Chordotonal organs are stretch receptor organs found only in insects and crustaceans.[1][2][3] They are located at most joints[2] and are made up of clusters of scolopidia that either directly or indirectly connect two joints and sense their movements relative to one another. They can have both extero- and proprioceptive functions, for example sensing auditory stimuli or leg movement.[4] The word was coined by Vitus Graber in 1882, though he interpreted them as being stretched between two points like a string, sensing vibrations through resonance.[5]