Blog: Worldwide Web of Spiders

Orb Spider

Spiders are remarkable. They have been on our planet for 400 million years. The story of how 34,000 species of spiders inhabit our Earth is intriguing.

Spiders are found almost everywhere – from the Arctic Islands to dry deserts, from the tops of tropical mountains to the valley bottoms of the Santa Monica Mountains.

Spiders have devised an ingenious ballooning method where they stand on tip-toes facing the wind and their abdomen reels out silk, like a fisherman playing a game-fish – allowing them to travel up to 60 miles on one silk line.

They’ve even conquered remote Pacific Islands by hitchhiking on driftwood.

Spiders can go up to 200 days without food.

However, when they do get food some spiders like to wrap their prey in silk before eating them. It’s not that dissimilar to some people, who like to wrap their lunch in a soft-shelled taco.

A spider’s blood, called hemolymph, is rich with copper pigments giving it a bluish color. One molecule of spider hemolymph has more than 600 amino acids-the building blocks of protein.

Because there are 34,000 different species of spiders, many of them have different characteristics. For example, water spiders live underwater by enclosing their abdomen in an air bubble and orb spiders have impressive webs. Wolf spiders are ruthless hunters while pirate spiders hunt insects on top of water. Crab spiders ambush prey by moving sideways and jumping spiders pounce prey like a cat. Spitting spiders spew venom that glues helpless prey to the ground prior to lethal paralysis. Bolas spiders throw a sticky drop at male Spodotera moths fooling them to believe it’s a female scent before throwing a bolas web over top of them.

About 30 species of spiders contain poison lethal to humans. Black widows, the Australian funnel-web, the American brown, two kinds of European water spiders and the very aggressive South American ctenids spiders contain venom that attacks and discombobulates the human central nervous system. If bitten an antidote must be taken in order to obviate a fatality.

In most cases, however, spider bites are less dangerous to humans than bee venom.

Spider poison paralyzes its prey–mainly insects. Defensive bites against large animals, including people, are only secondary.

The poison is administered through the fangs. Either the spider crunches its prey immediately or after its been wrapped in silk, it sucks out the insides of its prey through the fang holes – much like a straw draining the last drop from a soda bottle.

Some people loath spiders. Perhaps it’s because they are extremely hairy. Tarantulas are the hairiest of all spiders. They use their hair as a defense mechanism, brushing off clouds of abdominal hair with their hind legs. Each hair is covered by hundreds of microscopic hooks causing severe itching when in contact with skin especially the nose and eye region.

Spider feet are covered in hairs, which in turn may have up to 1,000 extensions. About 160,000 contact points enable spiders to walk perpendicular or upside down on glass.

Like humans, the behavior of spiders is controlled by their central nervous system. Spiders rely upon mechano-receptors vibrations and air currents to make a living. Spiders also have a sense of taste and smell and can also exhibit a capacity to learn.

Most spiders are active during the night and depend upon touch and smell to assist them in finding a mate and recognizing prey and predators. Over 1,000 hairs on the front set of legs are very sensitive to chemical odors.

All spiders produce silk. Spider silk is awesome. It is stronger than bone, tendon or cellulose (wood). Only steel–smelted iron-ore is stronger. Spider’s silk is robust because it’s made up of multiple proteins and water, which gives it incredible elasticity.

A spider’s silk dragline maintains its configuration for 60 miles before rupturing under its own weight.

Spiders are extraordinary engineers. In just a half-hour at night, with the sense of touch not sight, they are able to spin 66 feet of silk web. The entire web weighs no more than between 0.1 and 0.5 milligrams yet it is able to easily hold a spider weighing in excess of 500 milligrams.

Spiders are so worthy of our admiration!

Earth Dr Reese Halter is a broadcaster, conservation biologist and author of The Incomparable Honeybee.