Researchers studying tobacco hornworm caterpillars have found evidence that the insects can "hear" despite lacking ears or the tympanal membranes typically associated with hearing in other creatures. Understanding how these caterpillars detect approaching predators, such as wasps, could resolve a long-standing puzzle in biology and may also inspire cheaper, more sensitive microphone technology inspired by their sensory hairs.

To test this, the team placed caterpillars in an anechoic chamber, an extremely quiet, vibration-isolated room, and exposed them to both direct vibrations and airborne sound over the course of a year, using an accelerometer to measure the resulting movements. They established a threshold below which the caterpillars stopped reacting to vibrations, but found the animals continued responding to airborne sound even when it fell beneath that threshold, indicating they were genuinely hearing rather than merely feeling vibrations. This pointed the researchers towards tiny, highly sensitive hairs on the caterpillars' bodies as the likely mechanism behind their unusual sense of hearing.