spider silk

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 move independently and in concert.

   http://en.wikipedia.org/wiki/Spider_silk