The tropical golden orb-web spider (below)spins the world’s biggest web. It can be up to 1.5 metres (5 feet) across. The smallest, spun by midget spiders, can be less than 16 mm (0.4 inches) across. Silk strands can stretch to double their original length. A steel thread, however, will snap when it is stretched by only 8 per cent.
The orb-weaving spider, from which BioSteel is derived, makes seven different kinds of thread. The strongest, dragline silk, has a tensile strength almost as strong as steel on a volume-for-volume basis. As steel is 7.8 times denser, dragline silk is about five times stronger weight for weight. It is used for building webs and abseiling to the ground.
Other varieties of silk include minor ampullate silk, which is slightly less strong but has almost no elasticity: once stretched, it remains in the same shape, rather like toffee. Flagelliform silk, however, which is used to catch flying insects, is so elastic that it reverts to its original shape even after being stretched to more than twice its original length. The web of a common garden spider contains as much as 30 metres (100 feet) of silk, yet weighs just 0.00017ounces. A single thread of dragline silk can bear six times the weight of its maker before it snaps.
There are thought to be about 35,000 different species of spider: many uncharted species may have even stronger silks.
