Texas is home to some of the creepiest, crawliest, and otherwise oddest animals on the planet. We introduce you to them in What in Tarnation?!, an occasional series.

More than three thousand caves lie beneath the Texas Hill Country. Today, scientists and spelunkers have explored and mapped most of them. That wasn’t the case in the late 1950s, when James Reddell, an English major at the University of Texas, joined the school’s speleological society and began crawling into caves after class and on weekends. He enjoyed the physical challenge of climbing and sliding through narrow passageways and labyrinthine tunnels with only the light of his headlamp, but what really thrilled him was the chance to see spaces and creatures that were virtually unknown. While explorers had been mapping land in Texas for centuries, and collecting and identifying plants and animals aboveground, caves were essentially a blank slate. Reddell was captivated by these hidden worlds, and he took every chance he got to explore caves across Texas and Mexico. He ultimately turned his passion into a career when he became the curator of cave invertebrates for UT’s insect collection, and for a time he was probably the only cave biologist in Texas.

Reddell had no shortage of fascinating species to study. Cave-dwelling creatures, also known as troglobites (not to be confused with their more adaptable cousins, the troglophiles), are exceedingly strange. While a portion of these critters are fish and amphibians, the majority are spiders, crustaceans, and other small, scuttling invertebrates. To live in total darkness, and without much food, they’ve had to evolve some pretty weird traits. Most troglobites are blind, pale, and sluggish. Some of these picky, hypersensitive species are so specialized that they can’t survive outside a specific cave, let alone in the sunshine. They’re the introverts of the underworld.

For several decades, Reddell collected critters he found in the caves, cataloged them, and occasionally sent them off for others to study and identify, slowly sorting the mysterious creatures into families and genera, and putting names to them. “We just look everywhere in the cave, turning over rocks and looking on the walls, floor, and ceiling, in pools,” Reddell says. “We grab whatever we can and put them in vials or jars and bring them back to the lab to sort them and send them out to specialists.” Reddell, now in his eighties, spent decades collecting tens of thousands of critters from more than a thousand caves in Texas and hundreds more in Mexico, New Mexico, and California. 

Thanks, in part, to the years of work Reddell and his colleagues put in underground, many of the species Reddell helped identify are now on the federal endangered species list. In fact, of the eleven endangered arachnids in the United States, nine are found only in Texas. These creepy crawlers live in Central Texas caves within the Balcones Escarpment, a narrow fault zone that runs along the eastern edge of the Edwards Plateau, where wooded hills dip off into the coastal plains.

One of the rare species that Reddell was the first to collect in the 1960s is a blind, long-legged, spiderlike arachnid called the Bone Cave harvestman. In recent years, this little creature was at the center of a big controversy, one that almost went all the way to the U.S. Supreme Court and that threatened not just this specific critter, but 70 percent of all imperiled animals protected by the Endangered Species Act. On December 28, the saga ended with a rare win for environmentalists: the U.S. Fish and Wildlife Service announced that the Bone Cave harvestman would stay on the endangered species list.

We’ll get to the politics in a moment, but first, what the heck is a Bone Cave harvestman? It looks like a lot like a spider, but it isn’t one. The peppercorn-sized creature (it tops out at 0.1 inches long) is a light orange version of the daddy longlegs you’ve probably seen aboveground. (“Daddy longlegs” is a nickname for harvestmen that highlights their exceedingly long appendages, which are well adapted to moving quickly along cave walls.) While spiders have distinct heads, harvestmen are distinguished mostly by their single fused head and body. Harvestmen also lack venom glands and spinnerets for spinning webs. 

The Bone Cave harvestman lives only in subterranean habitats, mostly in tight crevices and beneath rocks, though it’s occasionally spotted scurrying across a cave floor or wall. Because it’s so rare and is only found underground, relatively little is known about this species. It’s probable that, like other harvestmen, it’s both a scavenger and a predator. It may eat decaying organic matter, larvae, and even tinier cave critters, such as collembolans. Likewise, harvestmen are probably meals for cave spiders, scorpions, and centipedes. An individual can live up to four years, maybe longer.

Bone Cave Harvestman spider
The Bone Cave harvestman.Colin Strickland/City of Austin

The Bone Cave harvestman has likely been in Texas since before the last ice age. Experts suspect that two distinct species evolved from a common ancestor and scuttled about aboveground before a climatic change drove them underground. Studies show that the critters at the northernmost extent of their range, in Williamson County, likely went underground sooner and adapted more fully to cave life, developing longer legs and lighter pigmentation. When the Colorado River cut through the geologic layers in Central Texas, it likely created a barrier, and the two species adapted to cave life at different rates on either side. Today, the Bone Cave harvestman is found north of the river, and its cousin, the Bee Creek cave harvestman, dwells south of the river.

Until the early nineties, these and several other distinct arachnids were considered the same species: Texella reddelli. The name is a nod to Reddell, the intrepid Texan who first collected the animals. (There are now 51 species named in his honor.) In 1992, Darrell Ubick and Thomas Briggs, taxonomists at the California Academy of Sciences, examined harvestmen that Reddell and his team had collected and recognized that what was previously thought to be a single species was actually more. Thanks to their painstaking work, the Bone Cave harvestman was identified for the first time as its own species. The common name refers to where Reddell and his team found the critter. Its scientific name is Texella reyesi, in honor of Marcelino Reyes, Reddell’s longtime assistant and caving buddy. He was part of the team that collected the specimen at Bone Cave in Williamson County.

Now we’re getting to the political part of the story. In 1988, as development and population growth led to habitat loss in Central Texas, USFWS added the harvestman to the endangered species list. Ever since, there’s been a dizzying array of bureaucratic and legal efforts to strip the humble invertebrate of its federal protection. This isn’t because anyone has a vendetta against the harvestman—though its lack of charisma certainly doesn’t help—but rather because developing around an endangered species is a pain. If you want to put houses or commercial buildings on your land, for example, you have to dig down to construct the foundation—and doing that, or paving over a once permeable green space, in the wrong spot can disrupt the delicate ecosystem where these animals thrive. Following the law can mean more red tape for landowners, though the Endangered Species Act doesn’t forbid development near a harvestman habitat. “It is a misconception that if a species is listed, it stops development,” says Michael Warriner, a supervisory biologist with USFWS. “There are a number of avenues for someone to still develop a property.” Nonetheless, landowners who knowingly disturb an endangered habitat could be subject to serious fines or even imprisonment.

In 1993, a Williamson County judge filed the first petition to delist the harvestman and six other invertebrates. Then in 2014, a group that included Georgetown property owners and a conservative private property–rights organization petitioned USFWS to delist the species. The agency initially held firm, but the petitioners took the case to federal district court, where a judge ruled that the service needed to reevaluate the endangered species listing. Texas attorney general Ken Paxton lauded the ruling, saying “The court’s decision is a victory for private property rights in Texas and a defeat for an unlawful Obama-era land grab.” In 2019, under the Trump administration, the USFWS changed course, decided that delisting the Bone Cave harvestman might be warranted, and initiated a more detailed review.

Then the state’s most powerful right-wing think tank joined the fray. The Texas Public Policy Foundation launched a constitutional challenge (ardently supported by Paxton) to the Endangered Species Act. TPPF argued that the federal government didn’t have the authority to protect the harvestman because it’s found only in Texas. Now the debate wasn’t just about the harvestman, but also about the roughly 70 percent of endangered species that live only in one state. All of them could lose protections if TPPF were to win. The debate wended its way through the courts for more than five years—and eventually the environmentalists won. The district court rejected the constitutional challenge, the Fifth Circuit dismissed an appeal, and in 2021, the U.S. Supreme Court declined to hear the case. “We’re glad this attack on the Endangered Species Act’s constitutionality will go no further,” an attorney with the Center for Biological Diversity said at the time. The recent decision to maintain the endangered status may have finally put the issue to bed, at least for the moment. 

Reddell wasn’t surprised by the decision, but he welcomed it. Many of the caves he explored back in the sixties have been completely destroyed as urban sprawl has spread out of Austin. “If it hadn’t been for the Endangered Species Act, there wouldn’t be very many caves left in Central Texas,” he says. In fact, the Bone Cave harvestman and its kin may be among the few obstacles that still stand in the way of widespread destruction of cave ecosystems, and the green space above.

“People say, ‘Why are we worrying about all these bugs?’ Well, the fact is we’re worrying about our way of life,” Reddell says. “You can’t tell me a developer is going to go broke because he set a few acres aside for bugs.”