Hessian Flies on a Piece of Wheat (IMAGE) Purdue University Caption These are two Hessian flies on a piece of wheat. Credit Purdue Agricultural Communication photo/Tom Campbell 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.