Spider Web
Spiders produce silken threads that are used for building webs, snares, draglines and cocoons.
Some other animals also produce silk at some stage in their life cycle. These species include some Lepidoptera (moths and butterflies), neuropteran (lacewings, mantidflies and antlions) and hymenoptera (bees, wasps, ants and sawflies).
Spiders produce silken threads throughout their life span, and for purposes not confined to a single stage in a life-cycle.
Spider webs are made of silk produced in so called spinning glands. There are many types of silks, however, they are all made of proteins and something called fibroins.
The silk is secreted from glands inside the spider, and is solidified to withstand the tension is it subjected to when used.
The solidification process is not fully understood, but is hypothesized that a conformational change in the silk is responsible for turning the water soluble liquid silk into an insoluble form. In silk moth this process of changing the conformation is brought about by pulling the silk.
Each thread in a web consists of something called alpha-chains and beta-pleated sheets. The sheets are stacked and embedded into a matrix of amino acids. Spiders thread is known to be very strong.
The threads water content is an important parameter for how the thread responds to forces. A dry thread breaks if stretched too much, while a thread with a high water content can withstand to be stretched to three times its normal length.
Therefore, spider webs are often constructed with a mixture of relatively dry and wet threads. Dry stiff threads are used for the basic framework, while elastic threads with higher water content are used for catching prey.
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