Spider web
Encyclopedia
A spider web, spiderweb, spider's web or cobweb (from the obsolete word coppe, meaning "spider") is a device built by a spider
out of protein
aceous spider silk
extruded from its spinnerets.
Spider webs have existed for at least 140 million years, as witnessed in a rare find of Early Cretaceous
amber
from Sussex
, southern England
.
Insects can get trapped in spider webs, providing nutrition to the spider; however, not all spiders build webs to catch prey
, and some do not build webs at all. The main difference between spider webs and cobwebs is that spider webs are still in use, while cobwebs are webs that have been abandoned.
When spiders moved from the water to the land in the Early Devonian period, they started making silk to protect their bodies and their eggs. Spiders gradually started using silk for hunting purposes, first as guide lines and signal lines, then as ground or bush webs, and eventually as the aerial webs which are so famous today.
Spiders produce silk from their spinneret
glands located at the tip of their abdomen
. Each gland produces a thread for a special purpose – for example a trailed safety line, sticky silk for trapping prey or fine silk for wrapping it. Spiders use different gland types to produce different silks, and some spiders are capable of producing up to 8 different silks during their lifetime.
Most spiders have three pairs of spinnerets, each having its own function – there are also spiders with just one pair and others with as many as four pairs.
Webs allow a spider to catch prey without having to expend energy by running it down.
Thus it is an efficient method of gathering food. However, constructing the web is in itself an energetically costly process because of the large amount of protein required, in the form of silk. In addition, after a time the silk will lose its stickiness and thus become inefficient at capturing prey. It is common for spiders to eat their own web daily to recoup some of the energy used in spinning. The silk proteins are thus recycled.
The tensile strength
of spider silk is greater than the same weight of steel
and has much greater elasticity
. Its microstructure is under investigation for potential applications in industry, including bullet-proof vests and artificial tendons. Researchers have used genetically modified mammals to produce the proteins needed to make this material.
There are a few types of spider webs found in the wild, and many spiders are classified by the webs they weave. Different types of spider webs include:
Several different types of silk
may be used in web construction, including a "sticky
" capture silk and "fluffy" capture silk, depending on the type of spider. Webs may be in a vertical plane (most orb webs), a horizontal plane (sheet webs), or at any angle in between. It is hypothesized that these types of aerial webs co-evolved with the evolution of winged insects. As insects are spiders' main prey, it is likely that they would impose strong selectional forces on the foraging behavior of spiders. Most commonly found in the sheet-web spider families, some webs will have loose, irregular tangles of silk above them. These tangled obstacle courses serve to disorient and knock down flying insects, making them more vulnerable to being trapped on the web below. They may also help to protect the spider from predators such as birds and wasps.
Many webs span gaps between objects which the spider could not cross by crawling. This is done by letting out a first fine adhesive thread to drift on the faintest breeze across a gap. When it sticks to a suitable surface at the far end, the spider will carefully walk along it and strengthen it with a second thread. This process is repeated until the thread is strong enough to support the rest of the web.
After strengthening the first thread, the spider will continue to make a Y-shaped netting. The first three radials of the web are now constructed. More radials are added, making sure that the distance between each radial is small enough to cross. This means that the number of radials in a web directly depends on the size of the spider plus the size of the web.
After the radials are complete, the spider will fortify the center of the web with about five circular threads. Then a spiral of non-sticky, widely spaced threads is made for the spider to easily move around its own web during construction, working from the inside out. Then, beginning from the outside in, the spider will methodically replace this spiral with another, more closely spaced one of adhesive threads. It will utilize the initial radiating lines as well as the non-sticky spirals as guide lines. The spaces between each spiral will be directly proportional to the distance from the tip of its back legs to its spinners. This is one way the spider will use its own body as a measuring/spacing device. While the sticky spirals are formed, the non-adhesive spirals are removed as there is no need for them anymore.
After the spider has completed its web, it will chew off the initial three center spiral threads then sit and wait. If the web is broken without any structural damage during the construction, the spider does not make any initial attempts to rectify the problem.
The spider, after spinning its web, will then wait on or near the web for a prey animal to become trapped. The spider senses the impact and struggle of a prey animal by vibrations transmitted through the web. A spider positioned in the middle of the web makes for a highly visible prey for birds and other predators, even without web decorations
. Many day-hunting orb-web spinners reduce this risk by hiding at the edge of the web with one foot on a signal line from the hub or by appearing to be inedible or unappetizing.
Spiders do not usually adhere to their own webs, because they are able to spin both sticky and non-sticky types of silk, and are careful to travel across only non-sticky portions of the web. However, they are not immune to their own glue. Some of the strands of the web are sticky, and others are not. For example, if a spider has chosen to wait along the outer edges of its web, it may spin a non-sticky prey or signal line to the web hub to monitor web movement.
s) or running them down in open chase (e.g. wolf spider
s). The net-casting spider
balances the two methods of running and web spinning in its feeding habits. This spider weaves a small net which it attaches to its front legs. It then lurks in wait for potential prey and, when such prey arrives, lunges forward to wrap its victim in the net, bite and paralyze it. Hence, this spider expends less energy catching prey than a primitive hunter such as the Wolf spider. It also avoids the energy loss of weaving a large orb web.
Some spiders manage to use the signaling-snare technique of a web without spinning a web at all. Several types of water-dwelling spiders will rest their feet on the water's surface in much the same manner as an orb-web user. When an insect falls onto the water and is ensnared by surface tension
, the spider can detect the vibrations and run out to capture the prey.
In traditional European medicine, cobwebs are used on wounds and cuts and seem to help healing and reduce bleeding.
Cobweb paintings, which began during the 16th century in a remote valley of the Austrian Tyrolean Alps, were created on fabrics consisting of layered and wound cobwebs, stretched over cardboard to make a mat, and strengthened by brushing with milk diluted in water. A small brush was then used to apply watercolor to the cobwebs, or custom tools to create engravings. Fewer than a hundred cobweb paintings survive today, most of which are held in private collections.
It is common for webs to be about 20 times the size of the spider building it. Spider webs are rich in vitamin K, which can be effective in clotting blood. Webs were used several hundred years ago as gauze pads to stop an injured person's bleeding.
, used in optical communications. These optical disturbances are detected in the form of diffraction patterns.
Occasionally, a group of spiders may build webs together in the same area. One such web, reported in 2007 at Lake Tawakoni State Park
in Texas
, measured 200 yards (182.9 m) across. Entomologists believe it may be the result of social cobweb spider
s or of spiders building webs to spread out from one another.
There is no consensus on how common this occurrence is.
Spider webs were spun in low earth orbit
in 1973 aboard Skylab
, involving two female European garden spider
s (cross spiders) called Arabella and Anita, as part of an experiment on the Skylab 3
mission. The aim of the experiment was to test whether the two spiders would spin webs in space, and, if so, whether these webs would be the same as those that spiders produced on Earth. The experiment was a student project of Judy Miles of Lexington, Massachusetts
.
After the launch on July 28, 1973, and entering Skylab, the spiders were released by astronaut
Owen Garriott into a box that resembled a window frame. The spiders proceeded to construct their web while a camera took photographs and examined the spiders' behavior in a zero-gravity
environment. Both spiders took a long time to adapt to their weightless existence. However, after a day, Arabella spun the first web in the experimental cage, although it was initially incomplete.
The web was completed the following day. The crew members were prompted to expand the initial protocol. They fed and watered the spiders, giving them a house fly. The first web was removed on August 13 to allow the spider to construct a second web. At first, the spider failed to construct a new web. When given more water, it built a second web. This time, it was more elaborate than the first. Both spiders died during the mission, possibly from dehydration
.
When scientists were given the opportunity to study the webs, they discovered that the space webs were finer than normal Earth webs, and although the patterns of the web were not totally dissimilar, variations were spotted, and there was a definite difference in the characteristics of the web. Additionally, while the webs were finer overall, the space web had variations in thickness in places: some places were slightly thinner, and others slightly thicker. This was unusual, because Earth webs have been observed to have uniform thickness.
Spider
Spiders are air-breathing arthropods that have eight legs, and chelicerae with fangs that inject venom. They are the largest order of arachnids and rank seventh in total species diversity among all other groups of organisms...
out of protein
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
aceous spider silk
Spider silk
Spider silk is a protein fiber spun by spiders. Spiders use their silk to make webs or other structures, which function as nets to catch other animals, or as nests or cocoons for protection for their offspring...
extruded from its spinnerets.
Spider webs have existed for at least 140 million years, as witnessed in a rare find of Early Cretaceous
Early Cretaceous
The Early Cretaceous or the Lower Cretaceous , is the earlier or lower of the two major divisions of the Cretaceous...
amber
Amber
Amber is fossilized tree resin , which has been appreciated for its color and natural beauty since Neolithic times. Amber is used as an ingredient in perfumes, as a healing agent in folk medicine, and as jewelry. There are five classes of amber, defined on the basis of their chemical constituents...
from Sussex
Sussex
Sussex , from the Old English Sūþsēaxe , is an historic county in South East England corresponding roughly in area to the ancient Kingdom of Sussex. It is bounded on the north by Surrey, east by Kent, south by the English Channel, and west by Hampshire, and is divided for local government into West...
, southern England
England
England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...
.
Insects can get trapped in spider webs, providing nutrition to the spider; however, not all spiders build webs to catch prey
Predation
In ecology, predation describes a biological interaction where a predator feeds on its prey . Predators may or may not kill their prey prior to feeding on them, but the act of predation always results in the death of its prey and the eventual absorption of the prey's tissue through consumption...
, and some do not build webs at all. The main difference between spider webs and cobwebs is that spider webs are still in use, while cobwebs are webs that have been abandoned.
Silk production
Spiders produce silk from their spinneret
Spinneret
A spinneret is a spider's or insect larva's silk-spinning organ. It is usually on the underside of a spider's abdomen, to the rear. While most spiders have six spinnerets, some have two, four, or eight. They move independently and in concert...
glands located at the tip of their abdomen
Abdomen
In vertebrates such as mammals the abdomen constitutes the part of the body between the thorax and pelvis. The region enclosed by the abdomen is termed the abdominal cavity...
. Each gland produces a thread for a special purpose – for example a trailed safety line, sticky silk for trapping prey or fine silk for wrapping it. Spiders use different gland types to produce different silks, and some spiders are capable of producing up to 8 different silks during their lifetime.
Most spiders have three pairs of spinnerets, each having its own function – there are also spiders with just one pair and others with as many as four pairs.
Webs allow a spider to catch prey without having to expend energy by running it down.
Thus it is an efficient method of gathering food. However, constructing the web is in itself an energetically costly process because of the large amount of protein required, in the form of silk. In addition, after a time the silk will lose its stickiness and thus become inefficient at capturing prey. It is common for spiders to eat their own web daily to recoup some of the energy used in spinning. The silk proteins are thus recycled.
The tensile strength
Tensile strength
Ultimate tensile strength , often shortened to tensile strength or ultimate strength, is the maximum stress that a material can withstand while being stretched or pulled before necking, which is when the specimen's cross-section starts to significantly contract...
of spider silk is greater than the same weight of steel
Steel
Steel is an alloy that consists mostly of iron and has a carbon content between 0.2% and 2.1% by weight, depending on the grade. Carbon is the most common alloying material for iron, but various other alloying elements are used, such as manganese, chromium, vanadium, and tungsten...
and has much greater elasticity
Elasticity (physics)
In physics, elasticity is the physical property of a material that returns to its original shape after the stress that made it deform or distort is removed. The relative amount of deformation is called the strain....
. Its microstructure is under investigation for potential applications in industry, including bullet-proof vests and artificial tendons. Researchers have used genetically modified mammals to produce the proteins needed to make this material.
Types of spider webs
- Spiral orb webs, associated primarily with the family AraneidaeOrb-weaver spiderThe "typical" orb-weaver spiders are the most common group of builders of spiral wheel-shaped webs often found in gardens, fields and forests...
, as well as TetragnathidaeLong-jawed orb weaverThe long-jawed orb weavers or long jawed spiders are elongated spiders with long legs and chelicerae.The spiders are orb web weavers, weaving small orb webs with an open hub and few, wide-set radii and spirals. The webs have no signal line and no retreat...
and UloboridaeHackled orb-weaverUloboridae, the cribellate orb weavers or hackled orb weavers, is a family of non-venomous spiders. Their lack of poison glands is a secondarily evolved trait. Instead, they kill their prey by crushing with over 140 metres of thread.... - Tangle webs or cobwebs, associated with the family TheridiidaeTangle web spiderTheridiidae is a large family of spiders, also known as the tangle-web spiders, cobweb spiders and comb-footed spiders. The diverse family includes over 2200 species in over 100 genera) of three-dimensional space-web-builders found throughout the world...
- Funnel webs, with associations divided into primitive and modernAraneomorph funnel-web spiderThe araneomorph funnel-web spiders of the family Agelenidae include the common grass spiders of the genus Agelenopsis, as well as the purportedly venomous European hobo spider, Tegenaria agrestis, which has been introduced into the Pacific Northwest of the United States...
- Tubular webs, which run up the bases of trees or along the ground
- Sheet webs
- Dome or tent webs
Several different types of silk
Spider silk
Spider silk is a protein fiber spun by spiders. Spiders use their silk to make webs or other structures, which function as nets to catch other animals, or as nests or cocoons for protection for their offspring...
may be used in web construction, including a "sticky
Adhesion
Adhesion is any attraction process between dissimilar molecular species that can potentially bring them in close contact. By contrast, cohesion takes place between similar molecules....
" capture silk and "fluffy" capture silk, depending on the type of spider. Webs may be in a vertical plane (most orb webs), a horizontal plane (sheet webs), or at any angle in between. It is hypothesized that these types of aerial webs co-evolved with the evolution of winged insects. As insects are spiders' main prey, it is likely that they would impose strong selectional forces on the foraging behavior of spiders. Most commonly found in the sheet-web spider families, some webs will have loose, irregular tangles of silk above them. These tangled obstacle courses serve to disorient and knock down flying insects, making them more vulnerable to being trapped on the web below. They may also help to protect the spider from predators such as birds and wasps.
Orb web construction
During the process of making an orb web, the spider will use its own body for measurements.Many webs span gaps between objects which the spider could not cross by crawling. This is done by letting out a first fine adhesive thread to drift on the faintest breeze across a gap. When it sticks to a suitable surface at the far end, the spider will carefully walk along it and strengthen it with a second thread. This process is repeated until the thread is strong enough to support the rest of the web.
After strengthening the first thread, the spider will continue to make a Y-shaped netting. The first three radials of the web are now constructed. More radials are added, making sure that the distance between each radial is small enough to cross. This means that the number of radials in a web directly depends on the size of the spider plus the size of the web.
After the radials are complete, the spider will fortify the center of the web with about five circular threads. Then a spiral of non-sticky, widely spaced threads is made for the spider to easily move around its own web during construction, working from the inside out. Then, beginning from the outside in, the spider will methodically replace this spiral with another, more closely spaced one of adhesive threads. It will utilize the initial radiating lines as well as the non-sticky spirals as guide lines. The spaces between each spiral will be directly proportional to the distance from the tip of its back legs to its spinners. This is one way the spider will use its own body as a measuring/spacing device. While the sticky spirals are formed, the non-adhesive spirals are removed as there is no need for them anymore.
The spider, after spinning its web, will then wait on or near the web for a prey animal to become trapped. The spider senses the impact and struggle of a prey animal by vibrations transmitted through the web. A spider positioned in the middle of the web makes for a highly visible prey for birds and other predators, even without web decorations
Web decorations
A web decoration or stabilimentum is a conspicuous silk structure included in the webs of some species of orb-web spider...
. Many day-hunting orb-web spinners reduce this risk by hiding at the edge of the web with one foot on a signal line from the hub or by appearing to be inedible or unappetizing.
Spiders do not usually adhere to their own webs, because they are able to spin both sticky and non-sticky types of silk, and are careful to travel across only non-sticky portions of the web. However, they are not immune to their own glue. Some of the strands of the web are sticky, and others are not. For example, if a spider has chosen to wait along the outer edges of its web, it may spin a non-sticky prey or signal line to the web hub to monitor web movement.
Uses
Some species of spiders do not use webs for capturing prey directly, instead pouncing from concealment (e.g. trapdoor spiderTrapdoor spider
Trapdoor spiders are medium-sized mygalomorph spiders that construct burrows with a cork-like trapdoor made of soil, vegetation and silk. Some similar species are also called trapdoor spiders, such as the Liphistiidae, Barychelidae, Cyrtaucheniidae and some Idiopidae and Nemesiidae...
s) or running them down in open chase (e.g. wolf spider
Wolf spider
Wolf spiders are members of the family Lycosidae, from the Ancient Greek word "" meaning "wolf". They are robust and agile hunters with good eyesight. They live mostly solitary lives and hunt alone. Some are opportunistic hunters pouncing upon prey as they find it or even chasing it over short...
s). The net-casting spider
Deinopidae
The spider family Deinopidae consists of stick-like elongate spiders that build unusual webs that they suspend between the front legs. When prey approaches, the spider will stretch the net to two or three times its relaxed size and propel itself onto the prey, entangling it in the web...
balances the two methods of running and web spinning in its feeding habits. This spider weaves a small net which it attaches to its front legs. It then lurks in wait for potential prey and, when such prey arrives, lunges forward to wrap its victim in the net, bite and paralyze it. Hence, this spider expends less energy catching prey than a primitive hunter such as the Wolf spider. It also avoids the energy loss of weaving a large orb web.
Some spiders manage to use the signaling-snare technique of a web without spinning a web at all. Several types of water-dwelling spiders will rest their feet on the water's surface in much the same manner as an orb-web user. When an insect falls onto the water and is ensnared by surface tension
Surface tension
Surface tension is a property of the surface of a liquid that allows it to resist an external force. It is revealed, for example, in floating of some objects on the surface of water, even though they are denser than water, and in the ability of some insects to run on the water surface...
, the spider can detect the vibrations and run out to capture the prey.
In traditional European medicine, cobwebs are used on wounds and cuts and seem to help healing and reduce bleeding.
Cobweb paintings, which began during the 16th century in a remote valley of the Austrian Tyrolean Alps, were created on fabrics consisting of layered and wound cobwebs, stretched over cardboard to make a mat, and strengthened by brushing with milk diluted in water. A small brush was then used to apply watercolor to the cobwebs, or custom tools to create engravings. Fewer than a hundred cobweb paintings survive today, most of which are held in private collections.
It is common for webs to be about 20 times the size of the spider building it. Spider webs are rich in vitamin K, which can be effective in clotting blood. Webs were used several hundred years ago as gauze pads to stop an injured person's bleeding.
Optics
Recently, researchers have used spider web fibers (silk threads) to induce minute disturbances into propagating N-slit interferometric signalsN-Slit interferometer
The N-slit interferometer is an extension of the double-slit interferometer also known as Young's double-slit interferometer. One of the first known uses of N-slit arrays in optics was illustrated by Newton...
, used in optical communications. These optical disturbances are detected in the form of diffraction patterns.
Adhesive properties
The stickiness of spiders' webs is courtesy of droplets of glue suspended on the silk threads. This glue is multifunctional – that is, its behaviour depends on how quickly something touching it attempts to withdraw. At high velocities, they function as an elastic solid, resembling rubber; at lower velocities, they simply act as a sticky glue. This allows them to retain a grip on attached food particles.Communal spider webs
Lake Tawakoni State Park
Lake Tawakoni State Park is a state park in Wills Point, Texas, in the United States.-Key events:The park came to media attention in 2007, because of a giant communal spider web on the premises of the park....
in Texas
Texas
Texas is the second largest U.S. state by both area and population, and the largest state by area in the contiguous United States.The name, based on the Caddo word "Tejas" meaning "friends" or "allies", was applied by the Spanish to the Caddo themselves and to the region of their settlement in...
, measured 200 yards (182.9 m) across. Entomologists believe it may be the result of social cobweb spider
Tangle web spider
Theridiidae is a large family of spiders, also known as the tangle-web spiders, cobweb spiders and comb-footed spiders. The diverse family includes over 2200 species in over 100 genera) of three-dimensional space-web-builders found throughout the world...
s or of spiders building webs to spread out from one another.
There is no consensus on how common this occurrence is.
Outside influences
Administering certain drugs to spiders has an effect on the structure of the webs they build. It has been proposed by some that this could be used as a method of documenting and measuring the toxicity of various substances.Low gravity
It has been observed that being in Earth's orbit has an effect on the structure of spider webs in space.Spider webs were spun in low earth orbit
Low Earth orbit
A low Earth orbit is generally defined as an orbit within the locus extending from the Earth’s surface up to an altitude of 2,000 km...
in 1973 aboard Skylab
Skylab
Skylab was a space station launched and operated by NASA, the space agency of the United States. Skylab orbited the Earth from 1973 to 1979, and included a workshop, a solar observatory, and other systems. It was launched unmanned by a modified Saturn V rocket, with a mass of...
, involving two female European garden spider
European garden spider
The European garden spider, diadem spider, cross spider, or cross orbweaver is a very common and well-known orb-weaver spider in Europe and parts of North America, in a range extending from New England and the Southeast to California and the northwestern United States and adjacent parts of...
s (cross spiders) called Arabella and Anita, as part of an experiment on the Skylab 3
Skylab 3
Skylab 3 was the second manned mission to Skylab. The Skylab 3 mission started July 28, 1973, with the launch of three astronauts on the Saturn IB rocket, and lasted 59 days, 11 hours and 9 minutes...
mission. The aim of the experiment was to test whether the two spiders would spin webs in space, and, if so, whether these webs would be the same as those that spiders produced on Earth. The experiment was a student project of Judy Miles of Lexington, Massachusetts
Lexington, Massachusetts
Lexington is a town in Middlesex County, Massachusetts, United States. The population was 31,399 at the 2010 census. This town is famous for being the site of the first shot of the American Revolution, in the Battle of Lexington on April 19, 1775.- History :...
.
After the launch on July 28, 1973, and entering Skylab, the spiders were released by astronaut
Astronaut
An astronaut or cosmonaut is a person trained by a human spaceflight program to command, pilot, or serve as a crew member of a spacecraft....
Owen Garriott into a box that resembled a window frame. The spiders proceeded to construct their web while a camera took photographs and examined the spiders' behavior in a zero-gravity
Weightlessness
Weightlessness is the condition that exists for an object or person when they experience little or no acceleration except the acceleration that defines their inertial trajectory, or the trajectory of pure free-fall...
environment. Both spiders took a long time to adapt to their weightless existence. However, after a day, Arabella spun the first web in the experimental cage, although it was initially incomplete.
Dehydration
In physiology and medicine, dehydration is defined as the excessive loss of body fluid. It is literally the removal of water from an object; however, in physiological terms, it entails a deficiency of fluid within an organism...
.
When scientists were given the opportunity to study the webs, they discovered that the space webs were finer than normal Earth webs, and although the patterns of the web were not totally dissimilar, variations were spotted, and there was a definite difference in the characteristics of the web. Additionally, while the webs were finer overall, the space web had variations in thickness in places: some places were slightly thinner, and others slightly thicker. This was unusual, because Earth webs have been observed to have uniform thickness.
External links
- Spiders on drugs The effects of drugs on spider web building
- More spiders on drugs More pictures of webs constructed by spiders under the influence of varied drugs
- Web construction in Araneus diadematus Movies of the web construction in the cross spider Araneus diadematus
- Oldest known spider web A 110 million-year-old web preserved in amber
- Spider Webs Vast spider web covering several trees at Lake Tawakoni State Park, Texas, in August 2007
- Spider Web Pictures Checkout some collections of the most beautiful spider web pictures.