SALT LAKE CITY, March 1, 2010 --- Like silkworm moths , butterflies and spiders, caddisfly larvae  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  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 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 complex 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. The passage is most probably a   _  .
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