spinnerets

Spinnerets are paired terminal appendages on the posterior abdomen of spiders and other silk-producing arachnids. They act as the external exit points for silk, which is produced inside the body and then drawn out as a filament. In most spiders there are six spinnerets arranged in three pairs (anterior, median, and posterior), though the exact count and arrangement can vary by species.

Each spinneret bears multiple microscopic openings connected to specialized silk glands within the abdomen. Silk is produced as a protein dope in these glands and is extruded through ducts to the spinneret openings, where it solidifies into fiber. Different glands produce different silks: major ampullate (strong dragline), minor ampullate, aciniform (tethering and wrapping), piriform (attachment threads), and tubuliform (egg sacs). The combination and control of these silks enable web construction, prey capture, nest building, and egg protection.

Spinnerets can move independently, allowing spiders to blend silks from several glands as needed. The arrangement and function of spinnerets vary among species, reflecting ecological differences and the diversity of silk-based behaviors. The study of spinnerets and spider silk proteins (spidroins) informs biomimetic materials research and has inspired advances in fiber technology and synthetic silk production.