Recent research has uncovered a fascinating phenomenon: when low on water, some plants emit high-pitched clicking noises, inaudible to human ears but detectable by certain insects. These ultrasonic “screams” might be nature’s way of signalling distress—and they don’t go unnoticed.

New research published in the journal BioRXiv found that female moths use their sensitive hearing to listen to these ultrasonic signals steer clear of thirsty plants when laying eggs. This behaviour ensures their caterpillars hatch on healthier plants, with a better chance of survival.

The researchers placed fertile female moths in a controlled arena. When given a choice between a hydrated tomato plant and a thirsty one, the moths overwhelmingly chose the silent, hydrated plant. But the researchers didn’t stop there.

In another experiment, two hydrated plants were placed in the arena, with a speaker next to one of them playing recorded distressed clicks. Again, the moths avoided the “noisy” plant, favouring the silent one. These results suggest that the sounds alone, even without visual or olfactory cues, are enough for moths to make a decision.

What’s even more fascinating is that these moths had no prior exposure to plants. Raised entirely in a lab, they had no opportunity to learn this behaviour. Their response to the ultrasonic signals appears to be hardwired in their genetics, highlighting the intricate connections between insects and plants in nature.

This discovery isn’t just a marvel of biology; it could have practical applications in the real-world. One could be pest management. By broadcasting ultrasonic distress signals, farmers might discourage moths from laying eggs on healthy crops, potentially reducing the need for chemical pesticides.

Many insects have ultrasonic hearing, suggesting that this type of interaction might be widespread.

This research invites us to rethink what we know about communication in nature. Beneath the threshold of human hearing lies a hidden world where plants and insects exchange critical information—a world we are only beginning to understand.

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