Saucer-sized spider discovered in Baja cave

In the hills of Baja, Michael Wall and Jim Berrian found a creature that’s the stuff of nightmare for most people — a cave spider nearly the size of a tarantula.

For the two San Diego Natural History Museum researchers, it was an exciting windfall — an unknown arachnid as wide across as a softball.

“This is the type of spider that a lot of people would shriek and run from — it’s big enough to fall in that category,” said Wall, curator of entomology for the museum.

The brand new species has the stuff of horror films: eight beady eyes, thick fang-like structures, a hairy, inch-long body and legs stretching four inches wide. Berrian, however, describes it in more flattering terms.

“I think it’s a really pretty spider,” he said. “The head and legs are kind of a chocolate brown. The abdomen is a dull yellow. And it’s kind of plain, but very striking.”

After confirming the spider as a new species, they named it Califorctenus cacachilensis after the Sierra Cacachilas mountain range where they found it, and published the discovery in the journal Zootaxa last month.

There are 1.1 million species of insects and spiders that have been scientifically described, but an estimated four million species are yet to be identified and named, Wall said. So encountering a new type of spider isn’t necessarily unusual.

“The odds of discovering a new species are pretty high,” Wall said. “But that said, generally, (most) new species discovered are little itty-bitty things that people don’t pay attention to, so given the size of this spider, that was surprising.”

Berrian first saw shed exoskeletons of the species in a grotto in the Cacachilas during a 2013 expedition, and was on the lookout for the live thing. Soon he and Wall found one in a nearby cave, and another in an abandoned mine shaft. Local ranchers with broad knowledge of the area’s wildlife hadn’t seen it before, but the researchers kept searching. They spotted more of them in the cement pit of old outhouse and others in secluded crevices.

“Once we knew that they were in these dark, reclusive places, we started targeting those and ended up finding more of them,” Wall said.

They located about two dozen of them, Berrian said, and brought back about eight specimens. Convinced that the spider was unlike others in the area, but unsure what it was, they consulted Mexican entomologist Maria Jimenez to nail down its taxonomy. She concluded that the new species belongs to the family of wandering spiders, which includes the Brazilian wandering spider, known for its potent and sometimes lethal venom. Cacachilensis looks like it could wield an impressive bite as well.

“They’re pretty meaty,” Wall said. “They do have clearly visible fangs. You don’t have to look very hard to find them.”

Under rows of black eyes, the spider has thick, hairy pincers that can deliver a venomous sting. That’s how the wandering spiders, named for their habit of roaming for prey, hunt for food and defend themselves against other animals.

“It’s intimidating, and that can be enough for a lot of things to leave you alone, except loony-tune arachnologists,” Berrian said, acknowledging that it wasn’t enough to deter him from handling the spiders.

Unlike its Brazilian cousin, he discovered, cacachilensis doesn’t seem to kill you.

“I was bitten by one of these spiders down in Baja,” he said, describing it as milder than a bee or wasp sting. “It was like being poked by a cactus spine and a little mild pain, but it went away in a few hours.”

The spider’s discovery came during a series of expeditions by researchers at the San Diego Natural History Museum to explore and catalogue the flora and fauna of remote regions of Baja. They believe the species is unique — or endemic — to certain areas of the Baja Peninsula. So that makes it an important find in terms of research and conservation of the region.

“This spider has a very small range,” Berrian said. “Along with other endemics — birds and reptiles — altogether, it tells a story of the uniqueness of that area. And we can use that to justify protection.”

deborah.brennan@sduniontribune.com Twitter@deborahsbrennan