Many praying mantids possess a unique cyclopean auditory system comprising a single ear located in the ventral midline of the caudal metathorax. Hearing is used primarily for bat avoidance. The 2300 species of mantids come in a broad range of shapes and sizes occupy a similarly broad range of ecological niches. We asked whether or not there was also a range of auditory capabilities and, if so, would it be possible to infer some details of the evolutionary history of the mantis ear. We studied the metathoracic anatomy of 344 genera of mantids and also defined auditory function neurophysiologically for 48 genera (66 species). This survey uncovered six anatomical and physiological patterns related to audition that provided a hypothesis for mantis ear phylogeny. We then superimposed the distribution of auditory patterns on a phylogenetic tree derived from mitochondrial and nuclear genes of >200 mantis species. The correspondence of the two trees was close, and showed that: some extant mantids are primitively earless; many species are secondarily deaf, especially in cases of auditory sexual dimorphism; the cyclopean auditory system evolved just once; other patterns apparently arose several times; the evolution of a second, serially homologous midline ear occurred late in the evolution of mantids. The molecular data allow us to derive a hypothetical time line relating the evolution of the mantis ear to the appearance of predators including bats.