Fly pheromones can say yes and no

The same chemicals that attract can also maintain the species barrier

View a video of flies showing unusual courtship behavior.

SWEET SCENT OF FLIES The cells in Drosophila melanogaster that produce pheromones are located in the abdomen. Here, the cells are marked by a green fluorescent protein. Jean-Christophe Billeter

Honey’s sweet smell attracts more flies than does vinegar’s sour odor, but the ultimate fruit-fly magnet is eau de nothing.