The Caerostris darwini is a small spider, native to the jungles of Madagascar. On the outside it doesn’t appear to be in any way extraordinary – the female is about 2 centimeters in size and like many spider species its male counterpart is significantly smaller. They are black in color, covered with small white hairs which form a pattern, designed to camouflage them with the surrounding tree bark. Hence their more common name – the Darwin’s bark spider They are also named after the famous biologist Charles Darwin, as they were officially discovered on the 150th anniversary of his “On the Origin of Species”.
But despite their all too ordinary appearance, they are in fact quite remarkable. Today they are known for building the biggest spired webs in the world. A single one can cover an area of 2.8 square meters and have lines as long as 25 meters. They build their webs suspended in mid air directly above a lake or a river and attempt to catch their prey, as it’s flying over the water. This enormous structure starts off as a single line, attached to a tree on one bank of the river. The spider then crosses over, carried by air currents, thus creating a bridge. From here on it begins spiraling around it, creating an orb up to three meters in diameter.
Constructing such a huge structure puts it under enormous stress, which is additionally magnified by the struggles of the captured creatures. The individual strands can absorb massive amounts of kinetic energy, on average around 350 megajoules per cubic meter, but some can reach the amazing 520 MJ/m3. This makes them not only twice harder than any other spider silk previously known, but also the toughest biological material ever studied. The sild is in fact so strong, that it is ten times tougher than Kevlar. Such extensive nets provide the spider with rich sources of food, with scientists stating to have witnessed dozens of insects captured at a time. And although they haven’t jet seen them capturing anything larger, they believe that it is entirely possible.
Although the Darwin’s barks spider has the largest single web in the world, other species are known to work together and cover much larger areas. Known as spider blankets, such instances have happened all over the world, sometimes covering whole fields or cities. For example, the biggest ever recorded in Australia was in Esperence in 1999 and covered the ground for more than 80 kilometers.