The Amazing Spider Web!!!
A spider web, or cobweb (from the obsolete word coppe, meaning “spider”) is a device built by a spider out of proteinaceous spider silk extruded from its spinnerets.
Spider webs have existed for at least 141 million years. Insects 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. “Spider web” is typically used to refer to a web that is apparently still in use (i.e. clean), whereas “cobweb” refers to abandoned (i.e. dusty) webs.
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.
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:
- Spiral orb webs, associated primarily with the family Araneidae, as well as Tetragnathidae and Uloboridae
- Tangle webs or cobwebs, associated with the family Theridiidae
- Funnel webs, with associations divided into primitive and modern
- Tubular webs, which run up the bases of trees or along the ground
- Sheet webs
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.
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.
Administering certain drugs to spiders affects 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. Visit the following link for more information.