Taste and smell have a similar function: detecting chemicals from the external world. Despite this
common functionality, the two systems are designed very differently both at the level of the sensory
receptors and in the way information is mapped into the brain. While olfaction is tuned towards
detecting volatile chemicals from air, the taste system is specialized for detecting non-volatile
molecules through contact. Usually the two systems have been studied separately, under the
assumption that both systems are tuned to detect divergent and non-overlapping ensemble of
molecules. We show through electrophysiology that taste sensilla on the proboscis of Drosophila
detect airborne molecules associated with food like acetic acid, acetone and isoamyl propionate,
as well as compounds known to be aversive to the olfactory system like 1-octen-3-ol (associated
with pathogenic microbes). Behavioral tests like Y-maze assay, 4-arm olfactometer assay and
proboscis extension response show that flies deprived of their olfactory organs are capable of
showing response to acetic acid vapors. However mutant flies lacking taste sensilla (and with
olfactory organs ablated) do not respond to such vapors. This shows that the taste system has the
ability to detect some volatile compounds at close range, raising questions about whether there is
a clear separation between the olfactory and gustatory sensory space, at least in insects.