Spinneret

A spinneret is a spider's or insect larva's silk-spinning organ. It is 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. Different species of spiders use silk extruded from spinnerets to build webs, to entrap insects by running round them, to make egg-cases, to catch the wind and fly (ballooning), etc. Some insect larvae (including silkworms) extrude silk to make a protective cocoon for their metamorphosis.

The discovery of silk-producing organs on the feet of the zebra tarantula (Aphonopelma seemanni) has led to questions about the origins of spinnerets. It has been hypothesised that spinnerets were originally used as climbing aids on the feet and evolved and were used for webmaking at a later time.