考研英语阅读100篇unit21.docx

TEXT ONE When honey bees began to desert their hives recently, never to return, it threw apiarists into a panic. What appeared to be perfectly healthy adult bees would flee their queen, the young and their foodstores. Instead of ransacking the empty hive, other bees would avoid it like the plague. Yet there was nothing obviously wrong. Researchers have now identified the first tangible clue in the mystery—a relatively new virus. Colony collapse disorder became widespread in America in the winter of 2006-07, when about a quarter of the nations beekeepers were affected, each losing between 30% and 90% of their winged workers. Bees are valued not so much for their honey, which is worth some $200m a year in America, but for their work in pollinating crops. This brings the economy some $15 billion a year, as apiarists move their hives to land producing fruit, vegetables and nuts. Finding exactly why colonies collapse has been taxing the minds of both federal and university scientists. There have been few bodies on which to conduct autopsies. Those adult bees that have been found dead near an abandoned hive have been riddled with almost every bee disease known to man. Now a report by Diana Cox-Foster of Pennsylvania State University and her colleagues, published in the September 6th issue of Science, points the finger at the Israeli acute paralysis virus. The lurgy in question was, the researchers suggest, imported from Australia. Because many factors could be acting together to cause bee colonies to collapse, Dr Cox-Foster and her colleagues decided to examine everything they could find within the empty hives. They collected samples from infected hives and compared them not only with samples from apparently healthy hives but also with an analysis of royal jelly—a bee secretion fed to the larvae—from China, which has not been affected by the mystery disorder. From their samples, the researchers extracted RNA—a chemical that carries and helps to decode genetic informat