Next time you see a spiders web, take a closer look before you brush it away. We all know that silkworms are valued for the fibres they spin, but spiders are doing much the same thing.
Spiders webs and silk from silkworms are both made from protein material called fibroin. Silkworms and spiders hold concentrated solutions of the protein in glands inside their bodies. They squirt this out through narrow openings, forming thin filaments that ¢ dry very quickly. The solutions have concentrations of between 15% and 30% so crystallise easily, but only outside the creature. The squirting process forces the molecules to line up so they pack together in crystalline fibres.
Different creatures produce different types of fibroin. Individual creatures can also tailor fibres to suit different purposes by changing the make up of their fibroin. Cocoon silk is more stretchy than the silk used in webs. The silk used in webs is stronger than steel of the same diameter.
Protein is a valuable commodity. Spiders recycle it by eating the silk wrapping along with the prey trapped inside.