Flies Settle on Beer (IMAGE) University of California - Riverside Caption Flies are attracted to beer because they detect glycerol, a sweet-tasting compound that yeasts make during fermentation. Credit Dahanukar lab, UC Riverside. 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.