A Poecilotheria fasciata in Sri Lanka blickwinkel/Alamy

Eight legs. Eight eyes. Sixteen claws. Two fangs. And about a bajillion dark, bristly guard hairs. Mere images of tarantulas can send shivers down the spine, and it’s little wonder that these lanky arthropods hang beside cardboard ghosts and goblins to make trick-or-treaters jump.

But behind their menacing appearance, tarantulas are just one more animal trying to hack it in the real world.

“Like all spiders, tarantulas have an important job on earth,” says Karen Verderame, an invertebrate specialist at Drexel University. “They’re exterminating for free, and despite how they’re depicted in movies or at Halloween time, they are good spiders to have.”

Worldwide, spiders capture between 400 and 800 million tons of insects and other critters each year. The dent they make in mosquito populations alone is good enough reason to think twice before you squish.

And speaking of second chances, the U.S. Fish and Wildlife Service recently granted Endangered Species Act protections to five species of tarantula from Sri Lanka. All of these tarantulas, known as tiger spiders, are listed as “endangered.” With just 150 individuals found during recent surveys, Poecilotheria fasciata, from the northern part of the island, is the most abundant of the bunch. Poecilotheria smithi isn’t even as lucky as that. The scientists found only 16 of them in their native central highlands.

How many of the arachnids once roamed the island is unknown, as is how big their home ranges once were, but the researchers agree that all five tiger spiders are in decline. In fact, a 2013 study gave these creepers just two to three decades before going extinct.

Deforestation is the main bogeyman here. The tiger tarantulas live in trees, where they wait in crevices to pounce upon lunch—a small bird, a rodent, perhaps a snake—as it wanders by. Unfortunately, between 1990 and 2005, Sri Lanka cut down 17.7 percent of its forests—more than a million acres.

Another threat, to the surprise of no one, is extermination. Many Sri Lankans feel the same way about tarantulas as Marv from Home Alone. When the body of an arachnid is as big as a credit card and its legs can stretch out long enough to cover someone’s face, it tends to inspire violence.

A tiger spider’s behavior doesn’t help. Tree-loving tarantulas are freaky fast and more on edge than ground-dwelling, New World tarantulas. Verderame says this is partly because Old World species, like those in Sri Lanka, lack the ability to kick up a cloud of urticating hairs when attacked by predators. The hairs clog and irritate the mucous membranes of attackers’ eyes, noses, and throats, which can help the tarantulas escape. Without such defenses, Old World spideys “tend to be more aggressive, quicker to bite, also just faster in their takeoff,” Verderame says.

That’s right. These huge spiders have fangs and aren’t afraid to use them. And although the venomous bite of a Sri Lankan tarantula isn’t fatal to humans, it does hurt like the dickens and can cause extended muscle cramps. As a result, loggers and villagers are known to squash the spiders on sight.

Such killings further harm populations that are already grappling with habitat destruction from logging and mining, says the FWS. But they also prevent wandering males and dispersing juveniles from colonizing new territories or contributing genetic diversity to neighboring populations.

And then there’s the pet trade. Despite their terrifying size and terrible personality, tarantulas from this family have been popular pets for at least 30 years. Verderame says it’s because they’re so darn pretty (it’s in the eye of the beholder, remember).

Poecilotheria metallica, seen from underneath Wildlife Gmbh/Alamy

“The undersides of their legs are almost iridescent; they have a sheen to them,” she says. When feeling threatened, tiger spiders rear up and flash all those fancy hairs, which reflect light in a way that startles or distracts their enemies long enough for the spiders to attack or speed away. This trick, of course, can also make them a handful for unwitting pet owners.

“This isn’t a beginner’s tarantula,” says Verderame. No kidding.

Even though most pet tiger spiders are captive-bred, trapping tiger spiders in the wild for the pet trade is not unheard of. And with population numbers as low as they are, every tarantula counts. The newly acquired ESA designation makes it illegal to import wild-caught tiger spiders into the United States. The endangered status helps these creepy-crawlies in other ways, too—and importantly, on their own turf.

“Listing encourages increased awareness of the species, research efforts to address conservation needs, and funding for conservation in range countries,” says Taylor Jones, an endangered species advocate with WildEarth Guardians, which originally petitioned the FWS to list the tarantulas in 2010.

A place on the Endangered Species List also gives the FWS the option to dedicate funding and expertise to any number of programs abroad, from helping Sri Lanka set up better management practices to training law enforcement officers. It should be noted, however, that while an endangered status makes such resource allocations possible, it does not mandate them. And considering the Trump administration’s attacks on the Endangered Species Act itself, well . . . let’s say the chances of Sri Lankan tarantulas getting special treatment is as slight as a strand of spiderweb. Still, as it stands now, the bar is pretty low. The FWS found no evidence of any tiger spider–targeted conservation programs in Sri Lanka, which means almost anything would help at this point.

Sri Lanka’s Forest Department announced in 2016 that it plans to increase forest cover from 24 percent to 35 percent by 2020. This is another step in the right direction, because in the end, the fates of these tremendous tarantulas are inextricably bound to the trees they inhabit: more crevices to lurk in, more branches to pounce from, and more prey to sink their fangs into.

onEarth provides reporting and analysis about environmental science, policy, and culture. All opinions expressed are those of the authors and do not necessarily reflect the policies or positions of NRDC. Learn more or follow us on Facebook and Twitter.