Science Snippet: Flying Spiders

Biologists can go to great lengths to test their theories. For example, Prof. Steve Yanoviak of the University of Louisville wondered whether spiders can fly, and he set out to answer the question by throwing various species of spiders out of a tree and watching them as they struggled to counteract gravity. Most species failed and plummeted to the ground. However, spiders of the genus Selenops managed to steer themselves to safety on either the tree from which they were dropped or to a neighboring tree. Eureka! Yanoviak had made a scientific discovery. To test his discovery, he collected 59 specimens of the species, covered them with orange powder to make them easy to see as they fell, and dropped them from treetops. He videotaped their falls and found that all the spiders except one managed to steer themselves to a tree. They didn’t fly but they glided, using their forelegs as rudders and their outstretched legs as parachutes. Selenops was the only spider to achieve this feat. Now Yanoviak has another question to answer – why? (Yanoviak, Munk, and Dudley, J. of the Royal Society Interface, Aug. 19, 2015; The Economist, Aug. 22, 2015; a video of gliding spiders can be seen at: economist.com/spiders)