SALT LAKE CITY March 1 2010 --- Like silkworm moths(蚕蛾) butterflies and spiders caddisfly larvae(石蛾幼虫) spin silk but they do so underwater instead of on dry land. Now University of Utah researchers have discovered why the fly’s silk is sticky when wet and how that may make it valuable as an adhesive tape(黏胶带) during an operation.“Silk from caddisfly larvae may be useful some day as a medical adhesive for sticking wet tissues ” says Russell Stewart an associate professor of bioengineering and principal author of a new study of the fly silk’s chemical and structural properties. “I picture it as sort of a wet Band-Aid maybe used inside in operations --- like using a piece of tape to close a cut ” he adds. “Gluing things together underwater is not easy. Have you ever tried to put a Band-Aid on in the shower? This insect has been doing this for 150 million to 200 million years.”There are thousands of caddisfly species worldwide. Some species spend their larval stages developing underwater and build an inch-long tube-shaped case or shelter around themselves using sticky silk and grains of rock or sand. Other species use silk small sticks and pieces of leaves. Each larva has a head and four legs that stick out from the tube.The larval case gets wider as the larva grows.A caddisfly larva eventually pupates(化蛹)as it develops into an adult fly and then hatches.Caddisflies now live around the world in waters ranging from fast streams to quiet low lying wet land. The caddisflies’adaptation to diverse habitats is largely due to the inventive use by their larva of underwater silk to build plex structures for protection and food gathering.Caddisflies fall into two groups. Some build their case and then drag it along with them underwater as they search for food. Some build a shelter glued to a rock with a silk net to catch passing food.59.According to Russel Stewart caddisfly larvae ______. A. can spin silk underwater or on dry landB.are worth researchingC.are quite different from butterflies and spidersD.have been widely used in the medical field60.The author mentioned “Band-Aid” in the passge to show ______.A.Band-Aids are very useful B. Band-Aids can’t be used in operations.C. it’s not easy for caddisfly larvae to live underwaterD. silk from caddisfly larvae has an advantage over BandAids61. The underlined word “it” in the last paragraph probably refers to ______. A. the silk B. the shelter C. the food D. the rock62. The passage is most probably a ______.A. science fiction novel B. science news reportC. biography of researchers D. social affairs report
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【答案】 BDBB