Caterpillar twitches in an ultraquiet chamber are helping biologists understand how these insects hear without ears

Scientists studying tobacco hornworm caterpillars have found evidence the insects detect approaching predators, such as wasps, despite lacking ears, likely through supersensitive hairs on their bodies. Working inside an anechoic chamber that isolates sound and vibration, researchers exposed caterpillars to varying vibration and airborne sound intensities and measured reactions like jumping, twitching, and shuddering using an accelerometer.

The caterpillars kept reacting to airborne sound even below the threshold at which they responded to direct vibration, suggesting true hearing rather than vibration-sensing alone. When researchers removed specific hairs, defensive reactions to sound dropped sharply, pointing to those hairs as the likely hearing mechanism — a finding the team hopes could eventually inspire new microphone designs.

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