protein content makes it a sustaining snack.

Silk production begins in the silk glands located in the underside of the spider’s abdomen. Spiders have seven known silk glands, each producing a different type of silk, although the number of glands an individual spider possesses depends on its sex and the species it belongs to. The fluid secreted by the silk glands passes through a labyrinth of microscopic tubes to the spider’s spinnerets (abdominal organs) and exits through the microscopic hairlike protrusions known as spigots, to emerge as a solid silk thread.

Spiders use their silk to construct safety nets that connect them to their webs, build shelters and egg sacs and webs, ensnare prey and weave webs on which to deposit sperm. The texture and chemical composition of the silk is determined by the silk gland from which it is secreted and its precise purpose. The silk that spiders use to ensnare prey, for example, has a sticky quality, while dragline silk, which connects the spider to its web, is the strongest type of arachnid silk because it must support the spider’s weight.

Spiders' silk has never been farmed commercially because the small quantities produced by spiders, combined with their tendency to eat one another, makes this impractical. However, small quantities of spider silk have been used for fishing lines, the cross-hairs of optical instruments and even violin strings. Scientists are keen to produce synthetic materials that mimic the properties of spider silk but have been unable to do so because they still don’t fully understand the exact biological process by which spiders produce silk.

Textiles woven from spider silk are so rare as to be imbued with iconic, mythical status. In 1709, Frenchman François Xavier Bon de Saint Hilaire produced gloves and stockings and reputedly a full suit of clothes for King Louis XIV. In the early 19th century, Napoleon and his wife Josephine were presented stockings and a shawl made by Raimondo de Termeyer, a Spaniard working in Italy. In 2009, a gold cape and a large piece of brocaded fabric, hand-woven from the silk of 1.2 million female golden orb spiders in Madagascar, attracted record numbers of visitors when it went on display at the Natural History Museum in New York. The golden orb spiders were chosen for their unique golden silk threads, which were extracted from their silk glands with machines based on earlier 19th century models. The spiders were not harmed in the process and were released back into the wild after the silk was extracted.