Spider Silk

 

Marbled Orbweaver, Araneus marmoreus

All spiders produce silk though not necessarily webs. This orbweaver looks like an eight-handed pianist playing music in cords rather than chords, barely visible until they trap dewdrops and startle the landscape.

Orb-woven cobwebs

Most of this intricate work is accomplished under protection of darkness. Its bejeweling at dawn temporarily defeats the lethal secrecy of the web.

A grass spider Agelenopsis pennsylvanica approaches a lasioglossum bee caught in its web

Funnel weavers create sturdy if less exquisite tangle webs that include a hiding tunnel where they can escape the attention of both predators and prey.

Enshrouded goldenrod, the web scaffold

Consisting of mainly protein, silks are about a sixth of the density of steel. A strand long enough to circle the Earth would weigh about 4.4 pounds. *

Enoplognatha, a Space-filling Web Builder

The silk is produced in glands as a liquid gel that travels down a tube and out through valves that control its thickness and flow. It hardens in contact with air. Most spiders have 6 spinnerets capable of producing silk with different properties for different purposes.

Most silks, in particular dragline silk, have exceptional mechanical properties. They exhibit a unique combination of high tensile strength and extensibility (ductility) which defines toughness‒the ability to absorb a large amount of energy before breaking.

A Common Stretch Spider Tetragnatha extensa consuming a dragonfly

Swathing bands of silk in combination with immobilizing venom preserve prey in the spider's larder.

Among the versatile complexities of web construction are adhesive variations enabling the spider to bind the pattern at intersections, add glue-like properties for capturing prey, and weave in non-sticky threads for its own travel lines.

A Tuftlegged Orbweaver, Mangora placida

The term "spinning" is misleading because no rotation of any component occurs. Silk production is similar to extrusion, with the subtle difference that the force is induced by pulling at the finished fiber rather than being squeezed out of a reservoir. It must first be attached to an anchor point. Then depending on its various uses‒and the chemistry imparted by different silk glands‒the spider can balloon out on a lifeline into space or weave intricate patterns.

Spider silk is of great interest to research scientists trying to unlock its secrets for commercial, military, and medical applications. It continues to be available as a natural wonder for people of all ages.

 

* I am indebted to a Wikipedia article by this name for factual material.