Spider Silk

Who among us hasn't been walking somewhere, only to be suddenly entangled in a spider's web, often plastered unpleasantly across our face? As the season progresses and the spiders mature, the evidence for numerous different species in our environment increases.

Around the Nature Center, funnel webs are quite apparent and their makers, the grass spiders, can usually be found hidden within the funnels. Orb webs of the Silver Argiope can sometimes be found attached to the pads of Prickly Pear. These webs often have several radiating silk zig-zag bands near the center. The large spider hangs head down in the center of the web, its legs aligned with any zig-zag bands. Cyclosa spiders are often found on Broom. Their smaller, more delicate orb webs are characterized by a string of debris, usually consisting of insect remains and old skins, running vertically through the center of the web. Careful examination of this debris string will often reveal the small spider near the center of the web. Besides making webs, spiders use silk for many purposes such as dispersal by ballooning and egg sacs. Many spiders, such as the jumping spiders and crab spiders, are overlooked because they do not make the traditional spider webs but use more active hunting techniques. The lime-colored Green Lynx Spider common around the Center is also a hunting spider.

The fine quality of spider silk has been recognized for centuries, a few pairs of gloves and stockings having been made from it as far back as the early sixteenth century. Spider silk is as strong as Kevlar but much more elastic. While various attempts have been made to produce it commercially, these have proven uneconomic partly because of the need to separate the spiders and partly because they are not as productive as silkworms. New efforts are currently underway as people identify applications which require strong, elastic fibers. These include such diverse areas as materials for bulletproof vests and replacement tissues for tendons and ligaments. Advanced techniques, including molecular biology, are being used to determine the exact composition of spider silk and the changes that it undergoes as the liquid proteins inside the spider become the familiar silken web.

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Ron Lyons (volunteer 1990-1999)
Chula Vista Nature Center, 1000 Gunpowder Point Drive, Chula Vista, CA 91910-1201