Why do flies like beer? It's sweeter than you think. Entomologists say the flies sense glycerol, the sweet-tasting compound that yeasts make during fermentation.
The researchers examined the feeding preference of the common fruit fly for beer and other products of yeast fermentation, and found that a receptor - a protein that serves as a gatekeeper - called Gr64e is associated with neurons located in the fly's mouth 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, which then influences the fly's behavioral response. Flies use other receptors in their sensory organs to find food from a distance.