At first, it seems like any other unboxing video on YouTube: A young man presents the viewer with a sealed box, expresses his excitement at what might be inside and peels away the packing tape.
But instead of pulling out a collectible toy or signature sneaker, he carefully unpacks seven live tarantulas, zooming in close enough to showcase the wispy bristles on their multijointed legs.
The tarantulas were the highlight of a mail-order spider “mystery box,” a biological grab bag that has become a popular offering in the thriving arachnid economy, much of which now exists, fittingly, on the web.
“You can buy yourself a mystery present of mystery spiders,” said Alice Hughes, a conservation biologist at the University of Hong Kong. “It’s like getting your deck of Pokémon cards: You might get a super rare one, or you might get a bunch of random stuff.”
In a new paper, published in Communications Biology on Thursday, Dr. Hughes and her colleagues shine a light on the largely unregulated trade of creatures that prefer to lurk in the dark. Their analysis of online sales listings turned up more than 1,200 species of spiders, scorpions and other arachnids; just 2 percent of them are subject to international trade regulations, the researchers report.
“Arachnids are being massively traded,” Dr. Hughes said. “And it seems to be going completely under the radar.”
Many organisms in the arachnid marketplace appear to have been caught in the wild rather than bred in captivity, the study found, and the ecological impact of their harvest remains unknown.
“They’re just being removed willy-nilly in large numbers,” said Anne Danielson-Francois, an arachnologist and behavioral ecologist at the University of Michigan-Dearborn who was not involved in the new research. She added, “They’re not this unlimited resource.”
Although the wildlife trade is a major threat to the planet’s fauna, regulation and public attention tends to focus primarily on well-known, charismatic animals, such as elephants, parrots and sea turtles.
But there’s a large and growing demand for invertebrates, experts said, and arachnids make popular pets. They are a cinch to ship — “You can literally mail an envelope of little spiderlings” Dr. Hughes said — and many species are relatively easy to care for.
“They don’t bark, they don’t need to go for walks — you can set up a simple arachnid in a five-gallon tank on your shelf,” said Ernest Cooper, an independent wildlife-trade expert in Canada. “They have fascinating behaviors. Some have bright colors.”
To learn more about the scale of the global arachnid trade, the authors of the new paper used a handful of search terms — “spider,” “scorpion,” “arachnid” — in nine languages to identify websites that might be selling the animals.
After eliminating shops selling spider excavators or Spider-Man collectibles, they scraped the data from the remaining sites to generate a list of arachnid species for sale online. (They also used the Internet Archive to find historical sales listings dating back to 2002.)
Across these sites, the study found a total of 1,248 arachnid species currently or previously for sale. The list included some showstoppers, such as the enormous Asian forest scorpion and striped Costa Rican zebra tarantula. But it also had some surprises, like Daddy longlegs spiders, common denizens of basements across America.
“They are literally balls with legs — small balls with legs,” said Caroline Fukushima, a postdoctoral researcher at the Finnish Museum of Natural History and an author of the paper. “You cannot impress someone with that.”
Compared with the expansive online listings, a U.S. Fish and Wildlife Service trade database included only 267 arachnid species, the scientists found. The Convention on International Trade in Endangered Species of Wild Fauna and Flora, or CITES, which regulates the international trade of a variety of plant and animal species, had just 30 species in its trade database.
(Individual nations may have their own regulations, and American authorities do sometimes intercept arachnids that arrive without the proper paperwork. Dr. Danielson-Francois was once the recipient of a box full of seized emperor scorpions that officials were seeking to unload.)
The online marketplace moves fast, with new arachnid species appearing in shops not long after they are first described by scientists. Nearly 200 of the species that have been discovered since 2000 are already being traded; dozens were available within a year or two of first being described, the researchers found.
“That suggests that people are going out to the field, and they’re finding something new and just collecting the heck out of it and then putting it up online for sale,” Dr. Danielson-Francois said.
Collectors may also be buying species that aren’t yet known to science. Dr. Hughes and her colleagues identified about 100 kinds of arachnids in trade that were consistently described as variants of known species, such as the “Vietnam blue tarantula.” (“Not for beginners,” the site Reptile Rapture cautions. “Very Defensive.”) But in many cases, these “variants” may actually be distinct new species, the scientists said.
In a separate analysis of the U.S. Fish and Wildlife records, the researchers found that about two-thirds of individual arachnids had been caught in the wild. Many were shipped from countries where they are not known to be native, suggesting that they may have been laundered across national borders, Dr. Hughes said.
The study has limitations. It is not an exhaustive inventory of every arachnid species available for purchase, and not all online listings may translate into actual sales, outside experts cautioned.
And the ecological effects of this trade are difficult to determine, in part because so little is known about arachnids. “We often don’t really fully understand the distributions of many of these species, let alone specifically where they occur, what they need to survive,” said Sarina Jepsen, who directs the endangered species program at the Xerces Society for Invertebrate Conservation, an international nonprofit.
But many arachnid species appear to be confined to small geographic regions; some, like tarantulas, mature slowly and have long life spans. “You can think of them as the rhinoceros or the panda of the arachnid world,” Dr. Danielson-Francois said. “It’s possible for local populations to go extinct when they’re poached.”
In another recent study, researchers at Cornell University found multiple species of endangered tarantulas being sold online.
Protecting arachnids will require more of everything, experts said: more regulation, more research on arachnid ecology and more data on precisely which species are being imported to and exported from specific countries — and in what quantities.
“Are there species that we should be particularly concerned about?” Dr. Cooper said. “Are there species that are hammered in large numbers every year? Every species is not equivalent.”
In the meantime, experts encouraged arachnid enthusiasts to do their homework before acquiring new organisms, making sure they know where the animals come from and whether they were captive-bred or wild-caught.
“We have to, as final consumers, think about what is our role in helping conservation of these animals that we love so much,” Dr. Fukushima said.