Plants Smell Danger (image) Penn State Caption True fruit flies are gall-inducing insects. After a female fly's eggs hatch on the plant a large growth, or gall, appears. Credit Credit: Ian Grettenberger Usage Restrictions None 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.