Gregory Courtney, Iowa State University (IMAGE) Iowa State University Caption The problem with tracking fly evolution is that every so often, a species of fly will branch into two different species, and then those two will split again, and again and so forth, said Gregory Courtney, professor of entomology. If a series of these branches occurs over a brief period of time, the result will be a rapid radiation of new flies and an evolutionary tree that may look more like a bush. Credit ISU photo by Bob Elbert Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.