Female Fly Reproductive Tract (IMAGE) Duke University Caption The female fly's reproductive tract is lined with neurons (green) that detect stretching. When they sense the passage of an egg (yellow), they signal the fly to start searching for a good place to lay eggs. Credit Bin Gou, Duke University 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.