Silk - the spider's success story
Funnel-web and Trapdoor Spiders - four spinnerets with hair-like spigots.
Photo: © J Thompson.
Cribellate web-builders - six spinnerets with different types of spigots and a specialised spinning organ called the cribellum (below).
Non-cribellate web builders and hunters - six spinnerets with different types of spigots. Photo: S Lindsay © Australian Museum.
Cribellum - a flat spinning plate covered with hundreds of tiny spigots. Together these spigots produce a multi-stranded silk, called cribellate or 'woolly' silk. Photo: S Lindsay © Australian Museum.
Spiders use silk for many purposes - to protect their young, catch food, make homes and move around. They are the only animals which use silk in almost every part of their daily lives.
The original spiders, represented today by the primitive, segmented, mesothelid spiders, had eight pairs of silk spinning organs or spinnerets placed under the middle of the abdomen (Mesothelae). In mygalomorph and araneomorph spiders the spinnerets have moved to the end of the abdomen (Opisthothelae). In these spiders the anterior median spinnerets (AMS) are either no longer present or remain in some araneomorph spiders as a modified spinning structure called the cribellum. Mygalomorph spiders have four or six spinnerets, compared to six in most araneomorphs.
The paired spinnerets have one to three segments. They are highly manoeuvrable for silk spinning and may be quite short or relatively long (as long as the abdomen in some mygalomorph spiders). The end segment of each spinneret has many spigots - hollow, hair-like silk outlets connected to particular paired silk glands within the abdomen. Each gland opens on the spinnerets either via one or two spigots (ampullate glands), several spigots (cylindrical glands), or many spigots (pyriform and aciniform glands). In addition, the cylindrical and aciniform glands open onto two spinnerets.
As well as the spinnerets, many male spiders have an area of hair-like spigots near the gonopore (epiandrous spigots) that produce silk for the spider's sperm web.
Find out more:
- Silk factories - the spider's silk glands
- Silk structure
- How silk works - the orb web
- Making a dragline
- Why don't spiders stick to their webs?
- The specialised catching silks
- Types of webs
