Mayflies in a Pennsylvania Stream (IMAGE) Utah State University Caption According to a study conducted by scientists from Utah State University and the US Environmental Protection Agency, the mayfly Epeorus pleuralis, one of the many hundreds of species of stream insects whose frequencies of occurrence has declined relative to historical conditions. Credit David Funk, Stroud Water Resources Center, Pennsylvania Usage Restrictions Please credit David Funk, Stroud Water Resources Center, Pennsylvania 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.