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An animal's decision to accept or reject a prospective food is based only, in part, on its chemical composition. Palatability is also greatly influenced by textural features including smoothness versus grittiness, which is influenced by particle sizes. Here, we demonstrate that Drosophila melanogaster is endowed with the ability to discriminate particle sizes in food and uses this information to decide whether a food is appealing. The decision depends on a mechanically activated channel, OSCA/TMEM63, which is conserved from plants to humans. We found that tmem63 is expressed in a multidendritic neuron (md-L) in the fly tongue. Loss of tmem63 impairs the activation of md-L by mechanical stimuli and the ability to choose food based on particle size. These findings reveal the first role for this evolutionarily conserved, mechanically activated TMEM63 channel in an animal and provide an explanation of how flies can sense and behaviorally respond to the texture of food provided by particles. [Display omitted] • Flies prefer feeding on foods containing particles of a certain size • Sensation of particles in food depends on the OSCA/TMEM63 channel • TMEM63 detects particles in food through subtle deflections of taste sensilla • Mild deflections of sensilla require TMEM63 for activation of md-L neurons In humans, the size of particles in food influences palatability. Li and Montell establish that flies also evaluate the size of particles in food and use this information to assess its appeal. Flies discriminate particle sizes in food through mechanical activation of the TMEM63 channel in a multidendritic neuron (md-L) in their tongue. [ABSTRACT FROM AUTHOR]