A spider on the world wide web
My travels and guiding have prevented me from writing a newsletter for quite a few weeks so I feel that I owe it to you to write a special piece this week. On my most recent safari we spent a few days at Umlani Bush Camp and after the massive March rains the bush was still very lush. Most noticeable was the enormous numbers of Banded-Legged Golden Orb-Web Spiders (Nephila senegalensis) on their giant webs. They were present in such large numbers that it was impossible to avoid damaging some webs while out on foot. The heavy late rains have clearly favoured them and as the dry cold season sets-in they will be less evident. I did manage to get a few great photos of these beautiful spiders and here is my favourite . In this photo you can also see a tiny kleptoparasitic dewdrop spider (genus Argyrodes). These small spiders live on the web of the host Golden Orb-Web Spider. It seems that they eat scraps left-over by the host, in which case they would not be parasites and the relationship would appear to be mutually beneficial.
The genus name “Nephila” comes from ancient Greek and means “fond of spinning”, and looking around in The Timbavati these spiders certainly are fond of spinning. Their webs are golden yellow in colour and extremely strong. In fact they are so strong that there are several records of birds (as large as a laughing doves) being caught in these webs. Weight for weight, spider silk is tougher than Kevlar (toughness is a combination of tensile strength and ductility). If spider silk could be produced artificially it would have many practical applications in medicine, safety material and garment manufacture. In spite of the fact that it has the same tensile strength as steel, spider silk is so light that a strand wrapped around the earth at the equator would weigh less than 500 grams.
The quest to create garments from spider silk goes all the way back to 1710, when Francois Xavier Bon de Saint Hilaire produced socks and gloves from spider silk obtained by boiling spider cocoons. Almost a hundred years later a Jesuit priest by the name of Raimondo Maria de Termeyer discovered that threads obtained from the spider itself were stronger than those from the cocoons. This encouraged a short-lived industry using an apparatus to extract silk thread from live spiders. In 2004 two men embarked upon a project to create a garment made from Golden Orb-Web Silk. It subsequently took them & 82 assistants four years to create a larger cape (3.2m * 1.2m) using silk obtained from 1.2 million female spiders.
The webs of Golden Orb-Web Spiders have been used by fishermen to catch small fish. Spider silk appears to have antiseptic properties and historically has been used as a dressing on wounds. More recently Golden Orb-web spider silk has been investigated medicinally and successfully used as a scaffold to assist nerve regeneration in mammals.
So instead of screaming next time you are in the bush and see these spiders, rather marvel at the miracle of evolution and ponder the potential benefits that humanity will derive from these fascinating creatures.