Spiders produce a variety of silks that can be classified into 7 distinct types: Major Ampullate, Minor Ampullate, Pyriform, Aciniform, Flagelliform, Tubuliform and Viscous Aggregate. The silks are produced in separate glands for special purposes. Major Ampullate silk is used in the radii (spokes) of orb web spiders and as a safety line in other spiders. The Minor Ampullate silk is used for prey wrapping.
Flagelliform silk is used in the axial strands of webs. Compared to the Major Ampullate silk, it is not as strong but is more extensible. When prey flies into the web, the strands stretch to gently slow the speed and allow the prey to stick to the web instead of bouncing. To facilitate prey capture, the axial strands may be coated with gooey Viscous Aggregate which provide greater contact area with the prey.
Pyriform silk is used to attach and anchor webs to objects and can glue silk strands together. Aciniform silk is used to construct egg sacs and wrap prey. Its considerable stiffness us suited to these uses. The outer coating of the egg sac is typically Tubuliform silk.
Silk is a multipurpose material. Different silk proteins can give silk unique properties adapted to the needs of the spider. Studies of silks are useful for producing biomimetic materials.