The screams of thirsty plants may prompt some moths to lay eggs elsewhere

Once you’re a female moth, finding the proper plant to host your young may be as straight forward as taking a detailed listen.

When low on water, some flora make high-pitched clicking noises, inaudible to humans. Female moths, using their sensitive hearing, appear to key in on the distressed din and steer clear so that they are ready to lay their eggs on flora so to higher feed their caterpillars after hatching, researchers report November 14 at bioRxiv.org.

Ultrasonic thirsty plant clicks were discovered in 2023 by colleagues of Rya Seltzer, an entomologist at Tel Aviv University (SN: Three/30/23). She and her team wondered if moths — which may theoretically hear within the high frequency range of the clicks — would maybe use that information to their advantage when selecting flora to host their young.

The researchers placed fertile female Egyptian cotton leafworm moths (Spodoptera littoralis) in an arena with speakers playing the sounds of a dehydrated tomato plant on one side and silence on the opposite. The moths preferentially laid their eggs near the speaker making the distressed clicks, the team found.

“Alternatively, the plot thickened after we introduced actual flora into the setup,” Seltzer says.

When the team ran experiments with no speakers, but a hydrated tomato plant on one side of the arena and a thirsty one on the opposite, the moths switched their preference, opting for the silent hydrated plant. In one experiment, the team placed a hydrated plant on each and every side of the arena and a speaker on one amongst those sides playing distressed clicks. The moths laid more eggs on the plant on the silent side.

Without a actual flora present for moths to identify with other senses, the researchers write, the sounds of a drying plant are sole indicators of vegetative life, suggesting only one option for raising caterpillars. But with get entry to to flora that the moths can see and smell, the insects can now choose from flora, fending off people that sound stressed out and opting for a potentially fitter host.

“Female moths no longer only recognize these sounds as being made by flora but also connect them to the physiological state of the flora,” Seltzer says. “It’s fascinating to have in mind how an awful lot information exists lower than the perimeter of human hearing.”

Notably, these moths had no prior exposure to flora, being reared entirely within the lab. So being attuned to the flora’ clicking is deeply rooted in their genetics, Seltzer says.

Björn Thorin Jonsson, a biologist on the University of Graz in Austria, notes: “Once you may perhaps likely be in a position to have the ability to also detect an acoustic cue that is widespread, reliable and may be advisable for selecting better food or more suitable [egg-laying] web sites, why no longer use it?”

Sensory biologist Fernando Montealegre-Zapata of the University of Lincoln in England wonders if there may be agricultural applications of the flora’ noise. “May the playback of stress acoustic cues be implemented in integrated pest management programs to discourage moths from [laying eggs] on healthy flora?”

Seltzer thinks the form of response to plant noises may be widespread among insects and flora. Many insects have ultrasonic hearing ready to hearing plant clicking.

“I have in mind that this discovery is just the start of working out the acoustic interactions between animals and flora,” she says.