Silk Craft in Nature – Spider Silk
The spooky spider web is the signature Halloween decoration. To the spiders, however, the web is actually a matter of life and death! There is an amazing diversity of spider webs with regard to the materials, weaving methods and uses. Let's look closer at the magical creativity of nature!
The strength of spider silk has inspired considerable development in material science of the human world. Apart from its strength, there are other unique qualities. Scientists have studied the properties of different spider silks that fulfil the various needs of spiders. These include differences in thickness and stickiness – for example, major ampullate silk is non-stick but can carry a load; flagelliform silk has high ductility and malleability; and pyriform silk is highly sticky. The silk threads are made up of various protein fibres that are secreted from seven different glands, and are extruded from the spinneret, the organ at the end of the spider's abdomen.
Weaving Patterns
Spider webs are the most important hunting tool for “sit-and-wait” spiders. Multiple patterns of spider webs are built in response to different environments and prey types. Orb webs may be the most commonly seen. The radar-screen-like web is created almost vertically between tree branches or at corners of walls to catch flying prey.
Members of the family Agelenidae build funnel webs, mostly close to the ground among grasses or on rocks. They are fast sprinters which usually hide at the bottom of the funnel, and swiftly catch the insect prey that falls on the web and retreat to the bottom to feed on it. Members of the Deinopidae family are net-casting spiders. They stretch their webs across their legs, and cast the net towards approaching prey to entangle it.
Beyond Preying
All spiders have spinnerets that make silk, yet not all can weave. Hunting is not the only use of the silk threads. Female spiders can produce egg sacs with the toughest tubuliform silk to protect the eggs inside. Many small spiders can weave a “ballooning” thread that carries them aloft on rising air; some may even “fly” in the air as high as five kilometres above sea level!
Another special species is the Diving Bell Spider, Argyroneta aquatica. As its name suggests, this spider is able to dive for a long time in water to hunt, by creating a diving bell around its abdomen carrying air within the space. How amazing!