Partitioning continuously varying stimuli into categories is a fundamental problem of perception. One solution to this problem, categorical perception, is known primarily from human speech, but also occurs in other modalities and in some mammals and birds. Categorical perception was tested in crickets by using two paradigms of human psychophysics, labeling and habituation-dishabituation. The results show that crickets divide sound frequency categorically between attractive (<16 kilohertz) and repulsive (>16 kilohertz) sounds. There is sharp discrimination between these categories but no discrimination between different frequencies of ultrasound. This demonstration of categorical perception in an invertebrate suggests that categorical perception may be a basic and widespread feature of sensory systems, from humans to invertebrates.