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The zebra swallowtail butterfly is stunning, with long, sword-like tails, black-and-white stripes, and a bold red stripe on its underwing to warn would-be predators: Do not eat me, for I am poison. Once you’ve seen this butterfly, there’s no mistaking it for another. Although its host plant, the pawpaw, is native to Pittsburgh, no sightings of this butterfly had been reported in 87 years.
This summer, that’s changed.
On the afternoon of June 21, Daniel and Tamaryn Brown were in their yard in Greenfield, and Daniel had just lamented seeing few butterflies this year. Just then, an eastern tiger swallowtail flitted by. The couple marveled at the synchronicity of its appearance. Later, as they were going inside, a second butterfly crossed in front of Tamaryn. This one, however, was unfamiliar. “It looks like a zebra,” she remarked.
Four years earlier, Daniel planted his first pawpaw tree, both for its edible fruit and because it’s not a preferred food of deer. He’d given the zebra swallowtail only passing thought. As it flitted from tree to tree in front of him, the butterfly took center stage.
Daniel had recently joined a Pittsburgh naturalists’ text thread, where he recalled a discussion about these distinct butterflies, so he uploaded the pictures and a brief narrative. He was not aware of the full significance of his sighting until the responses came pouring in.
One member of this chat is Gabrielle Marsden, a naturalist who has been fervently urging everyone within earshot for the past several years to consider the zebra swallowtail — and to get busy planting its host plant, the pawpaw.
In her quest to document historic occurrences of the zebra swallowtail and to promote its return, she has pored over archives, slogged through natural areas, and even written a zebra swallowtail paean on her ukulele (“I’m not dead, I should be in Pittsburgh…”). So when Gabrielle saw Daniel’s messages, and the photo of a zebra swallowtail, she was electrified. “WHERE ARE YOU?” she replied in all caps.
By the time Gabrielle arrived in Greenfield, the butterfly was gone. But it had left something behind every bit as thrilling as the initial sighting: eggs.
Daniel also discovered the first so-called instar caterpillars, which meant the butterfly had also visited a few days earlier. Daniel and Gabrielle collected eggs and spent the next few weeks raising larvae, feeding them pawpaw leaves, watching the formation of chrysalis, and, as luck would have it, witnessing the emergence of metamorphosed zebra swallowtails.
It had been a long time coming, and the life cycle was made possible because the Greenfield garden provided exactly what this single species required.
“It’s amazing,” Gabrielle says. “I wasn’t anticipating anything like that happening in five to 10 years.”
Where have you been?
To find zebra swallowtail butterflies, you must look for pawpaws; Its larvae evolved to feed exclusively on plants of the genus Asimina. Males rarely stray far from pawpaw thickets, which is where they find their mates, and females must return to lay their eggs.
Pawpaws have a long history in Southwestern Pennsylvania. It’s a story I became fascinated with, and chronicled in my book, “Pawpaw: In Search of America’s Forgotten Fruit.” Thousands of years ago, Indigenous people gathered and ate the fruit. Meadowcroft Rockshelter archaeologists have recovered the fruit’s seeds in archaeological layers dating back to 340 B.C.
In the late 1700s, famed naturalist François André Michaux marched through the rugged region and noted, “At Pittsburgh some persons have succeeded in making from [pawpaw] a spirituous liquor …” In 1916, when the American Genetics Association launched a contest to find the best and largest pawpaw in the country, one stand-out submission came from Pittsburgh’s Allegheny Observatory. And in 1953, botanist and conservationist O.E. Jennings reported, “Formerly considerable quantities [of fruit] reached the Pittsburgh markets via the packets from the upper Monongahela Valley.” There were pawpaws aplenty.
Yet, with Pittsburgh at the edge of range for both pawpaws and zebras, it was relatively easy for this specialist butterfly to be chased out, and wiped out, by heavy industry. By the early 20th century, both species were becoming rare on Pittsburgh’s waterways.
Although we’re unlikely to know the precise abundance of zebra swallowtails before industrialization, museum specimens help to paint a picture.
Kevin Keegan is a collection manager in the Section of Invertebrate Zoology at the Carnegie Museum of Natural History. When he heard of the zebra swallowtail sighting, he went to his museum’s collection and snapped a photo of the last confirmed sighting: 1937, in Highland Park. A few decades earlier, they had been even more abundant. In fact, there are more than 50 specimens in the museum’s collection, the bulk of which were collected between 1899 and 1901, from around Sharpsburg, Pittsburgh and Swissvale.
Today, there are a few remnant pawpaw patches in Pittsburgh parks and green spaces. As the pawpaw has received renewed interest, more people grow them in their outdoor spaces. But none of it seems to be enough to lure, or sustain, a breeding population of zebra swallowtails. Our pawpaw patches just aren’t as sprawling as those found within the species’ core ranges.
But they’ve never been far. Zebra swallowtails are frequently observed in both Wheeling and Morgantown, West Virginia.
Curt Lehman, a leading butterfly expert in Southwestern Pennsylvania, has scoured the Pittsburgh region for butterflies for nearly 60 years, and he has seen zebras near Perryopolis, at Ohiopyle State Park, and at the Friendship Hill National Historic Site near Point Marion. Ten years ago, the first recorded sighting in Beaver County was observed. In 2019, a zebra swallowtail was reported in Washington County, and just last summer, another in Greensburg.
And then this summer, the conditions were right for Pittsburgh to be next.
Zebra swallowtails typically stay near pawpaw patches, but they have been known to go a-wandering. When it’s hot, like it was in June, they can go quite far. Over the years, they’ve been observed in southernmost Ontario, southeast Wisconsin, the greater Chicago area and even parts of New England.
Entomologist Jaret Daniels, director of the McGuire Center for Lepidoptera and Biodiversity at the Florida Museum of Natural History, surmises that this heat wave may have led the Greenfield zebra to Pittsburgh (or, at least, kick-started its journey).
“If they don’t have anything to lay eggs on at a local area, they’re going to go searching for it,” he says, “if there are urban parks or flyways, or riverine systems that they can move between areas, they’ll use those as natural flyways.”
As the climate continues to warm, they’re likely to continue exploring northward. And if their host is here, they just might stick around.
Could there be more?
Curt Lehman, who created the Butterflies and Moths of Pennsylvania Facebook group, says this summer’s sighting was a big deal for the local community. And it’s got him thinking: “If there’s one, there’s got to be some more funneling through.”
His intuition appears to be correct.
Seven days later, there was another. On June 28, Joe and Diane Kostka, who have been growing pawpaw for two decades, saw a zebra swallowtail flit through their hilltop orchard in Natrona Heights, in northeast Allegheny County. The next day, Joe sent a text: “Took 20 years. Here’s hoping they use the yard to reproduce.” Unfortunately, the butterfly moved too quickly for a picture — it’s an erratic flyer — and as far as the Kostkas are aware, it never returned.
The cryptic nature of this butterfly begs a couple more questions: Have there been more strays we’ve missed? And is it possible they’ve been hiding in plain sight?
As it turns out, there was at least one other Pittsburgh sighting that predates this summer’s. In May 2010, Lenore Raffle was in the garden of her Beechview home, where she’d planted flowers and shrubs to attract butterflies, when a zebra swallowtail landed on a butterfly bush. She quickly snapped a picture.
“I knew what it was right away, and I was shocked,” Raffle says. “But I don’t think I really looked into how rare they were in our neck of Pennsylvania.”
But 14 years ago, citizen science reporting apps like iNaturalist were less widely used. Raffle has since joined those platforms and regularly reports sightings of birds, insects and plants. But she’d never gone back and uploaded the zebra swallowtail photo to iNaturalist, or Butterflies and Moths of North America, so it has not been officially recorded.
The photo, however, is unequivocal. There’s no mistaking the zebra swallowtail.
What’s Next?
Daniel and Gabrielle are still jubilant about the experience. Daniel is committed to transforming his yard into a wildlife oasis and Gabrielle hopes the sighting will lead to larger-scale restoration of Pittsburgh’s riparian zones.
But what about the butterflies themselves — the ones seen here this summer?
The Natrona Heights stray was never seen again. And the mother that Daniel saw, whose progeny he and Gabrielle helped to raise, returned to Daniel’s garden twice more and laid a total of four broods of eggs. (Where it went in the interval was anyone’s guess, and remains an enthralling mystery). Since adult zebra swallowtails only live up to six months, its only trace is likely its offspring now flitting around the Steel City. Whether their offspring will survive our winters in chrysalis is another unknown, but the Carnegie collection seems to indicate yes.
“They’re going to live their best, glorious life,” Gabrielle says, “because, I mean, look at them, why shouldn’t they?”
Andrew Moore is the author of “Pawpaw: In Search of America’s Forgotten Fruit,” which was a James Beard Foundation Award nominee in Writing & Literature. In late August, his homegrown pawpaws can be found at the East End Food Co-Op. His next book, “Beasts in the East: A Story of Restoration and Rewilding in the American East,” will be published by Mariner Books next summer.
