These Butterflies Can Hear With Their Wings

For a century, nobody knew why Satyrini butterflies had inflated veins on their forewings. Turns out the structures are hearing aids.
Common wood nymph. ​Image: D. Gordon, G. Robertson
Common wood nymph. Image: D. Gordon, G. Robertson

Watch what you say around butterflies, because some of them are eavesdropping on you with their wings. That’s the word from new research published in Biology Letters that identified hearing organs embedded in the wing veins of common wood-nymph butterflies (Cercyonis pegala).

While it is already wellknown that some butterfly species have small ear-like cavities at the base of their wings, these hearing veins located on the wings are a totally new discovery.


“This study resolves a century old conundrum concerning the function of inflated wing veins in butterflies,” the authors concluded. “We show that they function in hearing.”

Inflated wing veins are a distinguishing feature of Satyrini butterflies, a diverse family of 2,500 species with worldwide range. They are located on each forewing, the upper-level set of wings, and appear to be beefed-up compared to the more common, scaffold-like veins used to maintain structure on both the hindwings and forewings.

Neuroethologist Jayne Yack and her team at Carleton University’s Yack Lab, a laboratory focused on biological sensory systems, noticed the inflated veins were close to ear cavities. That tipped Yack and her team off that the veins could have an acoustic function.

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Yack enlisted the help of Natasha Mhatre, an expert in insect acoustic communication at the University of Toronto, who examined the responses of 30 common wood-nymph butterflies to different low-frequency sounds in the same general range as human voices.

Using a technique called laser vibrometry, which involves imaging the insect ears with laser light, Mhatre monitored the response of the butterflies to the sounds. She discovered that the veins were part of a larger hearing apparatus that redirects sound waves to the ear drums, a conclusion further validated after small incisions in the veins reduced hearing sensitivity in the butterflies.

The discovery of an entirely new function of a long-observed wing feature shows how much there is still to learn about how insects experience the world. “Hearing in butterflies is widespread, but at present little is known about the function and evolution of these sensory organs,” Yack and her colleagues said in the study.

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