Philadelphia has a mysterious critter found nowhere else. Meet the volunteers tracking it.

Her other options exhausted, Sonia Jung reached for the self-closing forceps. Neither the reed of grass, the cotton swab, nor the nylon foam had been enough to lure one of Philadelphia’s most secretive animals.

Carefully, she grasped the small, bright green bait, and brushed it against a mottled root that reached up from the ground and onto a nearby wooden post.

“I don’t think I was planning this morning to come and dangle a grasshopper on a spider web,” she said with a laugh.

Jung is an engineer, recently displaced from her former job at Philadelphia Energy Solutions by the explosion and subsequent closure of the company’s refinery in South Philly. But she also is part of a small team of dedicated volunteers. Together, they are studying an animal that cannot be found anywhere else in the world: Atypus snetsingeri, the Pennsylvanian purseweb spider.

Some of Philadelphia’s spiders — like the large but harmless orbweavers at the Spring Garden SEPTA station — are hard to miss. The Pennsylvanian purseweb can also be quite striking, say the lucky few who have seen one.

Built like inch-long tarantulas and painted in earth tones, the spider’s shiny exoskeleton gleams in the right light. Although a little different from true tarantulas, the pursewebs are closely related. They seem exotic; something one might find in a documentary, not along Cobbs Creek in West Philly.

But, of course, that’s because “no one ever sees them," explained Steve Tessler, a volunteer naturalist at Tyler Arboretum. He is also the world’s leading expert on the Pennsylvania purseweb spider.

“They are very secretive. ... They live their entire lives in their tube,” he said, referring to the silken, tunnel-shaped webs from which pursewebs get their name — when similar spiders were first described in 1792, many “purses” were long, socklike pouches.

Ever the introvert, the purseweb spider refuses to leave its home even to eat. “So, the way it hunts, when something walks on the tube, the spider comes up from the inside, stabs through [the tunnel’s wall] with its fangs and drags [the prey] in," said Tessler. Only adult males ever leave their web, to find mates.

And thanks to the spider’s skills at decoration, its web is essentially unrecognizable to the untrained eye. Tessler enjoys pointing out the rootlike web to new volunteers for the first time — he is often met with an incredulous “That’s a spider web!?”

As a result of its reclusive nature, the Pennsylvanian purseweb has gone largely unnoticed by its fellow Philadelphians, despite being intrinsically tied to the region and its inhabitants.

For countless years, it lived quietly and unobtrusively alongside people. Then, in 1969, a resident of Landsdowne Avenue, in what is now Upper Darby, Delaware County, found a strange creature in the backyard. Three years later, Patricia Sarno, then working on a master’s degree in biology at Pennsylvania State University, published a paper describing the new species. While she found many of the spiders living at the base of hedgerows and trees, she reported that some of the first she encountered were in a residential swimming-pool filter.

While the purseweb has relatives in Europe and Asia, Sarno discovered that the Pennsylvanian purseweb was special — it was (and still is) the only known species of Atypus spiders in all of the Americas.

Sarno named the spider Atypus snetsingeri after her mentor, Bob Snetsinger, a professor of entomology at Penn State. A lover of arthropods, Snetsinger would later be known as “Butterfly Bob” for his work to build butterfly gardens across central Pennsylvania.

Steve Tessler was the next to meet the spider. As an undergraduate at Penn State, Tessler was hired by Snetsinger to manage the university’s collection of preserved spiders. He didn’t plan to study the Pennsylvanian purseweb at first, but spotting their webs slowly became a personal hobby. He found a population of the spider at Naylors Run Park, down the hill from his former high school. There, Tessler collected several spiders and described their habitat, sending his findings to famous arachnologist Norman Platnick, who wrote a 1980 paper about Atypus purseweb spiders.

And, except for brief references to its existence, that is where the Pennsylvanian purseweb’s story ended.

Tessler completed graduate school, and began a successful career in public service, first at the National Park Service, and then with the U.S. Geological Survey. Sarno returned to Schuylkill County, her childhood home. There, she shared her passion for nature as a science teacher at Schuylkill Haven High School, where she taught for 37 years, as reported by her 2006 obituary. And while Snetsinger remained at Penn State until his retirement in 1999, he does not appear to have continued research on his namesake.

But Tessler never forgot about the strange spiders in his childhood neighborhood. “I lived away [from Philadelphia] for 25 years. And when I came back visiting family, I would take a day and go here and go there, and see whether I find [the spider] or not,” he said.

Tessler worked alone for many years, but eventually realized that to make more progress, he needed help. Earlier this year, he started the Tyler Arboretum Spider Watch, a group of volunteers dedicated to studying the Pennsylvanian purseweb spider. Their first goal was to discover when and how the babies, called spiderlings, know to emerge en masse from their mother’s burrow.

While team members will need more years’ worth of data to predict the spiderlings’ emergence, they have discovered that instead of “ballooning” into the sky, as many other spiders do, the pursewebs “swing," much like Spider-Man. The babies climb to the top of a stem, attach a strand of web, then jump off, letting the wind swing forward and out, on a trajectory to the next plant.

“You’re probably wondering, y’know, why would people choose to volunteer with spiders?” said Julia Lo Ehrhardt, the community outreach manager at Tyler Arboretum. She points to the spider’s mystery as a major draw.

“There were some [people] that were so curious, they were willing to lay on their bellies, and look into holes to see these spiders, rain or shine," she said. Ehrhardt welcomes anyone who is interested to visit Tyler Arboretum and register as a volunteer.

For some of the team, meeting the Pennsylvanian purseweb has been transformative.

“I didn’t know much about spiders,” said Sue Lucas, a current Spider Watch volunteer. “I was afraid of them for a long time. The first [purseweb] I met was a baby ... and that was really exciting. They are actually gentle.”

The Spider Watch’s new project seeks to coax the reclusive spiders out of their burrows so they can be safely observed and measured. The alternative is to dig out the delicate spider, which even for Tessler is a long process with only about a 25% success rate.

So far, a grasshopper walking on the spider’s web seems to be the most convincing bait, although Tessler continues to work on his technique with the reed of grass.

So much remains unknown about the Pennsylvanian purseweb that one of Tessler’s other ongoing questions is simple: Where, exactly, does the spider live?

According to the scientific record, they are only in Delaware County. But Tessler and his volunteers have spotted pursewebs by Cobbs Creek, in Fairmount Park, at Heinz Wildlife Refuge, and possibly as far north as Valley Forge.

“I’m pretty convinced that they could even be in Center City," Tessler said.

To track down new populations of the Pennsylvanian purseweb, Tessler has developed a way for all Philadelphians to be part of the Spider Watch. Using the “Map the Spider” project on the community science app EpiCollect5, anyone can look for the spider’s unique webs and upload the findings.

Tessler hopes that the search for our unique spider will open people’s eyes to a new facet of Philly life. “I’ve always been interested in trying to show people that they don’t have to go to exotic places to see really exotic things — they’re right at your feet," he said.