Female moths detect ultrasonic clicks emitted by stressed plants, utilizing these sounds to inform their choice of egg-laying sites. This discovery suggests that insects can perceive and respond to airborne ultrasonic vibrations from plants, a phenomenon previously thought undetectable by animals.nThe Egyptian cotton leafworm moth (Spodoptera littoralis) possesses tympanic ears sensitive to frequencies between 20 and 60 kHz, with peak sensitivity around 38 kHz. Many plant stress clicks occur within this range.
Experimental Findings
Experiments showed that moths used plant sounds for decision-making regarding egg-laying. In environments without plants, moths preferred to lay eggs near a speaker playing recorded plant stress sounds. This preference ceased when the moths were deafened, indicating that hearing was the mechanism of response.
Conversely, when healthy plants were present, moths avoided laying eggs on plants from which stress sounds were emitted, choosing silent, healthy plants instead. This suggested that moths interpreted the sounds as a warning in the presence of real plants.
Professor Yossi Yovel of Tel Aviv University, a co-author of the study, stated that researchers hypothesized animals capable of hearing high-frequency plant sounds might respond and make decisions based on them. Professor Lilach Hadany, another co-author, explained the focus on female moths seeking optimal sites for their larvae, hypothesizing moths might avoid stressed plants.
Plant Communication and Moth Behavior
Further experiments in longer arenas indicated moths spent more time near areas with plant sounds before making egg-laying decisions. The response was specific to plant sounds, as female moths did not show preference for areas emitting male courtship sounds, which fall in a similar frequency range.
Moths' antennae also showed differences in odor detection between drying and hydrated plants, indicating an integration of both sound and smell cues. The sound levels and click rates used in experiments simulated natural conditions, with click rates reaching approximately 20 per minute in real tomato plant patches.
Broader Implications
This research indicates that plant sounds can guide insect behavior, adding to the understanding of inter-species communication beyond sight and smell. Scientists suggest that other animals, such as pollinators or predators, might also use these sounds. While plant clicks are likely a byproduct of water loss, they serve as significant cues in ecological interactions. The study, published in the journal eLife, highlights this as a largely unexplored field of acoustic interaction between plants and animals.