It is known that substrate-borne vibrations are detected by insects from multiple taxa and life stages, including adults and larvae. Therefore, in this thesis I aimed to answer the question "How do caterpillars detect vibration?". For this purpose, I made neurophysiological experiments on proleg hairs of Drepana arcuata and Trichoplusia ni caterpillars. In these experiments, two types of mechanical stimuli were applied to the proleg hair: 1) sine vibrational signals with varying frequencies and 2) single push/pull stimuli. Amplitudes of stimuli ranged from sub- to supra-threshold and stimuli were applied in multiple directions to test for sensory directionality. With this, I showed that the sensory activity of the hair can be characterized as a rapid adapting response, that it has directional sensitivity and presents some phase-locking. In conclusion, the sensory hairs here evaluated can respond to vibration, which leaves them as potential candidates for substrate-borne vibration receptors in these caterpillars.