To small insects, praying mantids probably do seem like something out of a monster movie. Mantids are some of the most impressive insect predators, regularly snaring other insects or even the occasional lizard, snake or frog.
But despite their hunting skills, mantids are ill-equipped to avoid predation themselves. Camouflage keeps some well hidden from visual hunters such as birds, but matching the color of your background won't hide you from nocturnal predators, like bats. Many bats locate their prey in total darkness by echolocation-producing ultra-high pitched calls and listening to the reflections, or echoes off objects in their environment.
Praying mantids were long thought to be deaf, but neuroscientists at Cornell and the University of Maryland discovered a single teardrop-shaped ear along the middle of praying mantis' thorax. Praying mantids don't produce sounds, and don't use sound to locate their prey, so why would they need to hear?
Because of bats! The researchers tested whether the mantids' unique ear could hear the ultrasonic cries of bats, which are too high pitched for human ears to detect. When the scientists played recordings of bat echolocation calls to free-flying mantids, the mantids abruptly stalled in the air and erratically spiraled downward, dropping out of the sky. The evasive maneuvers enable a normally slow-flying mantid to escape bat attacks in nearly eighty-percent of trials. When scientists deafened the mantids, they only escaped bat attacks thirty-four percent of the time. So ultrasonic hearing gives mantids a huge advantage.