Orb web

A spider web, spiderweb, spider's web, or cobweb (from the archaic word , meaning "spider") is a device created by a spider out of proteinaceous spider silk extruded from its spinnerets, generally meant to catch its prey.

Spider webs have existed for at least 100 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. "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. However, "cobweb" is used to describe the tangled three-dimensional web of some spiders of the theridiidae family. While this large family is also known as the tangle-web spiders, cobweb spiders and comb-footed spiders, they actually have a huge range of web architectures.

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 that are familiar 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.

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Wikipedia