Abstract ( Z )-4-undecenal ( Z 4-11Al) is the volatile pheromone produced by females of the vinegar fly Drosophila melanogaster . Female flies emit Z 4-11Al for species-specific communication and mate-finding. A sensory panel finds that synthetic Z 4-11Al has a characteristic flavour, which we perceive even at the small amounts produced by one female fly. Since only females produce Z 4-11Al, and not males, we can reliably distinguish between single D. melanogaster males and females, according to their scent. Females release Z 4-11Al at 2.4 ng/h and we readily sense 1 ng synthetic Z 4-11Al in a glass of wine (0.03 nmol/L), while a tenfold concentration is perceived as a loud off-flavour. This corroborates the observation that a glass of wine is spoilt by a single D. melanogaster fly falling into it, which we here show is caused by Z 4-11Al. The biological role of Z 4-11Al or structurally related aldehydes in humans and the basis for this semiochemical convergence remains yet unclear.