Featured photo above: Two Miami blue butterflies perch on the tip of a plant, their gray wings facing back-to-back. (Photo courtesy Geena M. Hill)

By Brittney Miller, Reporting & Communications Intern / UF Thompson Earth Systems Institute (Published October 2020)

It looks like a blur, around the size of your thumbnail, fluttering from plant to plant. With tiny wings just as delicate as the petals it gently descends upon, it’s easy to overlook: a nickel-sized creature lost in the curves of coastlines carved by steady waves.

But Sarah Steele Cabrera said the insect stops her in her tracks every time she sees it.

“Most folks would walk right by it and not necessarily know they had seen a butterfly,” said Steele Cabrera, a research assistant in the Florida Museum of Natural History’s McGuire Center for Lepidoptera & Biodiversity.

And it’s not just any butterfly; the Miami blue butterfly is one of the rarest bugs in the world.

An abundance of Miami blue butterflies once flitted up and down Florida’s coastlines. Now, they can only be found in the Key West National Wildlife Refuge — a collection of islands about 15 miles west of Key West.

Researchers like Steele Cabrera trek to these islands via small boats, traversing clear blue waters in hopes of gleaning new knowledge about this insect. But sometimes, scientists can’t even find the enigmatic butterfly in its sole remaining residence.

“Even when I go to the sites where I know the Miami blue is found, it still can be a really rare sighting,” she said. “I’ve gone months at a time without seeing it, and that’s just how it goes.”

A story once thought to have written its last chapter, the rise and fall of the Miami blue butterfly highlights an extreme local example of global insect decline. As a whole, this worldwide bug loss is predicted to negatively impact pest management, waste removal and food supply for both humans and wildlife.

But luckily for the Miami blue, ongoing research efforts prove there’s still hope for this butterfly — still a spot for it in Florida’s myriad of changing landscapes.

The Fall of an Empire in Flight

The Miami blue butterfly wasn’t always confined to a remote collection of islands. In the 1950s, its gray patterned underwings could be spotted swooping around South and Central Florida coastlines — and particularly in Miami, where its name originated.

But today the Miami blue is absent throughout its historical range. Population numbers suffered dramatic losses throughout the 1970s and ‘80s, and its territory began to dramatically dwindle. After Hurricane Andrew decimated its last known population in the Florida Keys in 1992, the butterfly was thought to be extinct.

Less than a decade later in 1999, a researcher discovered a surviving population in the Bahia Honda State Park; then, more were found in the Key West National Wildlife Refuge in 2006. The population on Bahia Honda has since become extinct. The Miami blue’s current — and sole — residence remains on five islands in the National Wildlife Refuge.

“It was a butterfly so prolific and so abundant that nobody noticed there was a problem until, all of a sudden, people realized, ‘Oh, my gosh, they don’t exist anymore,’” said Kristie Killam, a park ranger in the Key West National Wildlife Refuge.

A large culprit of their decline? Coastal development, Killam said.

In 1950, when the butterfly was still recognized as common in the lower half of the state, Florida hosted a total population of just around 2.8 million people, according to the U.S. Census Bureau. But as the state’s population began to exponentially boom, the Miami blue’s habitat was destroyed to make way for homes and businesses. Its population plummeted. By the time the butterfly’s numbers hit nearly rock-bottom in 1992, Florida’s population had soared to 13 million people — a more than 300% increase in 42 years.

The Miami blue is known by scientists as a “habitat specialist,” Steele Cabrera said, which means it depends on specific plants or habitats for survival. In this butterfly’s case, it’s known to rely on three coastal plants: gray nickerbean, Florida Keys blackbead and balloon vine. When these plants are uprooted or paved over, the butterfly cannot survive.

Sometimes Goodbye is a Second Chance… for Research

With the bright blue upper surface of their wings back in sight, researchers like Erica Henry are taking advantage of their second chance with the Miami blue butterfly. Henry first started studying rare butterflies 12 years ago. Today, she’s a postdoctoral researcher at North Carolina State University.

Her preliminary research about the Miami blue focused on finding suitable ways to count and estimate the butterfly’s population numbers. But the better she became at counting them, the sooner she recognized a pattern: Rainfall seems to affect the Miami blue’s reproductive cycle.

When clouds over the Key West National Wildlife Refuge get dark and the water no longer reflects blue skies, the rain that descends upon the islands fuels plant growth. In turn, this spurs a greener habitat, Henry said, revitalizing the plants Miami blue caterpillars depend on.

“So, the pattern is that it will rain a bunch, and then there’s a little bit of a lag — there’s a little bit of time after that rain where you don’t see a whole lot of adult butterflies,” she said. “And then we get this flush of butterflies.”

But even when there are spurts of higher butterfly densities, this population has nowhere to go — and even if it did, the Miami blue’s half-inch wings can’t support a long journey. That’s why Steele Cabrera said it’s important to establish several populations in different habitat patches to bolster what researchers call a “metapopulation.”

She likened a metapopulation to several dots on a map, where each dot is its own Miami blue population in a different location. If they’re close enough, some butterflies might be able to travel between dots occasionally. This connection allows each individual population to be strengthened by the numbers in their surrounding communities.

“What can happen when you have a good, healthy metapopulation system is that if, say, something happened to one of those populations, one of those dots on the map… well, butterflies from those other populations can come in and recolonize that area,” she said.

Right now, there’s only one dot, Steele Cabrera said: the Key West National Wildlife Refuge. Without a metapopulation to reinforce it, that dot could be wiped from the map from just one cold snap, drought or massive hurricane. And that’s why she said the ultimate goal of her research is to cultivate more supporting populations and available habitat for this species by reintroducing adult butterflies into the wild.

These reintroduction efforts don’t start when the tiny creatures get released; they start in the lab. Like the age-old school projects where a child would raise a monarch from egg to caterpillar to pupae to butterfly, it’s a similar process for staff in the Daniels Lab within the McGuire Center for Lepidoptera & Biodiversity, where Steele Cabrera has worked the last five years.

Except multiply that one caterpillar by a couple hundred or thousand.

“It’s very hard work that is constant. It’s like having hundreds or thousands of little pets that need daily care,” she said.

Using the adult butterflies they've nurtured, the Daniels Lab has already began reintroducing the Miami blue to alternate locations around the Keys, she said. One of their more successful reintroductions took place at Bahia Honda State Park, the very area the species was rediscovered while on the brink of extinction.

From being laid as an egg to “dying of butterfly old age,” the Miami blue lives for about a month. Steele Cabrera said that the reintroduced population in Bahia Honda persisted for at least five to six generations, or around six months, without researcher interference. Unfortunately, it didn’t survive the winter and dry seasons — but that long-term survival is the researchers’ ultimate goal.

“It’s not like Jurassic Park where life finds a way — you put them there, and they’ll be fine,” she said. “It’s a whole lot more complicated than that.”

Could There be Future Flight on the Horizon?

If there’s anything to know about the future for the Miami blue, it’s that nothing is known for sure. But despite its uncertainty, ranger Killam said she is certain about one idea: It’s a species, a habitat and an ecosystem worth fighting for.

“The game’s not over yet. There’s time. We’ve still got the fourth quarter to go,” she said.

One way to combat the Miami blue’s uncertain future is to acknowledge the connection between their reproduction and rainfall events and recognize the pattern. Armed with this knowledge, Henry said she crafted population prediction models that take daily rainfall data into account when forecasting the butterfly’s future numbers.

But since rainfall fluctuates so much, it’s not as simple as plugging in the numbers and discovering if this species will survive the century’s end. Each climate model is greatly varied, she said, especially for South Florida — so a different outcome is expected depending on which prediction is used.

Even when looking at present populations, there are still questions that need to be answered, Henry said.

Some habitats seem perfect for the Miami blue, but there are no butterflies there. And in the places that there are productive populations, there are times that this elusive butterfly and its caterpillars will disappear for months. Henry said researchers know they’re there… but where are they, and what are they doing? “We really have no idea.”

“There’s still some of those big, just basic natural history gaps in our knowledge that makes it hard to pinpoint what conservation action we need to take,” she said. “We’re still working on some detective work to figure out what else is going on that we don’t quite know yet.”

The Miami blue, though only as big as a grape, shouldn’t fade into the past and join the growing list of extinct species, Steele Cabrera said. While it’s only a small link in an ecosystem’s chain, it still represents a piece of that chain that would be lost forever. And Florida’s biodiversity would shrink that much more.

It’s not just about the Miami blue, she said. It’s about every species at risk of becoming extinct.

“It’s a lot of insects and other organisms all over the world,” she said. “And so, we’re hoping by restoring populations of this one butterfly, we’re able to learn things that will help us restore populations or prevent extinctions of other, specifically, insects as well.”

This story is part of the UF Thompson Earth Systems Institute's student-produced Earth to Florida newsletter that curates the state’s environmental news and explains what’s going on, why it matters and what we can do about it.

The University of Florida Thompson Earth Systems Institute is advancing communication and education of Earth systems science in a way that inspires Floridians to be effective stewards of our planet.