Can Plants Hear Their Pollinators? #ASA188

Can Plants Hear Their Pollinators? #ASA188

Research suggests pollinator buzzing sounds lead plants to increase their nectar production.

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NEW ORLEANS, May 21, 2025 – When pollinators visit flowers, they produce a variety of characteristic sounds, from wing flapping during hovering, to landing and takeoff. However, these sounds are extremely small compared to other vibrations and acoustics of insect life, causing researchers to overlook these insects’ acoustic signals often related to wing and body buzzing.

Francesca Barbero, a professor of zoology at the University of Turin, and her collaborators — an interdisciplinary mix of entomologists, sound engineers, and plant physiologists from Spain and Australia — studied these signals to develop noninvasive and efficient methods for monitoring pollinator communities and their influences on plant biology and ecology.

Barbero will present her findings and their impacts on Wednesday, May 21, at 9 a.m. CT as part of the joint 188th Meeting of the Acoustical Society of America and 25th International Congress on Acoustics, running May 18-23.

A photo of the recording device, the model snapdragon plant (A. litigiousum), and the approaching bee (R. sticticum). Credit: Vibrant Lab

“Plant-pollinator coevolution has been studied primarily by assessing the production and perception of visual and olfactory cues, even though there is growing evidence that both insects and plants can sense and produce, or transmit, vibroacoustic signals,” said Barbero.

Barbero and her collaborators played recordings near growing snapdragons of the buzzing sounds produced by a Rhodanthidium sticticum bee (sometimes called a snail-shell bee) to monitor the flowers’ reactions. The researchers found that the sounds of bees, which are efficient snapdragon pollinators, led the snapdragons to increase their sugar and nectar volume, and even alter their gene expression that governs sugar transport and nectar production.

The flowers’ response may be a survival and coevolution strategy, especially if the plants can affect the time pollinators spend within their flowers to increase their fidelity.

“The ability to discriminate approaching pollinators based on their distinctive vibroacoustic signals could be an adaptive strategy for plants,” said Barbero. “By replying to their proper vibroacoustic signal — for instance, an efficient pollinator’s — plants could improve their reproductive success if their responses drive modifications in pollinator behavior.”

While it’s clear that buzzing sounds can trigger plants’ responses, it’s less clear whether plant acoustics can also influence insect behavior — for example, whether sounds from plants can draw in a suitable pollinator.

“If this response from insects is confirmed, sounds could be used to treat economically relevant plants and crops, and increase their pollinators’ attraction,” said Barbero.

The team is conducting ongoing analyses comparing snapdragon responses to other pollinators and nectar robbers.

“The multitude of ways plants can perceive both biotic factors — such as beneficial and harmful insects, other neighboring plants — and abiotic cues, like temperature, drought, and wind in their surroundings, is truly astonishing,” Barbero said.

The project, “Good Vibes: How do plants recognise and respond to pollinator vibroacoustic signals?” (grant RGP0003/2022), is funded by the Human Frontier Science Program and is a collaborative effort between the University of Turin, I²SysBio in Valencia, and the Centre for Audio, Acoustics and Vibration at the University of Technology Sydney.

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2aEAa5 – Miniature Directional Sound Sensor Inspired by Fly’s Ears

Daniel Wilmott – dwilmott@nps.edu
Fabio Alves – fdalves@nps.edu
Gamani Karunasiri – karunasiri@nps.edu

Department of Physics
Naval Postgraduate School
Monterey, CA 93943

Popular version of paper 2aEAa
Presented Tuesday morning, November 3, 2015
170th ASA Meeting, Jacksonville

Humans and animals that posses a relatively large separation between ears, compared to the wavelength of sound, utilize the delay of sound arrival between ears to sense its direction with relatively good accuracy.  This approach is less effective when the separation between ears is small, such as in insects.  However, the parasitic Ormia Ochracea fly is particularly adept at finding crickets by listening to their chirps, though the separation of their ears is much smaller than the wavelengths generated by the chirps. The female of this species seek out chirping crickets (see Fig. 1) to lay their eggs on, and do so with an accuracy of few degrees. The two eardrums of the fly are separated by a mere 1.5 millimeters (mm) yet it homes in on the cricket chirping with 50 times longer wavelength where the arrival time difference between ears is only a few millionths of a second.  It is interesting to note that Zuk and coworkers found that “between the late 1990s and 2003, in just 20 or so cricket generations, Kauai’s cricket population had evolved into an almost entirely silent one” to avoid detection by the flies.  The studies carried out on the fly’s hearing organ by Miles and coworkers in the mid-90s found that workings of the fly ears are different from that of the large species and are mechanically coupled at the middle and tuned to the cricket chirps giving them remarkable ability locate them.

1 - Ormia Ochracea fly

Figure 1. Ormia Ochracea uses direction finding ears to locate crickets.

In this paper, we present a miniature directional sensor that was designed based on the fly’s ears, which consists of two wings connected in the middle using a bridge and fabricated using micro-electro-mechanical-system (MEMS) technology as shown in Fig. 2.  The sensor is made of the same material used in making microchips (silicon) with the two wings having dimensions 1 mm x 1 mm each and thickness of less than half the width of human hair (25 micrometers).  The sensor is tuned to a narrow frequency range, which depends on the size of the bridge that connects the two wings.  The vibration amplitudes of the sensor wings (less than one millionth of a meter) under sound excitation was electronically probed using highly sensitive comb finger capacitors (similar to tuning capacitors employed in older radios) attached to the edges of the wings.  It was found that the response of the sensor is highly directional (see Fig. 3) and matches well with the expected behavior.

2

Figure 2. Designed (left) and fabricated (right) directional sound sensor showing the comb finger capacitors for electronically measuring nanometer scale vibrations generated by incident sound.  The size of the entire sensor is less than that of a pea.
3

Figure 3. Measured directional response of the sensor tuned to 1.67 kHz for a set of sound pressures down to 33 dB.

The sensor was able to detect sound levels close to that of a quite whisper 30 decibel (dB) which is thousand times smaller than the sound level generated in a typical conversation (60 dB).  The sensor has many potential civilian and military applications involving localization of sound sources including explosions and gunshots.