Insects and pollinators
Hawkmoths evolved acoustic defenses multiple times
Researchers found that male hawkmoths developed separate genital sound mechanisms across thirty million years to disrupt hunting bats.
Reported by Phys.org · · 2 min read
Male hawkmoths possess remarkable anatomical tools that can save their lives during nocturnal encounters with hungry predators. By rubbing specialized scales located on their reproductive organs against their abdomens, these night-flying insects generate ultrasonic noise capable of interfering with the echolocation signals bats rely on while hunting.
Predatory bats and nocturnal moths have engaged in a protracted evolutionary conflict spanning millions of years. In this ongoing dynamic, adaptations by one group prompt defensive counter-tactics from the other. To explore the origins and diversity of these acoustic defenses, a research team led by Paul K. Masonick from the University of Florida analyzed hawkmoth behavior and anatomy across numerous species.
The investigators tested how living specimens reacted to audio playbacks of hunting bats as well as soft physical restraint meant to imitate capture. Whenever the insects generated ultrasonic pulses, researchers recorded the audio. They subsequently examined the reproductive morphology of 124 species and traced evolutionary lineages across 310 moth species to reconstruct how these acoustic systems arose.
Writing in the Royal Society journal Proceedings B, the team reported that ultrasound-based defenses against bats arose on separate occasions up to seven times across approximately thirty million years. Rather than relying on a single uniform adaptation, different hawkmoths established three separate physical ways to create sound.
Each mechanism depends on friction between modified genital scales and distinct abdominal surfaces, which include companion scales, microscopic spines, or raised nodules. These three anatomical arrangements yielded acoustically diverse results, showing variations in pitch frequencies, burst durations, and the total time insects spent producing noise.
Hearing ability also shaped these protective strategies. Hawkmoths equipped with auditory organs tended to generate sounds with a greater capacity to disrupt bat biosonar, indicating a functional connection between listening for predators and emitting jamming signals. Meanwhile, several species that lacked hearing organs still generated ultrasound when touched, suggesting their sounds might startle predators or imitate other species rather than jam sonar.
