Where Did Butterflies Come From? This Scientist Is On the Case

When Akito Kawahara was 8 years old, his father took him on a members-only tour of the insect collection at the American Museum of Natural History in New York City. His father, the renowned conceptual artist On Kawara, had introduced him to butterfly collecting early, and Akito had already amassed about 500 of his own specimens. Seeing the enormous cabinets and extensive floor displays of butterflies and other insects on the museum’s fifth floor, Akito was thrilled, but what really captured his attention was an unassuming chart posted on the door of a curator’s office. It was a phylogeny of butterflies—an evolutionary family tree—and it contained many blank spaces.

“I was so surprised that scientists didn’t know everything about this, and it became my childhood dream to figure out where butterflies came from, how they evolved and how they’re related to each other,” says Kawahara, now a 45-year-old entomologist at the University of Florida.

This past May, working with nearly 90 co-authors from six continents, he published the results of a massive global study of butterfly evolution, based on DNA samples from 2,300 butterfly species. Not only does it fill in the gaps on the phylogeny chart he saw as a child, but it also presents a completely new origin story for these charismatic insects. Most scientists thought they evolved in Australasia, but it seems most likely that the first butterflies appeared in North and Central America. The ancestor of butterflies was a nocturnal moth that became day-flying here, 101.4 million years ago.

For Kawahara, the eight-year-long study was intensely personal, because he found it impossible to separate the science of butterfly evolution from memories of his father. “I became interested in butterflies because of him. He was the one who inspired me to follow my passion and become a butterfly scientist. And he was with me that day at the [museum] when I saw the poorly resolved butterfly phylogeny and dreamed of completing it.”

When Kawahara was 4 years old, his parents noticed that he was scared of insects and would run away from them. To help him overcome this fear, his father started taking him for walks in the parks of suburban Tokyo, looking for insects, talking about insects and carrying a butterfly net. “I still remember the first butterfly I collected,” says Kawahara, his eyes brightening at the memory. “It was near my grandmother’s house. I remember the exact place where the butterfly landed. It was a snout butterfly. I had seen it in books, and now it landed right in front of me. I remember my hands shaking and my dad helping me to catch the butterfly.”

Kawahara still has that specimen in his personal collection in Tokyo, which now numbers between 5,000 and 10,000 and also serves as a remembrance of his father. In his youth, the family divided its time between Tokyo and New York—Kawahara attended schools in both cities—and on weekends, his father would take him on butterfly collecting trips. On Kawara also traveled extensively to create his art and sometimes brought his son along, plus their butterfly equipment. As a boy, Kawahara gathered specimens from Singapore, Hawaii, Alaska, California and all over Japan.

He chose Cornell University for his undergraduate studies because of its excellent entomology department. As a graduate student at the University of Maryland in 2006, Kawahara named a newly described Costa Rican moth species after his father—Beltheca oni—and later took his dad into the mountains of Costa Rica to find examples of the species.

Moths were the focus of Kawahara’s early career. He remains fascinated by them and likes to point out that butterflies are basically just moths that fly by day. Approximately half of moths have hearing abilities, and he’s particularly interested in a group that can hear bat sonar and make acoustic signals to “jam” the sonar and escape predation. In 2014, Kawahara partnered with two fellow entomologists—Naomi Pierce from Harvard and David Lohman from City College of New York—and soon secured a $2.5 million grant from the National Science Foundation to study butterfly evolution. His father died, at age 81, a few months before they wrote the proposal, but he had already planted the seed of the project in Kawahara’s mind: “One of our last conversations was about insect evolution, and he said, ‘What about butterflies? How did they evolve? You were always wondering about this as a boy.’”

For the next five years, Kawahara’s life was taken over by travel and fieldwork. He went to the Marquesas Islands in French Polynesia, to Borneo, Japan, Malaysia, Vietnam, India, New Zealand, Canada, parts of Africa and many different locations in South America. In the Amazon and the Andes, he and his assistants collected American moth-butterflies—butterflies that have become nocturnal like their distant ancestors and developed hearing organs that can detect bat sonar. “You have to collect them at night with lights, like moths,” he says.

Other butterfly species live only at the top of the rainforest canopy, and they had to be lured down with bait. “Rotting fish is one way,” Kawahara says. “Other people say rotting fruit. But regardless, the bait always smells horrible and it’s absolutely repulsive. A combination of chicken poop and urine works the best, I think, but different butterfly people have their own recipes.” Male butterflies are particularly attracted to other creatures’ excretions. “They use minerals to make pheromones, or female-attracting chemicals.”

It wasn’t even necessary to kill the butterflies they collected to extract their DNA. All the researchers needed was a tiny piece of one leg; the butterflies could then be released to live out the rest of their short lives—two to four weeks on average, although some species live between six months and a year. In addition to their work in the wild, the researchers were able to obtain DNA from butterfly specimens in museums around the world, from the small number of fossilized butterflies that have been found, primarily in Colorado—and from Kawahara’s personal collection.

Then came the enormous task of analyzing the data. The team had four supercomputers running simultaneously in Bonn, Germany; at the University of Florida; at the Smithsonian National Museum of Natural History in Washington, D.C.; and at Brigham Young University in Utah. Processing more than 370 million individual DNA pieces, or nucleotides, through models of DNA evolution, the supercomputers calculated the best hypothesis or probability of the butterfly evolutionary tree; then, based on dating and fossils, they estimated the age of every possible branch in the tree.

The result is a beautiful, elaborate diagram that looks more like a wheel than a tree. Besides the breakthrough discoveries into where and when butterflies originated, it demonstrates that 36 tribes of butterflies need to be reclassified—and supports Kawahara’s 2019 hypothesis on how and why moths started flying in the day. Since the oldest intact fossilized butterfly was 55 million years old, and bats evolved in the same era, many scientists had thought that a group of moths became day-flying to escape bat predation. Now we know, thanks in large part to Kawahara’s revelatory work, that butterflies originated over 100 million years ago—some 35 million years before bats. Kawahara thinks that it was bees, not bats, that caused the advent of day-flying moths.

Many studies have suggested that bees, which emerged some 125 million years ago, may have triggered plants to evolve nectar and colorful flowers to attract these busy, efficient daytime pollinators. “All these flowering plants were a food opportunity, and we think the first day-flying moths took advantage of it,” Kawahara says. “They adapted to see color, search for flowers and drink nectar. So butterflies should thank bees, I guess, is the consensus.” Using a technique called ancestral state reconstruction, which maps the likeliest ranges of butterfly species and caterpillar host plants back in time through the family tree, researchers concluded that the first butterfly caterpillars probably fed on just one group of plants: the legumes, or American bean plants.

By assigning a geographic area to every species in the study, and then using the DNA tree and supercomputers to calculate the probability that their ancestors were there in the past, researchers were able to form a hypothesis about the spread of butterflies around the world. First they fluttered east across North America and down into South America. Then they dispersed in waves to Australia, Asia, India, Africa and finally, around 30 million years ago, to Europe. Today there are an estimated 19,500 species, distributed all over the world except Antarctica, even on remote and isolated islands.

Asked why some butterflies became so beautifully colored, Kawahara offers three generally agreed-upon reasons. “They’re displaying their chemical defense to predators, so birds and lizards, when they see a bright red butterfly, they think, ‘No, I’m not going to eat this thing because it’s toxic.’ Then there’s mimicry. Many butterflies look like the brightly colored toxic ones, but they’re not chemically defended. And lastly for mating. They use their colors to flash and display to the opposite sex.”

His next project is focused on building a more detailed picture of butterfly evolution, by using a much larger and more comprehensive DNA sampling than the 2023 study. For example, he hopes to narrow down where in North America the first butterflies originated. Kawahara has also secured part of a $4 million collaborative grant from the National Science Foundation to study moth and butterfly silk, with a view to engineering stronger synthetic bioproducts based on silk.

In the last few years, partly because he has been so busy with work, Kawahara has stopped adding to his personal collection, which contains so many memories of his father and his boyhood. Instead, he has been helping his 9-year-old daughter Kaya Luna Kawahara to build up her insect collections. She particularly likes beetles, caterpillars—and the luna moths that inspired her middle name.

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Flights of Fancy

Representing the souls of the dead, and sometimes art itself, these winged muses have inspired poets for millennia

By Ted Scheinman

The Chinese bard Li Bai used the butterfly in the eighth century A.D. to evoke the limits of human perception in these verses about the fourth-century B.C. philosopher Zhuangzi:

Zhuangzi in dream became a butterfly,

And the butterfly became Zhuangzi at waking.

Which was the real—the butterfly or the man?

Who can tell the end of the endless changes of things?

...So must rank and riches vanish.

You know it, still you toil and toil,—what for?

Celebrated as the supreme master of the haiku, the 17th-century Japanese poet Basho captured the poignancy of change that refuses to come:

Not grown to a butterfly,

this late in autumn—

a caterpillar.

William Wordsworth, one of England’s poet laureates, who helped launch the Romantic movement in letters, was delighted by butterflies and celebrated their stylish indolence in these verses, written in April 1802:

I’ve watched you now a full half-hour,

Self-poised upon that yellow flower;

And, little Butterfly! indeed

I know not if you sleep, or feed.

Emily Dickinson frequently invoked these creatures, often by way of underlining human folly, as in this circa 1881 poem:

The Butterfly upon the Sky,

That doesn’t know its Name

And hasn’t any tax to pay

And hasn’t any Home

Is just as high as you and I,

And higher, I believe,

So soar away and never sigh

And that’s the way to grieve—

The abolitionist and Unitarian minister Thomas Wentworth Higginson extolled the butterfly as the supreme symbol of the world’s mystery in these lines, published in 1889:

Thou spark of life that wavest wings of gold,

Thou songless wanderer ’mid the songful birds,

With Nature’s secrets in thy tints unrolled

Through gorgeous cipher, past the reach of words …

Richard Grant | | READ MORE

Richard Grant is an author and journalist based in Tucson, Arizona. His most recent book is The Deepest South of All: True Stories from Natchez, Mississippi.