Swarming flies (IMAGE) University of Gothenburg Caption When dance flies mate, females make themselves more attractive by swallowing air and laying their hairy legs along their bodies to look like they are full of eggs. New research shows that the males have developed better eyesight, probably to detect the deception. Credit John Alcock Usage Restrictions None License Original 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.