Thinner than cobwebs, but stronger than steel. Riddles of the web Thin threads of the web

The web is the secret of the arachnoid glands, which, shortly after being excreted, freezes in the form of threads. By chemical nature, it is a protein similar in composition to insect silk. This protein is enriched with glycine, alanine and serine. Inside the spider gland, it exists in liquid form. When selected through numerous spinning tubes opening on the surface arachnoid warts, there is a change in the structure of the protein, as a result of which it hardens in the form of a thin thread. Subsequently, the spider intertwines these primary threads into a thicker arachnoid fiber.

The most famous use of the web by spiders is the construction of trapping nets, which, depending on the structure, are able to completely immobilize prey, impede its movement, or only signal its appearance. Caught prey spiders are also often wrapped in a net.

Spiders spin a web that plays a very important role in their lives, and find a variety of uses for it. These are spider cocoons, where tiny cubs develop from eggs in warmth and safety; and lifelines like climbing ropes that attach to plants and keep the spider from falling to the ground. From the web, spiders make nests for the winter and, finally, weave trapping nets.

Spiders can spin different threads for different purposes. If you need a thread for a trapping net, then special glands located next to the cobwebs cover it with a layer of adhesive. To move from place to place or to attach a trapping net, a dry thread is produced. Other glands secrete substances from which a thread is spun to twist a cocoon. The thread of the web is stronger than steel wire of the same diameter and can, without breaking, stretch for another third of its length. In order not to get into its own trapping net, the spider constantly produces a little dry thread. He knows well where the safe areas are, and, hiding in one of them, patiently waits until the victim falls into the net. In addition, the legs of the spider secrete an oily substance, due to which they do not stick to the web.

the spider begins weaving the web, throwing the thread into the wind. The silk flies in the wind and clings to something, such as a tree branch, which allows the spider to climb up this thread and add another thread to the original one to make it stronger. After the spider has made the general contours of the web, he spins a thread connecting one side of the web to the other. From the center of this connecting thread the spider starts spinning another thread, which will connect the center of the web to the side thread.

Then the spider will put a lot of connecting dry threads from the edges of the web along its radii to the center, like spokes in a bicycle wheel. Then these "knitting needles" are braided with circular threads. It turns out a spiral dry web. Then an adhesive thread is applied to the surface of the dry web. Now the spider gets rid of the dry web - eats it. The fishing gear is done, the insect snares are ready.

Spider silk- unusual material. One of its features,with the unusual lightness of the web- great strength.The breaking force, expressed in kg per 1 mm2, in the web of spiders ranges from 40 to 261, and in caterpillar and artificial silk, respectively, does not exceed 43 and 20.A pencil-thin thread of silk can stop a Boeing 747.

Back in the seventeenth century, engineers drew attention to the web, namely, to the fact that it is an exceptionally rational mechanical structure that works in tension in such a way that all threads are in the most favorable conditions in terms of material strength.

Any violation of the nervous system of spiders is immediately reflected in the pattern of the web. Spiders were given various substances, and each time they weaved their own special pattern, which strictly corresponded to a certain substance.

This discovery unexpectedly came in handy in forensic science. By giving a spider a drop of the blood of a person who is suspected to have been poisoned, the nature of the drawing can determine the poison with which the person was poisoned.

Why doesn't a spider get entangled in its web like its victims get entangled in it? And this happens because the spider always runs only along smooth radial threads, and never along sticky, concentric ones.

In Spain, the oldest fossil web with adhering insects (in a piece of amber) was found, the age of which is 110 million years.

Spiders are very sensitive. Their behavior can predict the weather. If spiders develop vigorous activity in the evening - wait for good weather. If this happens in the morning, the weather will be inclement.

The chemical composition of the web is close to the silk of butterfly caterpillars. From the web of nephil spiders, which are found on tropical islands, the Chinese made a durable fabric called "satin of the eastern sea." In Europe, beautiful clothes were sewn from the web.

Polynesian fishermen use the thread of the golden orb-web spider as a fishing line.
Some tribes in New Guinea used nets as hats to protect their heads from the rain.

The weight of the web is such that if the web were to wrap the Earth around the equator once, then its weight would be only 450 grams.

Why does a spider need a web?

Most people think that spiders only use silk to spin their webs. In fact, rarely does an animal use silk in such a versatile way as the spider, which makes houses out of it, weaves "life lines", "diving bells", "airplanes", lasso, elastic traps and the well-known web.

Spiders are not insects, but belong to the arachnid class. Unlike insects, they have eight legs, in most cases eight eyes, no wings, and a body divided into two parts.

Spiders are found in almost any climate. They can run on the ground, climb trees and even live in water. And for this they need a web...

Spider works out different types silks: sticky silk for webs that should trap insects, durable and non-sticky silk for web steps, and special silk for cocoons.

Even the webs woven by spiders come in completely different shapes. The most common is a round web, but there are also square webs, flat and in the form of a funnel or dome. There are webs with lids so that prey does not escape them, some spiders build a house in the form of a bell, located entirely under water.

The spider uses its web when building nets to catch prey, then the spider ties its prey with its thread just in case. Also, a spider can jump or descend without fear with the help of its thread, run along cobwebs, like along paths. Well, and not unimportant, spiders weave cocoons for their eggs from the same silk thread to protect future offspring from unexpected situations that threaten their death.

A spider lives in the jungles of Madagascar, weaving a web that can stretch from one side of a river or lake to another, and the thread it uses consists of the world's strongest biological material. The "Darwin Spider" discovered by Ingi Agnarsson of the University of Puerto Rico, who first encountered such webs in 2001 in Madagascar's Ranamophane National Park, is not particularly large, only 1.5 inches long (with limbs extended), but a web that he weaves - huge. The length of the main thread can reach 80 feet, and the circumference of the web is 9 feet square. The elasticity of the thread is twice that of any other spider thread, and given the fact that its tensile strength is higher than that of steel, the thread of this spider is the strongest naturally occurring material known to science.

Arachnids stand out from all insects with the ability to weave amazing cobweb patterns.
How a spider spins a web is unimaginable. A small creature creates large and strong networks. An amazing ability was formed 130 million years ago.

It is no coincidence that all possibilities in animals appear and are fixed during natural selection. Each action has a strictly defined purpose.

The spider spins a web to achieve vital goals:

• catching prey;
• breeding;
• strengthening their minks;
• fall insurance;
• deception of predators;
• facilitate movement on surfaces.

The order of spiders consists of 42 thousand species, each of which has its own preferences in the use of the arachnoid structure. To hold the victim, the grid is used by all representatives. Males - aranemorphs on the grid leave secretions of seminal fluid. Then the spider on the web walks, collecting secretions on the organs of copulation.

After fertilization, the babies are formed in a protective web cocoon. Some females leave pheromones on the net - substances that attract partners. Spinners wrap threads around leaves and twigs. The result is dummies to distract predators. Silverfish living in the water make houses with air cavities.

The size of the web depends on the type of spider. Some tropical arachnids create "masterpieces" with a diameter of 2 m, capable of holding even a bird. Ordinary spider webs are smaller.
It is interesting to know how much a spider weaves a web. Zoologists managed to find out that the cross-piece copes with the work in a few hours. Representatives of hot countries take several days to create patterns of a large area. main role in the process are carried out by special bodies.

The structure of the spider glands

On the abdomen of the insect there are outgrowths - arachnoid warts with holes in the form of tubes.
Through these ducts, a viscous liquid flows out from the arachnoid gland. When exposed to air, the gel turns into thin fibers.

The chemical composition of the web

The unique ability of the released solution to solidify is explained by the structural components.

The composition of the liquid contains a high concentration of protein containing the following amino acids:

• glycine;
• alanine;
• serine

The quaternary structure of the protein, when pushed out of the duct, changes in such a way that filaments are formed as a result. From the filamentous formations, subsequently, fibers are obtained, the strength of which
4 to 10 times the strength of a human hair.,
1.5 - 6 times stronger than steel alloys.

Now it becomes clear how a spider weaves a web between trees. Thin strong fibers do not break, they are easily compressed, stretched, rotated without twisting, connecting the branches into a single network.

The purpose of the life of a spider is the extraction of protein food. The answer to the question "Why do spiders weave webs" is obvious. First of all, for hunting insects. They make a trapping net of complex design. Appearance patterned structures is different.

• Most often we see polygonal networks. Sometimes they are almost round. Weaving from spiders requires incredible skill and patience. Sitting on the top branch, they form a thread that hangs in the air. If you're lucky, the thread will quickly catch on the branch in suitable place and a spider, will move to a new point for further work. If the thread does not catch in any way, the spider pulls it towards itself, eats it so that the product does not disappear, and begins the process again. Gradually forming a frame, the insect proceeds to create radial foundations. When they are ready, the only thing left is to make connecting threads between the radii;
• Funnel representatives have a different approach. They make a funnel and hide at the bottom. When the victim approaches, the spider jumps out and pulls it into the funnel;
• Some individuals form a network of zigzag threads. The probability that the victim will not get out of such a pattern is much greater;
• The spider with the name "bola" does not bother itself, spins out only one thread, on which there is a drop of glue at the end. The hunter shoots the thread at the victim, sticking it tightly;
• Spiders - ogres were even more cunning. They make a small mesh between the paws, then cast on the desired object.

Designs depend on the living conditions of insects, their species.

Conclusion

Having found out how a spider weaves a web, what are its features, it remains to admire this creation of nature, to try to create something similar. In delicate patterns of knitted shawls, craftswomen copy patterns. Antennas, nets for catching fish and animals are made according to similar schemes. So far, a person has not been able to fully simulate the process.

Video: Spider weaves a web

Anyone can easily brush away the cobwebs hanging between the branches of a tree or under the ceiling in the far corner of the room. But few people know that if the web had a diameter of 1 mm, then it could withstand a load of approximately 200 kg. Steel wire of the same diameter can withstand significantly less: 30–100 kg, depending on the type of steel. Why does the web have such exceptional properties?

Some spiders spin up to seven types of thread, each with its own purpose. Threads can be used not only for catching prey, but also for building cocoons and parachuting (flying up in the wind, spiders can escape from a sudden threat, and young spiders settle in new territories in this way). Each type of web is produced by special glands.

The web used for catching prey consists of several types of threads (Fig. 1): frame, radial, trapping and auxiliary. Most Interest scientists are called by the carcass thread: it has both high strength and high elasticity - it is this combination of properties that is unique. Ultimate stress at break of the skeleton thread of the spider Araneus diadematus is 1.1–2.7. For comparison: the tensile strength of steel is 0.4–1.5 GPa, and that of a human hair is 0.25 GPa. At the same time, the carcass thread is capable of stretching by 30–35%, and most metals can withstand deformation no more than 10–20%.

Imagine a flying insect that hits a stretched web. In this case, the web thread must stretch so that the kinetic energy of the flying insect turns into heat. If the web stored the received energy in the form of elastic deformation energy, then the insect would bounce off the web like from a trampoline. An important property of the web is that it releases a very large amount of heat during rapid stretching and subsequent contraction: the energy released per unit volume is more than 150 MJ / m 3 (steel releases - 6 MJ / m 3). This allows the web to effectively dissipate the impact energy and not stretch too much when the victim is hit. Spider webs or polymers with similar properties could be ideal materials for lightweight body armor.

AT traditional medicine there is such a recipe: on a wound or abrasion, in order to stop the blood, you can attach a web, carefully cleaning it from insects and small twigs stuck in it. It turns out that the web has a hemostatic effect and accelerates the healing of damaged skin. Surgeons and transplantologists could use it as a material for suturing, reinforcing implants, and even as preparations for artificial organs. With the help of the web, it is possible to significantly improve the mechanical properties of many materials that are currently used in medicine.

So, the web is an unusual and very promising material. What molecular mechanisms are responsible for its exceptional properties?

We are accustomed to the fact that molecules are extremely small objects. However, this is not always the case: polymers are widespread around us, which have long molecules consisting of the same or similar friend on the other links. Everyone knows that the genetic information of a living organism is recorded in long DNA molecules. Everyone was holding plastic bags made of long intertwined polyethylene molecules. Polymer molecules can reach huge sizes.

For example, the mass of one molecule of human DNA is about 1.9·10 12 a.m.u. (however, this is about a hundred billion times more than the mass of a water molecule), each molecule is several centimeters long, and the total length of all human DNA molecules reaches 10 11 km.

The most important class of natural polymers are proteins, they consist of units called amino acids. Different proteins perform extremely different functions in living organisms: they control chemical reactions, they are used as a building material, for protection, etc.

The skeleton thread of the web consists of two proteins, which are called spidroins 1 and 2 (from the English spider- spider). Spidroins are long molecules with masses ranging from 120,000 to 720,000 amu. In different spiders, the amino acid sequences of spidroins may differ from each other, but all spidroins have common features. If you mentally stretch a long spidroin molecule into a straight line and look at the sequence of amino acids, it turns out that it consists of repeating sections similar to each other (Fig. 2). Two types of sites alternate in the molecule: relatively hydrophilic (those that are energetically beneficial in contact with water molecules) and relatively hydrophobic (those that avoid contact with water). At the ends of each molecule, there are two non-repeating hydrophilic regions, while the hydrophobic regions are made up of many repeats of an amino acid called alanine.

A long molecule (eg protein, DNA, synthetic polymer) can be represented as a crumpled tangled rope. It is not difficult to stretch it, because the loops within the molecule can be straightened out with relatively little effort. Some polymers (such as rubber) can stretch up to 500% of their initial length. So the ability of a web (a material consisting of long molecules) to deform more than metals is not surprising.

Where does the strength of the web come from?

To understand this, it is important to follow the process of thread formation. Inside the spider's gland, spidroins accumulate as a concentrated solution. When the filament is formed, this solution leaves the gland through a narrow channel, this helps the molecules to stretch and orient them along the direction of the stretch, and the corresponding chemical changes cause the molecules to stick together. Fragments of molecules, consisting of alanines, join together and form an ordered structure similar to a crystal (Fig. 3). Within such a structure, the fragments are stacked parallel to each other and linked to each other by hydrogen bonds. It is these sections, linked together, that provide the strength of the fiber. The typical size of such densely packed regions of molecules is several nanometers. The hydrophilic areas located around them turn out to be randomly folded, similar to crumpled ropes, they can straighten out and thereby provide stretching of the web.

Many composite materials, such as reinforced plastics, are built on the same principle as the carcass thread: in a relatively soft and movable matrix, which allows deformation, there are small hard areas that make the material strong. Although materials scientists have been working with such systems for a long time, human-made composites are only beginning to approach the web in their properties.

Curiously, when the web gets wet, it shrinks a lot (this phenomenon is called supercontraction). This is because water molecules penetrate the fiber and make the disordered hydrophilic regions more mobile. If the web is stretched and sagged from insects, then on a wet or rainy day it shrinks and at the same time restores its shape.

We also note interesting feature thread formation. The spider pulls the web under its own weight, but the resulting web (thread diameter approximately 1-10 microns) can usually support a mass of six times the mass of the spider itself. If, however, the weight of the spider is increased by spinning it in a centrifuge, it begins to secrete a thicker and more durable, but less rigid web.

When it comes to the use of the web, the question arises of how to get it in industrial quantities. In the world there are installations for "milking" spiders, which pull out the threads and wind them on special reels. However, this method is inefficient: in order to accumulate 500 g of web, 27 thousand medium spiders are needed. This is where bioengineering comes to the rescue. Modern technologies make it possible to introduce genes encoding web proteins into various living organisms, such as bacteria or yeast. These genetically modified organisms become sources of artificial webs. Proteins obtained by genetic engineering are called recombinant. Note that usually recombinant spidroins are much smaller than natural ones, but the structure of the molecule (alternation of hydrophilic and hydrophobic regions) remains unchanged.

There is confidence that the artificial web will not be inferior to the natural one in its properties and will find its practical application as a durable and environmentally friendly material. In Russia, several scientific groups from various institutes are jointly engaged in research on the properties of the web. Obtaining a recombinant web is carried out at the State Research Institute of Genetics and Selection of Industrial Microorganisms, the physical and chemical properties of proteins are studied at the Department of Bioengineering, Faculty of Biology, Moscow State University. M. V. Lomonosov, products from web proteins are formed at the Institute of Bioorganic Chemistry of the Russian Academy of Sciences, their medical applications are dealt with at the Institute of Transplantology and Artificial Organs.

In the 18th century, a certain Bon from Montpellier knitted himself a pair of stockings and gloves out of cobwebs. This experience of using a spider web for textile purposes turned out to be the only one. Currently, the web is used only as the crosshairs of precision optical instruments.

The web is synthesized from the amino acids in the spider's blood. This happens in the cells located in the walls of the spider glands. The web is produced in droplets; they merge in the hollow central part of the gland. This viscous liquid is actually a concentrated solution of cobwebs. The solution accumulates in the glands until the spider needs the web and it is pulled from the ducts of the spider warts. The web quickly stretches into a thin thread and immediately passes from a viscous state to a solid one.

Substances that can be drawn into filaments are usually high molecular weight polymers. They are made up of long, thin molecules. Molecules are twisted when they are in solution. However, if they are pulled out of a thin hole, they unfold and are located along the entire length of the fiber. Molecules are held in this position by cross-links that form between adjacent chains.

Moving, the spider usually weaves a double thread - the so-called hanging thread. It keeps it from falling and is attached with attachment discs whenever the spider needs to go down.

The hanging thread is sometimes reinforced with two thinner threads. They are also used for the manufacture of the outer frame and radial threads of the trapping net. Another main part of the trapping net is a spiral thread; it actually captures the flies falling on it.

The entire network is very sticky and extremely elastic. It is sticky due to the many droplets of a very viscous substance that coats both cobwebs and holds them together. At the slightest contact with a viscous thread, the fly sticks. The thread can stretch without breaking, no matter how strong the victim. This usually results in the fly becoming entangled in adjacent sticky threads as well. Holding the fly, the spider rotates it with its jaws, toenails and front legs, while its hind legs pull the web from the spider warts. The fly thus finds itself in a cobweb "bandage", and the spider often takes the victim to its shelter, where it will either be eaten right away or be hung up "in reserve".

There is another web; it is used to make a cocoon. This thread wraps the spider around the eggs laid in autumn. The cocoon protects the eggs from bad weather and encroachments of various predators.

The web is made up of proteins. Proteins are known to play an essential role in the structure and function of all living organisms. They consist of myosin in muscles, collagen in connective tissues, hemoglobin in the blood, as well as enzymes that control all chemical reactions in a living organism.

Proteins are large molecules built from twenty different amino acids. A web protein molecule may consist of one or more chains linked at one or more locations. Strong cross-links are formed by the amino acid cystine, which can "cling" to two different chains. Cystine can also form a link between different parts of the same chain, forming loops.

Twenty amino acids can form a huge number of different proteins. One of the main goals pursued by protein chemists is to determine the number of amino acids in a protein and their relative positions.

To determine the amino acid composition, it is decomposed into its constituent amino acids by boiling in hydrochloric acid. Then all components are isolated from the mixture of amino acids. Twenty-five years ago, this was a rather complicated procedure, requiring a lot of material and time, and besides, it did not always give accurate results. Currently, a complete analysis of amino acids can be performed on a few milligrams of material in one day. Scientists have created an apparatus in which a mixture of amino acids is first decomposed into components, and then their number is automatically recorded and recorded in the form of graphs.

These analytical methods have been applied in the analysis of a number of cobwebs. There is a big difference in the compositions of cocoon thread and hanging thread. The main amino acids of the first are alanine and serine, the second are glycine and alanine. More than half of the protein in each case is formed by only two amino acids, although many other amino acids are present in them. Most of all in the web of amino acids with very short side chains.

Knowing how amino acids are arranged in a protein is very important. But this still does not make it possible to explain all the properties of the fibers. These properties depend to a large extent on how the chains are arranged relative to each other.

In 1913, Father and Son Braggy showed that a crystal of any substance rotated in X-rays reflects them at certain specific angles, since it consists of ordered atoms that form reflection planes. In the same year, two Japanese - Nikishawa and Ono - found that many fibers that were supposed to have no crystalline structure also give certain reflections.

Existing x-rays of arachnoid filaments look inconspicuous when compared with x-rays of true crystals, but they can provide significant information about the structure of the web. The fact that such an X-ray pattern contains spots indicates the presence of crystalline regions in the fibers of the web, which have an ordered arrangement of atoms. The credit for determining the structure of these crystalline regions belongs primarily to Professor Linus Pauling of the California Institute of Technology and Professor Warwicker.

Thanks to these studies, we know that almost all types of webs have a similar structure. A rough idea of ​​​​it can be obtained by drawing several equidistant parallel lines on a piece of paper, and then gathering this sheet into folds at right angles to the lines. The lines represent long peptide chains, and the places where they intersect with the folds indicate the positions of the carbon atoms from which the side chains extend. They go at right angles to the plane of the sheet.

Now consider a number of similar sheets put together; the density of their "packing" will depend on the size of the I-groups. Almost all webs have chains arranged in a similar way within the sheets, and differ only in the distance between the sheets: it ranges from 3.3 to 15.6 angstroms.

The thread of the web under is long, regular cylinders with an almost regular circular cross section. One way to compare the fineness of fibers is to indicate the weight of a particular length of fiber. For a web, it is usually expressed in denier - the weight in grams of 9 kilometers of thread. In this measurement system, a silkworm thread weighs 1 denier, while a human hair weighs 40-50 denier. The weight of the spider cocoon thread is 0.7 denier, and the hanging thread is even less, 0.07 denier. A hanging thread entwined around the globe at the equator would weigh only about 340 grams.

The strength and tensile properties of threads are important for the textile industry. To compare threads of different thicknesses, their strength is usually expressed in terms of tensile strength, that is, in terms of breaking load divided by denier. Tensile strength is thus expressed in grams per denier. The average breaking strength of the cocoon threads is 2.2 g/denier and that of the hanging thread is 7.8 g/denier. The elongation by the time of rupture reaches 46% and 31%, respectively.

Unlike the hanging thread, the cocoon thread is relatively fragile, and this is due to its purpose. She does not have to withstand great stresses, her task is to create protective shell for cocoon eggs. To do this, the spider weaves a six-layer yarn from a curly thread. Each thread of the cocoon consists of six cobwebs. This web shell is reminiscent of the bulky yarn that was developed in last years for the manufacture of elastic knitwear from artificial fibers.

The spiral thread of the trapping net, which forms a sticky web trap, is very elastic. Its expansion and contraction are completely reversible, and in this respect it resembles rubber.

One of the goals of the synthetic materials industry is to provide customers with materials with specific properties. Fabric for underwear, for example, needs to retain heat and absorb moisture, while tire cord needs a very strong fabric.

The development of artificial protein fibers is still in its infancy, because we are not yet able to create long chains with a complex amino acid structure. You can, however, take one amino acid and polymerize it into long chains, such as polyalanine or polyalanine and methyl glutamag, to get good tissues out of them. It is also possible to obtain high molecular weight polymers with a repeating dipeptide sequence, for example, ... glycine - alanine - glycine - alanine - glycine-alanine ...

Further study of various types of webs is the way that will surely help us in creating artificial protein fibers.

P.S. What else are British scientists talking about: that in the future, based on a more detailed, molecular study of both the spider thread and other natural materials, scientists will be able to get various ultra-useful things for our everyday life, for example, heavy-duty
reinforced concrete productsmade from special polymers or something like that.

Stupid question at first glance: of course, steel! breaks at the slightest touch of the hand, and the steel bridge can withstand the weight of hundreds of cars and trucks passing over it. But a spider's web is made up of incredibly thin threads. If steel wire were of the same negligible thickness, the trapping net from it would not even be able to support the weight of her spider. And a bridge built of spider webs would not have collapsed from a busier traffic - and at the same time it would have been much lighter than steel. Spider web is a unique material that combines amazing strength with elasticity. So far, mankind has not succeeded in reproducing it.

Orb-weaving spiders weave their trapping webs according to a strictly defined plan. First of all, they construct a frame in the form of the Latin letter "Y" (1), then strengthen it with additional threads and, finally, weave a sticky spiral to catch insects.

The spider web is formed as a result of the hardening of a viscous fluid that is released from the holes at the top of the spider webs.

Why doesn't a spider get tangled in its own web?

Spider webs are amazing structures. The orb-web spider takes several hours to weave a large spiral web, and almost every day this building is repaired and updated. Caught in a spider web, there is almost no chance to get out of it. And spiders of the genus Nephila (Nephila), also known as banana or giant tree spiders, weave huge webs in which even small birds can get entangled. Woven from elastic heavy-duty silky threads, such a net does not break, but only stretches under the weight of the victim. In addition, the web threads are covered with a thin layer of sticky liquid that holds the insect tightly in the web. The more desperately the victim fights for his freedom, the more he becomes entangled in the web. The spider, sitting in the center of the web, catches the vibrations of the web with its feet, crawls up to the prey and kills it with a chelicera bite. Its owner is not afraid to get entangled in his own web: when constructing a network, he laid “paths” in it from non-adhesive threads. Only these paths are used by the spider, running along its trapping web.