When They Hear Plants Crying, Moths Make a Decision

A new study suggests that the insects rely on the sounds made by distressed vegetation to guide important reproductive choices.

You may not want to sit next to a crying baby on an airplane. Apparently, moths feel the same way about plants.

When some plants are dehydrated or under some other form of stress, they cry a mournful melody made of ultrasonic clicks. Some moths are able to hear those clicks, and researchers now say they have discovered that the insects may interpret the sounds as a cue to choose on which plant to lay their eggs. The finding was described in a paper that was published online last month and has been submitted to the journal eLife.

“This is new,” said Rya Seltzer, an entomologist at Tel Aviv University and an author of the study. “Plants emit sounds, and insects are really listening to that. They’re tuned to that specific sound, and they know the meaning, and they consider it.”

In an earlier study, researchers showed that some plants emit ultrasonic clicks when under stress. Those sounds are imperceptible to people but fall within the hearing range of other animals, including insects.

This discovery lit a spark for Dr. Seltzer and her team: What if some insects actually interpret those sounds and use them to make decisions?

The researchers worked in a laboratory with a moth species called the Egyptian cotton leafworm. This insect is able to hear the sounds produced by some plants. The researchers wanted to know whether female leafworms would use the clicks to decide where to lay eggs, one of the most important choices in their lives.