No Ears, No Problem: How Microscopic Hairs Turn Caterpillars Into Airborne Sound Detectors

National Geographic reveals how caterpillars use microscopic hairs to detect sounds, helping them dodge predators and inspiring new microphone technology.

By: AXL Media

Published: Feb 24, 2026, 8:32 AM EST

Source: The information in this article was sourced from National Geographic

The Accidental Discovery of Caterpillar Audition

The realization that caterpillars could perceive airborne sound began not with a formal experiment, but with a series of startled insects in a biology lab. Associate Professor Carol Miles noticed that whenever she spoke near her collection of tobacco hornworm caterpillars, the jade-colored larvae would jump or twitch as if frightened. According to National Geographic, her colleagues jokingly told her to "shut up" because she was scaring the bugs, prompting a decade-long investigation into how an organism without eardrums could respond so acutely to the human voice.

Differentiating Airborne Sound from Surface Vibration

For years, scientists assumed caterpillars only "heard" by feeling mechanical vibrations through the leaves and stems they inhabit. To isolate the true source of their sensitivity, researchers tested the insects inside an anechoic chamber—one of the world's quietest rooms—where airborne sound and surface vibrations can be delivered independently. According to the study published in the journal of the Acoustical Society of America, the caterpillars were 10 to 100 times more responsive to airborne sound than to the vibrations beneath their feet, confirming a genuine sense of hearing.

Microscopic Hairs as Biological Sound Sensors

Without eardrums, caterpillars rely on a forest of microscopic hairs, known as trichoid sensilla, covering their abdomen and thorax. These hairs are extremely light and sensitive to "acoustic particle velocity," meaning they move in response to the physical displacement of air molecules caused by sound waves. According to National Geographic, when researchers carefully removed these fine hairs, the caterpillars' response to sound dropped sharply. This confirms that the hairs function as biological sensors, converting air movement into electrical signals for the caterpillar's nervous system.