Drosophila has 6 classes of taste receptors on its tarsi, based on response to sugar/sweet/sour/bitter. Flies walking on potential food items receive information about the quality. Using the legs to taste is more efficient than using the mouthparts would be.
Receptors on the prothoracic (front) legs differ in quality from receptors on the mouthparts and the metathoracic (middle) legs. The receptors on the mouthparts only contact the food after the information from the leg receptors have convinced the fly to begin feeding. Apparently the fly needs different information about the food it is eating than it needs to make its decision to eat. The differences in taste receptors in different locations on the fly provide a means to connect the function of the receptors with fly behavior.
Taste reception has components in common in all animals. What we learn from fruit flies can be used to better understand our own sense of taste.
Time flies like an arrow.
Fruit flies like a banana.
The Journal of Neuroscience, 21 May 2014, 34(21): 7148-7164