Spider Web: Facts, Types, Components, Pictures

Spider Web

A spider web, often called cobweb, is a structure of thread-like silk created by spiders typically for catching their prey.

What are Spider Webs Made of

As mentioned before, the spider web is made of silk, which is a natural fiber covered with a sticky layer of protein, fatty acids, salts, and organic molecules. Most spider species possess three pairs of silk-spinning glands called spinnerets, which thrust out spider silk. Spiders are able to produce six types of silk, including the ‘fluffy’ capture silk and ‘sticky’ capture silk.

Is a Spider Web Different from a Cobweb

The term ‘spider web’ is generally used by biologists for referring to a structure that is clean and still in use, while the term ‘cobweb’ refers to an abandoned web that has become dusty. Cobweb also indicates the tangled three-dimensional spider webs of some species belonging to the Theridiidae family, which includes Redback spider, Common house spider, Brown widow, and Western black widow.

Types of Spider Webs

A spider species is usually categorized depending on the type of web it weaves. The following are the types of spider webs that are spotted in the wild.

1. Spiral Orb Web

The most common among all the spider webs, it is associated with spiders belonging to the family Araneidae, Tetragnathidae, and Uloboridae. Its design is similar to a spoked wheel. Some species that weave orb webs include

2. Cobweb or Tangle Web

This type of web lacks symmetry, with the threads being joined to support. It is associated with spiders of the Theridiidae family, which includes

  • Ogre-faced Stick Spider
  • House Spider.

3. Funnel Web

It is a flat, horizontal web that has openings at both ends, which provide the spider with an escape route. The following spiders belonging to the Agelenidae family weave funnel webs.

4. Sheet Web

It is a flat sheet of silk with crisscrossed thread, occurring between branches or blades of grass. This type of spider web is associated with the Linyphiidae family, which includes

  • Platform Spider
  • Bowl and Doily Spider

5. Tubular Web

It is similar to a funnel web but found either on the ground or the base of trees. The following are the tube-dwelling spiders that belong to the Segestriidae family.

  • Cellar Spider
  • Snake-back Spider

Video: Spider Making a Web

Q: How strong is a spider web?

Scientists have found out that spider silk of a certain weight is approximately five times stronger than steel of the same weight. Spider silk, being much less dense, has a tensile strength of about 1.3 GPa while that of steel is 1.65 GPa.

Q: Do male spiders spin webs?

Adult male spiders only construct webs needed for courtship and induction of sperms. However males of some species such as the Bowl and Doily Spider and Uloborid Spider build webs.

Q: Do all spiders make webs?

Although all spider species produce silk, only half of them make a web. Spider species, such as crab spider, trap door spider, wolf spider, and jumping spider, do not make webs for hunting prey.

Q: Do spiders eat their webs? Yes, spiders may eat their web regularly to regain some of the energy they had lost while building it. In this way, the protein in spider silk is recycled.

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Ask Smithsonian: How Do Spiders Make Their Webs?

Learning exactly what those spinnerets are doing might just generate a whole new web of understanding

Spiders are skillful engineers, gifted with amazing planning skills and a material that allows them to precisely design rigorous and functional webs.

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The material—spider silk—has chemical properties that make it lustrous, strong and light. It’s stronger than steel and has impressive tensile strength, meaning it can be stretched a lot before it snaps. Scientists have been trying for decades to decode exactly what gives the silk both strength and elasticity, but so far they have found only clues.

Any individual spider can make up to seven different types of silk, but most generally make four to five kinds, says Jonathan Coddington, director of the Global Genome Initiative and senior scientist at the Smithsonian’s National Museum of Natural History.

Spiders use their silk for several purposes, including web-building. That diversity is not hard to imagine, given that Earth hosts 45,749 species of spiders, according to the World Spider Catalog. The number is changing constantly with the frequent discovery of new species.

Why build webs? They serve as “pretty much offense and defense,” says Coddington. “If you’re going to live in a web, it’s going to be a defensive structure,” he says, noting that vibrations in the strands can alert the spiders to predators. Webs are also used to catch prey, says Coddington, whose research has focused in part on spider evolution and taxonomy.

Sometimes spiders eat their own webs when they are done with them, as a way to replenish the silk supply.

Spider silk is made of connected protein chains that help make it strong, along with unconnected areas that give it flexibility. It is produced in internal glands, moving from a soluble form to a hardened form and then spun into fiber by the spinnerets on the spider’s abdomen.

Spiders’ multiple spinnerets and eight legs come in handy for web-building. The architecture of a web is very species-specific, says Coddington. “If you show me a web, I can tell you what spider made it,” he says, adding that spiders “are opinionated” about where they will make a web. Some might be at home in the bottom of a paper cup, while others wouldn’t touch that space.

Most web-building happens under the cover of darkness.

The typical orb weaver spider (the group that’s most familiar to Americans) will build a planar orb web, suspended by seven guy lines attached to leaves, twigs, rocks, telephone poles or other surfaces. Hanging from a leaf or some other object, the spider must get its silk from that point to the other surfaces.

The spider starts by pulling silk from a gland with it fourth leg. The opposite fourth leg is used to pull out multiple strands of silk from about 20 additional silk glands, creating a balloon-like structure. The spider sits patiently, knowing that eventually a warm breeze will take up the balloon, which carries away the first line of silk.

Eventually the balloon’s trailing silk strand snags—and, like an angler with a fish on the line, the spider can feel the hit. It tugs to make sure the silk strand is truly attached, then it pulls out new silk and attaches the strand to whatever it is perched on and starts gathering up the snagged strand, pulling itself towards the endpoint, all the while laying out new silk behind it. That new silk is the first planar line. The spider may do this 20 times, creating a network of dry (not sticky) silk lines arcing in all directions.

The spider then has to determine which of those lines constitute seven good attachment points—they must be in a plane and “distributed usefully around the circle the web will occupy,” says Coddington. The spider cuts away the 13 lines that it won’t use. “Now that you have the seven attachments you need, you no longer need to touch the ground, leaves, twigs, anything . you are in your own, arguably solipsistic, world.”

Then the spider starts to spin its web, a relatively simple and predictable process. It begins at the outside and works its way in, attaching segment by segment with its legs, creating concentric circles and ending with a center spiral of sticky silk that traps much-needed prey—all the energy invested in making the web depletes protein stores.

The sticky stuff merely immobilizes the prey. The coup de grâce comes from the spider’s jaws. “Most spiders attack with their teeth,” says Coddington. “They just wade in and bite the thing to death.” That’s a risky proposition, though, because the prey might not be entirely stuck.

A few families of spiders have developed an alternative mode of offense: the sticky-silk wrap attack. Those spiders lay a strand of sticky silk across the ground. When an insect crosses, the vibration alerts the spider, which then attacks, flicking lines of sticky, strong silk around the insect and wrapping it up until it is fully immobilized. The spider then moves in for the death bite. But this is more of a rarity than a rule in the spider world.

Many researchers are studying spider behavior and spider silk in the hopes of some day being able to farm the material or perhaps replicate it through genetic engineering. The silk could be used, for instance, to increase the strength of body armor, or to create skin grafts. “That would be a great thing for the human race,” says Coddington.

A handful of companies are currently invested in spider silk, including Ann Arbor, Michigan-based Kraig Biocraft Laboratories, a Swedish biotech firm, Spiber Technologies, and a German company, AMSilk, which says it has genetically engineered a protein that is similar to spider silk that is currently being used in shampoos and other cosmetics.

About Alicia Ault

Alicia Ault is a Washington, DC-based journalist whose work has appeared in publications including the New York Times, the Washington Post and Wired. When not chasing down a story from our nation’s capital, she takes in the food, music and culture of southwest Louisiana from the peaceful perch of her part-time New Orleans home.

www.smithsonianmag.com

True Adventures of the Ultimate Spider Hunter — Secrets of Spider Silk

If spider silk came out of a factory, it would be hailed as one of the greatest inventions of all time. Delicate yet amazingly sturdy, strong yet stunningly beautiful, it is a material that brings life and death. A spider’s silk is a web of contradictions and a scientific mystery still waiting to be solved.

As NATURE’s True Adventures of the Ultimate Spider-Hunter shows, spiders use their silk in dazzling ways — from building webs that telegraph the presence of trapped prey to creating barriers against unwanted visitors. Overall, the world’s spiders produce at least seven different kinds of silk, with most species producing five to six types. Silk threads are manufactured in special glands and then extruded from “spinnerets,” which control the thickness. Some spiders have several pairs of spinnerets, each producing a different kind of silk.

In Spider-Hunter, viewers see how spiders put different silks to use. In one scene, a female Tucson blond tarantula weaves a silky cover over her burrow in an attempt to rebuff an amorous male tarantula. Unfortunately, he doesn’t take the hint, and ends up getting eaten. “I’m afraid this male got his female, but not in the way that he was hoping,” says the show’s resident spider expert, Martin Nicholas.

Martin Nicholas examines a golden orb-weaving spider’s web.

Other spiders use a special silk to wrap up precious cargo — their eggs. Egg-case silk protects against predators and parasites. Another kind, called dragline silk, is used to build webs and essentially acts like telegraph wires. The vibrating silk tells the spider exactly where a potential meal has hit the web. This silk is five to six times stronger than steel and can be stretched up to 40 percent of its length without breaking.

In southern Mexico, Nicholas introduces viewers to the golden orb-weaving spider, believed to spin the world’s strongest silk. It can stop a buzzing bee in mid-flight and trap small birds. To demonstrate its toughness, Nicholas throws a ping pong ball into a golden orb’s web. The silk stretches, but doesn’t break. Indeed, Nicholas says that if human spinners were able to weave a thick rope from the golden orb’s silk, it would be strong enough to lift a jumbo jet.

In hopes of learning how to synthesize the strong, supple material, researchers have been trying to unlock the biological secrets of silk. Several teams have sequenced genes that enable spiders to manufacture the substance. One day, those genes might be engineered into cells that are cultured in giant vats and used to make spider silk on an industrial scale.

Some scientists have already learned to synthesize small quantities of silk in the laboratory. Biologist Uri Gat of Hebrew University in Jerusalem, for instance, put one spider silk gene into caterpillar cells and produced vials of tough but elastic thread. Other researchers, at Nexia Biotechnologies near Montreal, Canada, put spider genes into the cells that goats use to produce milk. The result was milk laced with molecules of supple silk many times stronger than steel. Potential uses include super tough fabric for bulletproof vests and extremely strong thread for surgeons.

Not all silk researchers are using genetic engineering. Some are chemists trying to mimic the chemical reactions that produce silk molecules. At the Massachusetts Institute of Technology, for instance, teams of chemists are experimenting with the polymers that give silk its flexibility and durability. So far, however, they’ve had trouble accomplishing what a spider does with apparent ease. Indeed, some spiders can produce yards of silk a day, as they constantly reweave and repair their webs.

So, for the time being, spider silk remains a scientific mystery and a marvel of nature.

www.pbs.org

What’s Stronger Than Steel? Spider Silk

Contributor David Pogue of The New York Times launches a special four-part series on PBS’ «Nova» this Wednesday night called «Making Stuff.» And as we see in this sample from David’s first episode, some of that stuff is VERY STRONG STUFF — and comes from a very unlikely source:

Most people on Navy aircraft carriers are there to practice military maneuvers to protect the country. But I’ve come to the USS John C. Stennis for a completely different purpose.

I’m on a quest to find the world’s strongest material. To see what materials are used in this ship, I’ve brought along a sophisticated metallurgical instrument: A refrigerator magnet.

Steel. Steel. Steel. Steel. Steel. The entire ship is made of steel!

Of all the steel on an aircraft carrier, the steel the pilots probably care most about is the «arresting cable.» When the plane comes in at nearly full power, the tail hook (with luck) will catch onto one of those cables and bring the plane to a quick but gradual stop.

A weakened cable could be fatal. So the Navy takes no chances: After every 120 landings, it throws away that expensive cable.

I thought, surely modern science can offer a material that’s stronger than the steel in those cables — like, maybe, Kevlar, the stuff in bullet-proof vests.

Kevlar is not metal. It’s flexible and it’s stronger than steel, according to Tucker Norton, a ballistics expert at duPont. He demonstrated Kevlar’s strength with the DuPont Bullet Shooter 3000. «Today we’re gonna use this .44 Magnum bullet here against Kevlar XP, we’ll see who wins,» he said.

The Kevlar did not stop the bullet. «Well, not the first layer,» said Norton. «But what’s important is all the layers.» Indeed, the bullet was still within the vest.

Norton told me that a Kevlar rope actually could replace those steel cables on the ship — at a very high cost. But he also mentioned a material that’s stronger yet.

«If you look in a spider web, if you just took one single strand of that spider silk, that strand is stronger than steel as well — a lot like Kevlar,» said Norton. «The problem is, we haven’t figured out how to make that commercially at a large scale.»

He’s not kidding. Actually, it’s pretty darned hard to make spider thread at a small scale.

«It’s sort of the holy grail in terms of fabric, in terms of the richness and the softness,» said Nicholas Godley, who should know. He spent four years in Madagascar making a stunning, one-of-a-kind,11-foot cloth out of spider silk.

It is, he says, the largest sample of spider silk in the world. «And it took 1,063,000 spiders to make.»

And his «team» did it by hand — harnessed on their back, with their abdomens that protrude.

It takes 96 strands to make one thin thread — and a lot of threads to make even a tiny sample.

It feels really, really soft. Yet Godley challenged me to break off a piece.

It’s like pulling a strand of steel — I’m going to break before it does.

Technically, spider dragline silk is five times as strong as steel.

It’s not the same silk as you find in a tie — it’s much stronger and much more elastic than the standard silk you get from a silkworm.

But there’s got to be a faster way to get it.

Which brings us to the weirdest part of this story …

Professor Randy Lewis of the University of Wyoming is a man with a very unusual project. He has been splicing spider genes into goats.

«We take the spider silk gene, we put it in and we attach that piece of DNA that regulates when and where it makes a spider silk protein,» Lewis said.

These high-tech goats give milk the old-fashioned way. Twenty minutes of backbreaking work nets three tablespoons of goat milk.

Clearly, it’s not spider silk yet. First, Lewis’ team removes the fat from the milk, and runs it through an alcohol bath.

And then they’re left with — what? Goat-generated, man-made spider silk.

Now, it doesn’t look to me like something that could stop an aircraft on an aircraft carrier.

«Right, because it’s so fine,» Lewis said. «So the idea would be that you would braid this together to make something that’s an inch or inch and a half or 2 inches in diameter.»

The next step is to see just how strong this silk is. Using a machine that measures how much pulling the thread can take before it snaps, Lewis says his strand of man-made spider silk is stronger than Kevlar, stronger than steel, stronger than carbon fibers. «But we’re not stronger than the natural silk,» he added.

And so, how does a spider’s real silk look on this same test?

«Probably be about 10 times higher,» Lewis said. «They figured it out first, so, you know, we’re still learning from the spiders.»

They own the patent!

Someday soon, goat silk could be used for bulletproof vests with half the weight of Kevlar, and parachute cables, and arresting cables, and artificial ligaments, tendons, and bones for wounded soldiers. No wonder the military is funding his work.

Lewis was asked, aren’t there people he meets at cocktail parties who say he’s doing the work of the devil — messing with genes?

«If you were to ask one of the soldiers who comes back from Iraq, they would very much like to have a way to come back with a complete jaw,» Lewis replied.

Goat-generated spider silk isn’t quite ready for mass production. But Randy Lewis and his goats won’t quit until they get there.

«Hopefully, we come to the one that says we’re stronger than any material that man’s ever made,» lewis said, «and then we’ll go out and have a heck of a party.»

For more info:
• «Nova: Making Stuff» (PBS)
• Spider Silk Proteins (University of Wyoming Research Products Center)
• Kevlar (DuPont)

www.cbsnews.com

How a spider weaves a web — secrets of a thread that is stronger than steel

The spider named Dinopis has a great skill for hunting. Rather than weaving a static web and waiting for its prey, it weaves a small yet highly unusual web that it throws on its prey. Afterwards, it tightly wraps up its prey with this web. The entrapped insect can do nothing to extricate itself. The web is so perfectly constructed that the insect gets even more entangled as it gets more alarmed. In order to store its food, the spider wraps the prey with extra strands, almost as if it were packaging it.

How does this spider make a web so excellent in its mechanical design and chemical structure? It is impossible for the spider to have acquired such a skill by coincidence as is claimed by evolutionists. The spider is devoid of faculties such as learning and memorising and does not have even a brain to perform these things. Obviously, this skill is bestowed on the spider by its creator, Allah, Who is Exalted in Power.

Very important miracles are hidden in the thread of the spiders. This thread, with a diameter of less than one thousandth of a millimetre, is 5 times stronger than a steel wire having the same thickness. This thread has yet another characteristic of being extremely light. A length of this thread long enough to encircle the world would weigh only 320 grams. Steel, a substance specially produced in industrial works, is one of the strongest materials manufactured by mankind. However, the spider can produce in its body a far firmer thread than steel. While man produces steel, he makes use of his centuries-old knowledge and technology; which knowledge or technology, then, does the spider use while producing its thread?

As we see, all technological and technical means at the disposal mankind lag behind those of a spider.

www.islamicity.com

Spider Silk Is Nature’s Miracle Fiber

  • B.A., Political Science, Rutgers University

Spider silk is one of the most miraculous natural substances on Earth. Most building materials are either strong or elastic, but spider silk is both. It’s been described as stronger than steel (which is not quite accurate, but close), more impenetrable than Kevlar, and stretchier than nylon. It withstands a lot of strain before breaking, which is the very definition of a tough material. Spider silk also conducts heat and is known to have antibiotic properties.

All Spiders Produce Silk

All spiders produce silk, from the tiniest jumping spider to the biggest tarantula. A spider has special structures called spinnerets at the end of its abdomen. You’ve probably watched a spider constructing a web, or rappelling from a silk thread. The spider uses its hind legs to pull the strand of silk from its spinnerets, little by little.

Spider Silk Is Made From Protein

But what is spider silk, exactly? Spider silk is a fiber of protein, produced by a gland in the spider’s abdomen. The gland stores silk protein in liquid form, which isn’t particularly useful for building structures like webs. When the spider needs silk, the liquefied protein passes through a canal where it gets an acid bath. As the pH of the silk protein is lowered (as it’s acidified), it changes the structure. The motion of pulling the silk from the spinnerets puts tension on the substance, which helps it harden into a solid as it emerges.

Structurally, silk consists of layers of amorphous and crystalline proteins. The firmer protein crystals give silk its strength, while the softer, shapeless protein provides elasticity. Protein is a naturally occurring polymer (in this case, a chain of amino acids). Spider silk, keratin, and collagen are all formed of protein.

Spiders will often recycle valuable silk proteins by eating their webs. Scientists have labeled silk proteins using radioactive markers and examined new silk to determine how efficiently spiders reprocess the silk. Remarkably, they’ve found spiders can consume and reuse silk proteins in 30 minutes. That’s an amazing recycling system!

This versatile material could have limitless applications, but harvesting spider silk isn’t very practical on a large scale. Producing a synthetic material with the properties of spider silk has long been the Holy Grail of scientific research.

8 Ways Spiders Use Silk

Scientists have studied spider silk for centuries, and have learned quite a bit about how spider silk is made and used. Some spiders can actually produce 6 or 7 kinds of silk using different silk glands. When the spider weaves a silk thread, it can combine these varied kinds of silks to produce specialized fibers for different purposes. Sometimes the spider needs a stickier silk strand, and other times it needs a stronger one.

As you might imagine, spiders make good use of their silk-producing skills. When we think of spiders spinning silk, we usually think of them building webs. But spiders use silk for many purposes.

1. Spiders Use Silk to Catch Prey

The best-known use of silk by spiders is for constructing webs, which they use to ensnare prey. Some spiders, like orb weavers, construct circular webs with sticky threads to snag flying insects. Purse web spiders use an innovative design. They spin an upright silk tube and hide inside it. When an insect lands on the outside of the tube, the purse web spider cuts the silk and pulls the insect inside. Most web-weaving spiders have poor eyesight, so they sense prey in the web by feeling for vibrations traveling across the silk strands. A recent study showed that spider silk can vibrate at a wide range of frequencies, allowing the spider to sense movements «as small as a hundred nanometers—1/1000 the width of a human hair.»

But that’s not the only way spiders use silks to catch meals. The bolas spider, for example, spins a sort of fishing line of silk – a long thread with a sticky ball at the end. When an insect passes by, the bolas spider flings the line at the prey and hauls in its catch. Net-casting spiders spin a small web, shaped like a tiny net, and hold it between their feet. When an insect comes near, the spider throws its silk net and ensnares the prey.

2. Spiders User Silk to Subdue Prey

Some spiders, like cobweb spiders, use silk to subdue their prey completely. Have you ever watched a spider grab a fly or moth, and quickly wrap it in silk like a mummy? Cobweb spiders have special setae on their feet, which enable them to wind sticky silk tightly around a struggling insect.

3. Spiders Use Silk to Travel

Anyone who read Charlotte’s Web as a child will be familiar with this spider behavior, known as ballooning. Young spiders (called spiderlings) disperse soon after emerging from their egg sac. In some species, the spiderling will climb onto an exposed surface, raise its abdomen, and cast a silk thread into the wind. As the air current pulls on the silk strand, the spiderling becomes airborne and can be carried for miles.

4. Spiders Use Silk to Keep From Falling

Who hasn’t been startled by a spider descending suddenly on a silk thread? Spiders habitually leave a trail of silk line, known as a dragline, behind them as they explore an area. The silk safety line helps the spider keep from falling unchecked. Spiders also use the dragline to descend in a controlled manner. If the spider finds trouble below, it can quickly ascend the line to safety.

5. Spiders Use Silk to Keep From Getting Lost

Spiders can also use the dragline to find their way home. Should a spider wander too far from its retreat or burrow, it can follow the silk line back to its home.

6. Spiders Use Silk to Take Shelter

Many spiders use silk to construct or reinforce a shelter or retreat. Both tarantulas and wolf spiders dig burrows in the ground and line their homes with silk. Some web-building spiders construct special retreats within or adjacent to their webs. Funnel weaver spiders, for example, spin a cone-shaped retreat in one side of their webs, where they can stay hidden from both prey and predators.

7. Spiders Use Silk to Mate

Before mating, a male spider must prepare and ready his sperm. Male spiders spin silk and construct small sperm webs, just for this purpose. He transfers sperm from his genital opening to the special web and then picks up the sperm with his pedipalps. With his sperm securely stored in his pedipalps, he can search for a receptive female.

8. Spiders Use Silk to Protect Their Offspring

Female spiders produce particularly tough silk to construct egg sacs. She then deposits her eggs inside the sac, where they will be protected from the weather and potential predators as they develop and hatch into tiny spiderlings. Most mother spiders secure the egg sac to a surface, often near her web. Wolf spiders don’t take chances and carry the egg sac around until the offspring emerge.

www.thoughtco.com

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