A version of this story appears in the October 2019 issue of National Geographic magazine.

The world’s largest bee may also be the planet’s most elusive. First discovered in 1859 by the prominent scientist Alfred Russel Wallace, researchers could not locate it again, and it was presumed extinct.

But Wallace’s giant bee (Megachile pluto) was not gone. In 1981, an entomologist named Adam Messer searched and found it on three islands in Indonesia, on an archipelago called the North Moluccas. He collected a specimen and wrote about his discovery in 1984.

Now, for the first time, it has been photographed and filmed alive in the wild, by a team including nature photographer Clay Bolt. Meanwhile, in the last year, two specimens of the insect have been sold on eBay for thousands of dollars, raising fears about its continued survival.

The bee, which grows up to an inch and a half long with a wingspan of 2.5 inches, has large mandibles that almost look like those of a stag beetle. It uses them to scrape sticky resin off trees to build burrows within termite nests, where females raise their young. Like other bees, it feeds on nectar and pollen.

Messer wrote in 1984 that it remains rare in its range, and as this solitary bee lives only in aerial termite mounds, it isn’t exactly easy to find. It was collected in 1991 by a French researcher, though not filmed or photographed at that time.

View Images Female bees collect tree resin with their mandibles and use it to build burrows within arboreal termite nests, where they raise their young. PHOTOGRAPH BY Clay Bolt

Bolt and trip member Eli Wyman, a biologist at Princeton, were overjoyed to find the bee on an expedition in January. One of the most notable things about the bee, a female, was the sound of her wings: a “deep, slow thrum that you could almost feel as well as hear,” Bolt says.

Wyman says he could feel the displacement of air as she flew by. “Such an incredible, tangible experience from an animal that had only lived in my imagination for years,” he adds.

View Images The original specimen of Wallace's giant bee, collected by Alfred Russel Wallace. Photograph by Robert Clark, Nat Geo Image Collection

Many have become intrigued by the insect, including Nicolas Vereecken, an entomologist and ecologist at the University of Brussels. He studies bee diversity and was naturally interested to see the world’s largest. Over a decade ago, he sought out a specimen collected by Wallace himself, housed at Oxford Natural History Museum.

That only made him want to learn more. Early last year, at Naturalis Biodiversity Center in the Netherlands, he stumbled across a specimen collected in 1991 by a French researcher named Roch Desmier de Chenon. (The man was thought to be dead by many in France, but Vereecken found to his surprise and joy that de Chenon is alive, and living in Melbourne, Australia.)

The very same day, Vereecken discovered that a collector was selling a specimen of Megachile pluto online, on eBay—it eventually sold for $9,100. Later in 2018, the same collector sold another for a couple thousand dollars. The bee, it seemed, was very much still around.

Vereecken is alarmed that this insect has been sold online—and it’s possible that more commerce is taking place through less visible channels. He described these sales in a study published in December in the Journal of Insect Conservation.

It’s currently legal for this species to be sold across borders, as the animal is not protected by the Convention on International Trade in Endangered Species, which governs international trade in threatened species. Wallace’s giant bee is currently only considered “vulnerable” by the International Union for Conservation of Nature, which sets the conservation statuses of animals around the world. Vereecken and others think it should be classified as endangered, at the very least, considering how rare it is and that its range is almost certainly smaller than originally thought. Vereecken is pushing to change its status, though doing so will require more study.

Wallace's giant bee is also threatened by deforestation and habitat loss. The report of the discovery comes shortly after the publication of a worldwide study showing that insect species are in decline around the world.

Bolt traveled to Indonesia with Wyman, Australian biologist Simon Robson, and writer Glen Chilton in January. After five days of fruitlessly searching termite mounds in trees during the rainy season, the team had begun to feel a bit discouraged. They were about to call it a day, Bolt says, when they searched one last nest—which had a resiny hole within.

After several members of the party climbed up to take a took, it became clear there was a bee in the hole. They put a collection tube at the exit, and a full-sized female Wallace’s giant bee crawled out.

“We yelled and screamed and hugged each other,” Robson says. After photographing and filming it, they let it go and it returned to the nest. Unlike some of its relatives, the bee seemed “very relaxed” and non-aggressive, Bolt adds.

Roch Desmier de Chenon, who is now 80, was working for the Indonesian Oil Palm Research Institute in 1991 when he decided to search for Wallace's giant bee on the island of Halmahera. Locals, some of whom were familiar with the bee, guided him to a particular tree where the insects collect sap. He says over the course of his research he saw about 20 to 30 of the giants, though he only collected one.

"I was very happy to find it because I knew it was a big discovery," de Chenon says, but he didn't publish his work, in part because he feared that collectors would use the information for nefarious purposes. He now regrets not publishing his finding.

Indeed, on the one hand, publicizing the discovery of the insect could seem like a risk, considering that it has been sold online, says Robin Moore, with Global Wildlife Conservation, which helped organize the trip. But in reality, unscrupulous collectors already know that it exists.

Thus, promoting its discovery and specialness could help the local government and various stakeholders get behind its protection.

“If we don’t do anything, it [may] just be collected and slip into obscurity,” Bolt says.