Acetic acid vapour as a resource: threshold differences among three Drosophila species.

Acetic acid vapour is utilized as an energy source up to a threshold where it becomes a stress in 3 Drosophila species. The threshold ranking is D. melanogaster much greater than D. simulans greater than D. immigrans, which qualitatively parallels that for ethanol. The capacity to use nutritive vapours appears to be very important in Drosophila ecology.