Spinneret

This article is about the spider or insect organ. For other uses, see Spinneret (disambiguation).

The spinnerets of an Australian garden orb weaver spider.

A spinneret is a silk-spinning organ of a spider or the larva of an insect. Some adult insects also have spinnerets, such as those borne on the forelegs of Embioptera. Spinnerets are 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 can move both independently and in concert.

Most spinnerets are not simple structures with a single orifice producing a single thread, but complex structures of many microscopic spigots, each producing one filament. This produces the necessary orientation of the protein molecules, without which the silk would be weak and useless. It also permits spiders to combine multiple filaments in different ways to produce many kinds of silk for various purposes.

Various species of spiders use silk extruded from spinnerets to build webs, to transfer sperm, to entrap insects by wrapping it around them, to make egg-cases, to manipulate static electricity in the air and fly (ballooning), etc.

Some insect larvae (including silkworms) extrude silk to make a protective cocoon for their metamorphosis. The insects known as web spinners weave silken galleries for protection from predators and the elements while foraging and breeding.

Evolution

Observations suggesting that there might be silk-producing organs on the feet of the zebra tarantula (Aphonopelma seemanni) led to questions about the origins of spinnerets. It was hypothesised that spinnerets in spiders were originally used as climbing aids on the feet and evolved and were used for webmaking at a later time.

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  The compact spinnerets of Argiope bruennichi; placed ventrally below the posterior.
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  A barn spider encases her prey in silk emanating from her spinneret seen in the foreground.
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  Ventral aspect of spinnerets of spider species with unusually long spinnerets.

External links

• Electron microscope image of spider spinnerets