Butterflies have "listened" to plants when choosing locations for laying their eggs.

In a previous study, Israeli scientists found that when dehydrated or under other types of stress, some plants emit high-frequency "cries" that are inaudible to the human ear, resembling clicks. The researchers proposed that these sounds serve as a means of communication between plants and organisms within their ecosystem, including members of both flora and fauna.

A recent study conducted by another group of researchers from Tel Aviv University (Israel) has confirmed this hypothesis. The specialists submitted an article about their discovery to the journal eLife and published it on the preprint site bioRxiv.org.

Learning about the clicks produced by plants, entomologist Rya Seltzer (Rya Seltzer) theorized that these high-frequency sounds, which fall within the hearing range of insects, may convey specific information to them.

To test this hypothesis, the researcher, along with her colleagues, conducted a series of experiments with the moths of the species Spodoptera littoralis, also known as the "Egyptian cotton leafworm." These butterflies, found in Africa, the Mediterranean, Europe, and the Middle East, are classified as agricultural pests. Their caterpillars, which hatch from eggs laid by the female on leaves, damage a variety of crops and ornamental plants, including tomatoes, eggplants, potatoes, tobacco, roses, and others.

In the initial phase, the scientists demonstrated that female S. littoralis preferred to lay their eggs on the leaves of healthy, well-watered plants, which were less likely to suffer from water shortages and would provide the caterpillars with sufficient food.

In a series of subsequent experiments, the researchers played back sounds previously recorded near a wilting plant — a tomato — while simultaneously observing the behavior of the butterflies.

In one test, two healthy and well-hydrated tomato bushes were placed in the experimental area. When high-frequency clicks, indicating plant wilting, were played near one bush, it turned out that the female butterflies preferred to lay their eggs on the other, "silent" specimen. This preference disappeared when the butterflies were deafened, confirming that the choice was based on hearing. The experimenters also verified that the signals from male butterflies did not influence the females' egg-laying decisions.

In a comment to The New York Times, Seltzer stated that female S. littoralis not only recognized the high-frequency clicks being played but also understood that they indicated the presence of plants. The butterflies perceived these sounds as clues about the plant's condition and factored these signals into their decisions on where to lay their eggs.

Ecologist Jodi Sedlock (Jodi Sedlock) from the University of Wisconsin–Lawrence (USA) positively assessed her colleagues' research but noted that the reason why butterflies pay attention to plant sounds remains unclear. She suggested that the scientists continue their experiments in natural settings, as laboratory conditions differ from those in the wild.

Rya Seltzer agreed that the study's results require further validation and clarification. At the same time, she noted that many plants emit ultrasonic signals when stressed, and many insects are capable of perceiving them, making such "communication" likely a common phenomenon.