The Book of the Bizarre: Freaky Facts and Strange Stories (12 page)

• Only about half of all spider species spin webs to catch their prey.
  
• All spider webs are made of silk. Although it's only about 0.00012 inch in diameter, a spider's silk is stronger than steel of equal diameter. It is more elastic than nylon, more difficult to break than rubber, and is bacteria and fungi resistant. These qualities explain why at one time webs were used to pack wounds to help them stop bleeding.
  
• Spiders have one to six kinds of spinning glands, each producing a different type of silk. For instance, the cylindrical gland produces silk used for egg sacs (males often lack this particular gland), and the aciniform gland produces silk used for wrapping prey. Some spiders have glands that produce very fine silk. They comb and tease the fine strands
  until they are like Velcro—tiny loops and hooks that entrap insect feet.
  
• Silk is extruded through special pores called spinneretes, which consist of different-sized “spigots.” Silk starts out as a liquid. As the liquid silk contacts the air, it hardens. The spider may need different silk for different purposes. By changing how fast the liquid is extruded or by using a different silk gland, it can control the strength and quality of the silk.
  
• Why doesn't a spider get stuck on its own web? The spider weaves in nonsticky silk strands and only walks on those. Also, spiders have special oil on their legs that keeps them from sticking to the silk.
  

THE WELL-BRED SPIDER

A spider can often be identified by the type of web it weaves. The ability to weave is inherited, so specific types of spiders build specific types of webs. In addition, individual spiders sometimes develop a personal style, sort of like a signature.

The spider is a hunter, and its web is a snare designed to hold its prey. So the design of its web and the place where the spider builds it depend on the kind of insects it is trying to catch. There are more insects, especially crawling ones, closer to the ground. Spiders
often spin webs across ground litter such as leaves and fallen branches where an unsuspecting insect may crawl. Strong flying insects are usually higher, so webs built high are stronger than those built in low spots.

WEB SPINNERS

There are five different types of web-spinning spiders. One kind is cobweb spiders, such as black widows. They use their webs as “trip lines” to snare prey. From their web, several vertical lines are drawn down and secured tautly to a surface with globs of “glue.” Insects get stuck to the glue and break the line. The tension of the elastic trip lines, once released, flings the victim up to the spider waiting in its web. Cobweb weavers usually build only one web and so, with time, the web becomes tattered and littered with bits of debris.

The second kind of web spinner is called a sheetbuilder. They construct a horizontal mat beneath a horizontal trip line, much like a trampoline under an invisible wire. Flying or jumping insects that are stopped midair by the line are flung to the net below, and as the prey struggles to regain its balance, the agile spider pounces and inflicts a deadly bite.

Web-casting spiders, such as ogre-faced spiders, are the third kind of web spinner. They use “web snares”
much differently than others. Instead of attaching the web to a bush or a wall, the spider carries it. The spider uses the web much like a fishing net and casts it on passing prey. The spider hunts every night and afterward will either tuck the web away until the next day's hunt or spin a new one.

Then there are the angle lines, such as the bola spider. It first suspends itself from a trapeze line and hangs there upside down. Then it sends down a single line baited with a glob of glue. When an insect moves by, the bola takes careful aim and casts the line toward the insect. If successful, it will reel in its prize easily.

Lastly, there are orb weavers. These weavers spin the largest and strongest webs. Some webs span more than one meter. Natives of New Guinea and the Solomon Islands used the webs of the orb-weaving spiders as fishing nets. These webs were reportedly strong enough to hold a fish weighing as much as a pound. These webs are especially tailored to capture flying insects, which is why they're vertically suspended. Many orb weavers meticulously take down their webs each day and build a new one at night.

Orb weavers spin such intricate webs that they are often the focus of behavioral studies. For example, two orb weavers went along on Sky Lab II on July 28, 1973.
Researchers were interested to know the effects of zero gravity on the spiders' weaving ability. After some adjustments, the spiders were able to weave fairly normal webs. One curious difference was that the space webs were symmetrical, while earth webs tend to be asymmetrical.

RECLUSIVE STILL

Only eight hundred deaths from brown recluse spiders have been verified in medical literature since 1965, but more than eight hundred death certificates list a cause of death as “hemolytic anemia,” an allergic reaction to—the bite of the brown recluse.

TRUE SLOTH

In 2007, after three years of failed attempts to entice a sloth into budging as part of an experiment in animal movement, scientists in the eastern German city of Jena gave up. The sloth, named Mats, was remanded to a zoo after consistently refusing to climb up and then back down a pole as part of an experiment conducted by scientists at the University of Jena's Institute of Systematic Zoology and Evolutionary Biology.

Neither pounds of cucumbers nor plates of homemade spaghetti were appetizing enough to make Mats move. Mats's new home is the zoo in the northwestern city of Duisburg where, according to all reports, he is very comfortable.

A rat can last longer without water than a camel. Rats can also hold their breath for three minutes and tread water for three days.