Moths, it seems, may be just as sensitive to the sounds of stress as humans are to crying babies. A new study reveals that certain moths can hear ultrasonic clicks made by plants under stress and may use these sounds to decide where to lay their eggs.
The research, led by entomologist Rya Seltzer at Tel Aviv University, was published online last month and is awaiting review in the journal *eLife*. The study suggests that moths are not only capable of hearing these sounds, but they also appear to interpret them, considering them when making critical reproductive decisions.
“These sounds are specific, and insects are really tuned to them,” said Seltzer. “They know the meaning and respond accordingly.”
In a previous study, scientists discovered that plants emit ultrasonic clicks when they are stressed, such as when they are dehydrated. These sounds, though inaudible to humans, fall within the hearing range of many animals, including insects. Inspired by this, Dr. Seltzer and her team wondered if moths might use these sounds to make decisions about where to lay their eggs, an important choice for the survival of their offspring.
The researchers focused on the Egyptian cotton leafworm, a moth species known to hear plant-generated sounds. Female moths, in particular, must choose where to lay their eggs, a decision that will directly impact the success of their larvae.
Initially, the team confirmed that female moths typically preferred to lay their eggs on healthy plants, which are more likely to provide sufficient food for their larvae. But then they took their experiment a step further.
In a controlled setting, they offered the moths two tomato plants: one healthy and silent, the other healthy but emitting the distress signals of a dehydrated plant. The moths overwhelmingly chose the silent plant, even though both plants were equally hydrated. This suggests that the moths were using the ultrasonic clicks to assess the plant’s condition and avoid laying eggs on stressed plants.
“They’re not just responding to the presence of a plant,” said Dr. Seltzer. “They can interpret the sounds as a sign of the plant’s health.”
Jodi Sedlock, a sensory ecologist at Lawrence University, praised the study for its strong evidence but noted that more research is needed to understand the full implications. “It would be interesting to see how this plays out in nature,” she said, pointing out that laboratory conditions might not fully reflect real-world scenarios.
Seltzer agrees, emphasizing that further studies should explore how moths combine these acoustic cues with other sensory signals, such as scent. She believes this behavior may be widespread, as many insects can hear ultrasonic sounds and many plants produce them when stressed.
Until now, scientists believed that moths primarily used their ultrasonic hearing to detect mating calls or evade predators like bats. This study adds a new layer to the moths’ use of sound in their environment, suggesting that their acoustic sensitivity may have deeper evolutionary roots.
However, some researchers remain cautious. Francesca Barbero, a zoologist at the University of Turin, pointed out that certain key details were missing from the study, such as the number of eggs laid by the female moths in the experiments. Despite this, Barbero acknowledged that the study could pave the way for future research into how plants use sound to communicate.
As Seltzer and her team look ahead, they are hopeful that their findings will spark broader investigations into plant bioacoustics and the ways insects interact with the sounds around them.
Related topics: