Spider Silk Stronger than Steel

How beautiful a spider web looks covered in dew, sparkling in the morning sun. And how fragile. A mere brush of your hand will tear it apart. 

 Photo by Luc Viator

Photo by Luc Viator

Would it surprise you to learn that, for its weight, spider web silk is stronger and tougher than steel? A web made of strands of silk as thick as a pencil could stop a Boeing 747 in flight. Scientists are trying to replicate its properties for use in bulletproof vests.

 Spider spinneret

Spider spinneret

It has other beneficial properties as well. In WWII, the U.S. army made crosshairs on sighting devices from the silk of the black widow spider. People used to put spider webs on wounds to staunch the blood, unaware that the silk contains Vitamin K, which helps reduce bleeding. More recently, the silk has been used as a scaffold for growing human skin cells.

This versatile material emerges from flexible spinnerets that allow the spider to direct the flow of silk without having to move its whole body. The silk comes out as a liquid, but it hardens as soon as it comes in contact with the air. Different types of silk glands create different type of silk: smooth, sticky, dry or stretchy.

Spiders use their silk in some ingenious ways. Many stay attached to a line of silk in case they fall. They run up it if they need to escape and use it to sail through the air.

In order to live underwater, the water spider constructs a “diving bell” with its silk. The bell is filled with air bubbles collected at the water’s surface which can last up to a day before they need to be replenished. Inside the bell, the spider uses its legs to pull in insects, tadpoles and small fish.

The bolas spider swings a “fishing line” of thick silk thread with a sticky droplet at the end to catch moths. The ogre-faced spider weaves a net between its front legs, then dangles above a promising spot to scoop up its prey.

Net-throwing spiders do exactly that – they make a small net to throw over their quarry. And some spiders keep it simple. They fire out a sticky gum through their fangs to reel in dinner.

Spiders are the only group of animals to build webs. We’re probably most familiar with the orb web, but there are also other kinds, such as sheets, tangles and ladders. 

 Photo by Fir0002/Flagstaffotos

Photo by Fir0002/Flagstaffotos

A web is sticky because the spider deposits glue droplets on it. The glue is electrically conductive, which allows the web to spring towards its prey. Web-weaving spiders have 2 or 3 claws at the tip of each leg that they use to swing from strand to strand. A spider’s body has an oily substance that keeps it from getting stuck in its web.

Drugs can affect the way a spider spins its web. Spiders on LSD spin beautiful webs. Those spun by caffeinated spiders are terrible. More importantly, scientists believe that examining the shape of a spider’s web could help detect airborne chemicals and pollutants.

While most spiders build a new web every day, the web of the gold orb spider can last several years and is strong enough to catch birds.

Some spiders are very economical. They eat their webs and then reuse them. Hummingbirds do their bit for recycling by using abandoned webs (cobwebs) to weave their nests.

Still think a spider web is delicate? In places like India, you can find communal webs that cover trees for several miles. The Darwin bark spider creates the strongest material made by a living organism. Their giant webs can span rivers, streams and even lakes.

 Several Darwin's bark spider  (Caerostris darwini ) webs spanning a river. Source.

Several Darwin's bark spider (Caerostris darwini) webs spanning a river. Source.

Spider silk and spider webs are pretty amazing. Check out these sites if you’d like to learn more: