Some of the most sophisticated sound-jamming hardware in nature belongs to hawkmoths, and evolution apparently invented it more than once. A study published Nov. 4 in the Proceedings of the Royal Society B finds that male hawkmoths evolved the ability to make ultrasonic sound with their genitals independently as many as seven times over roughly the past 30 million years.

The sounds — too high for people to hear — are produced when moths are attacked by bats. Researchers say they may startle the predators, warn them off, or jam the echolocation bats use to track prey in the dark.

An Arms Race Fought in Sound

Bats and moths have been locked in a nighttime contest for tens of millions of years. Bats hunt with sonar, sending out ultrasonic calls and listening for echoes. Moths have answered with ears tuned to bat calls, evasive flight and, in some groups, sounds of their own.

Insects have evolved bat-detecting ears independently at least 19 times, according to a 2013 study in Biology Letters that first showed hawkmoths answer bat attacks with ultrasound. Tiger moths make similar sounds with a vibrating membrane on the thorax. Hawkmoths, it turned out, use their genitals.

Nature World News covered that early work and a 2015 follow-up that traced the trait's origins to about 26 million years ago. The new study goes much further, testing far more species and examining the anatomy in detail.

Three Ways to Make the Same Sound

The team, led by entomologist Paul Masonick of the Florida Museum of Natural History, tested how male hawkmoths responded to recordings of attacking bats and to gentle handling meant to mimic capture. Of 143 species tested, 77 produced ultrasound, Science News reported.

In every case, the sound comes from a patch of enlarged, football-shaped scales on the valvae, paired genital structures males use to clasp females during mating. The moths rapidly slide these structures against modified parts of the abdomen. What differs is the surface they scrape.

In the scale-on-scale method, genital scales rub against other scales on the abdomen. In the scale-on-spine method, they rub against tiny spines. In the scale-on-nodule method, they scrape across small bumps. According to ScienceAlert, scale-on-scale sounds were shorter and more intermittent, scale-on-spine sounds longer and more sustained, and scale-on-nodule sounds the most variable.

Not every species makes noise. Of the 143 tested, 66 produced no ultrasound, which suggests other defenses carry the load for many hawkmoths. Earlier work found hawkmoths are fast, agile fliers, and many species have ears on their faces that can pick up bat calls. Sound production appears to be one tool among several rather than a universal trait.

That difference matters. The more sustained sounds were the most likely to match the features associated with jamming bat sonar. Females also make sounds, but with a different mechanism, since they lack claspers.

Convergence Is the Real Headline

The study's biggest finding comes from the family tree. By mapping sound production onto the evolutionary relationships of 310 hawkmoth species, the researchers found that the genital sound system arose independently at least four times and as many as seven, between roughly 5 million and 30 million years ago, phys.org reported.

This is convergent evolution, when unrelated lineages arrive at similar solutions to the same problem. Wings in bats and birds are a classic example. Here, separate hawkmoth groups facing the same relentless bat predation each built their own sound-making apparatus from slightly different parts.

"Our findings deepen our understanding of defensive bioacoustic adaptations in this iconic predator-prey system,"Masonick and his colleagues wrote. The team included entomologist Akito Kawahara of the Florida Museum and sensory ecologist Jesse Barber, now at the American Museum of Natural History.

Limits of the Evidence

The research combined field playback experiments, high-resolution imaging of museum specimens from the University of Florida and London's Natural History Museum, and phylogenetic analysis. That makes it a strong comparative study, but it has limits.

The researchers showed that moths produce these sounds when attacked and that the trait evolved repeatedly. They did not test, in this study, how well each sound type actually protects moths from bats in the wild. The exact function, whether startling, warning, jamming or even a role in courtship, remains untested for most species. The range of four to seven origins also reflects uncertainty in reconstructing deep evolutionary history.

A Hidden Soundscape With Real-World Stakes

The work offers a window into a nighttime soundscape people never hear. Hawkmoths are important pollinators, and several are familiar to U.S. gardeners. The pink-spotted hawkmoth studied by the team is the adult form of the sweet potato hornworm, and tomato and tobacco hornworms are also hawkmoth caterpillars.

Bats, meanwhile, eat enormous numbers of night-flying insects, including crop pests. Understanding how prey and predators adapt to each other helps scientists see how that balance holds, especially as bat populations face pressure from disease and habitat loss.

The research also shows the value of museum collections. Preserved specimens, some collected long before this study began, allowed the team to map sound-producing structures across far more species than could be tested alive. Kawahara has long described the museum's role as building a library of life that pairs specimens with records of behavior.

The next steps include field tests of how bats respond to each sound type and studies of how females produce their signals. For now, the hawkmoth stands as a striking example of evolution solving the same life-or-death problem again and again.

What Readers Want to Know

What did the new hawkmoth study find? Male hawkmoths evolved the ability to make ultrasonic sounds with their genitals independently as many as seven times over about 30 million years.

How do hawkmoths make the sounds? They scrape specialized scales on genital structures called valvae against other scales, tiny spines, or small bumps on the abdomen.

Why do they make these sounds? Likely to defend against bats by startling them, warning them, or jamming their echolocation. The exact function is still being tested.

Can people hear the sounds? No. The sounds are ultrasonic, above the range of human hearing.

What is convergent evolution? It is when unrelated groups independently evolve similar traits in response to similar pressures.

Are hawkmoths found in the United States? Yes. Several species are common in U.S. gardens, and their caterpillars include the tomato, tobacco and sweet potato hornworms.