Ever wondered why flies are attracted to beer? Entomologists have, and offer an explanation. They report that flies sense glycerol that yeasts make during fermentation. Specifically, they found that Gr64e, a receptor associated with neurons located in the fly’s mouth-parts, is instrumental in signaling a good taste for beer. Once a fly has settled on beer, Gr64e detects glycerol and transmits this information to the fly’s neurons, thus influencing the fly’s behavior.