There is an incredibly rich diversity of specializations in the cuticular surface of crustaceans. Some of these structures are innervated by sensory neurons and are called sensilla. Sensilla may be innervated by mechanoreceptive neurons, by chemoreceptive neurons, or by both types of neurons. Although many types of sensilla from many groups of crustaceans have been identified and morphologically described, our knowledge of physiological response properties of neurons within morphologically identified sensilla is much more limited and comes almost exclusively from the larger decapod crustaceans. Nonetheless, these physiological studies have given us important information as to how these mechanosensors and chemosensors determine the qualitative, quantitative, directional, and temporal nature of mechanical and chemical stimuli — the type of information necessary for the animal possessing these sensors to survive and prosper.