To many web-building spiders, most of【C1】______ are nearly blind, the web is their essential window【C2】______ the world., their means of communicating,【C3】______ prey, meeting mates and protecting themselves. A web-building spider【C4】______ its web is like a man marooned on an island of solid rock, totally out of touch and destined to starve to death. So【C5】______ is the web to an orb-web spider's survival that the animal will continue to construct new webs daily【C6】______ it is being starved. For 16 days the【C7】______ spider builds completely normal webs. Then, as the animal gets scrawnier, it constructs a wider-meshed web using【C8】______ strands. Such webs would only trap larger prey, which is more【C9】______ from the perspective of a starving spider. The spider【C10】______ energy by recycling web protein. It simply eats its own web each evening and re-uses it to manufacture【C11】______ silk. In studies with radioactively labeled materials, it【C12】______ that 95 percent of web protein reappeared in【C13】______ web. Most of the energy needed for web-building is used in walking over the strands as they are laid down. Scientists are【C14】______ by the adaptability of the spider's highly preprogrammed brain, which is larger【C15】______ its size than the brain of any other invertebrate. If web-building is interrupted, or if some of the【C16】 ______ strands are destroyed, the spider【C17】______ retraces its steps to see where the web is【C18】______ and then finishes building a【C19】______ web. One spider will even finish building the incomplete web of【C20】______ . 【C1】