New softball-sized spider species discovered in Baja California Sur caves

A new species of large cave-dwelling spider, Califorctenus cacachilensis, has been discovered in Baja California Sur.
A new species of large cave-dwelling spider, Califorctenus cacachilensis, has been discovered in Baja California Sur. San Diego Natural History Museum

Goosebump alert.

Researchers at the San Diego Natural History Museum have discovered a new spider described as wide as a softball.

It’s crawling up your leg right now.


Michael Wall, Jim Berrian and other researchers found the large cave-dweller in the hills of Baja California Sur, Mexico.

“This is the type of spider that a lot of people would shriek and run from,” Wall told the Los Angeles Times.

It’s hairy and scary and has fangs. But Berrian waxed more romantic about their find.

“I think it’s a really pretty spider,” he told the Times. “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 determining that this really is a new species, they named it the Sierra Cacachilas wandering spider - Califorctenus Cacachilensis - after the Sierra Cacachilas mountain range where they found it.

Researchers from the San Diego museum have been making expeditions to remote regions of Baja to explore and catalog its flora and fauna, the Times reports.

The researchers unveiled the new spider - discovered with help from experts in Mexico and Brazil - last month in the journal Zootaxa.

They found it in 2013 during an expedition in a small mountain range outside of La Paz in Baja California Sur, Mexico.

“The first evidence we found of this species was a shed exoskeleton in the cracks of a rock overhang,” Berrian, a field entomologist, says in a museum blog post describing the discovery.

“The exoskeleton was abnormally big and I could tell by the eye pattern that it was in a group of spiders, wandering spiders from the Family Ctenidae, with very few species in Baja California Sur.”

They knew that wandering spiders are often nocturnal, so Berrian and his colleagues went back into the cave after dark. (Insert shudder here.)

When Maria Luisa Jimenez, an expert on Baja California Sur spiders, joined the expedition and saw the spiders, she was impressed by their size.

“In all my experience over the years collecting spiders on the peninsula, I had never seen a spider this large. I suspected that something new was waiting to be described,” said Jimenez, who works for the Centro de Investigaciones Biológicas del Noroeste in Mexico. points out that as super-sized as it seems, Cacachilensis and it’s puny 4-inch legs is much smaller than the giant huntsman spider, Heteropoda maxima, from Laos.

“Its legs can grow as large as 1 foot and it also stands accused of spinning webs out of nightmares and feasting on children’s dreams,” Smithsonian notes.

The question any arachnophobe would want to know: Is this new spider poisonous?

“They’re pretty meaty,” Wall told the Times. “They do have clearly visible fangs.”

“It’s intimidating, and that can be enough for a lot of things to leave you alone, except loony-toon arachnologists,” Berrian added.

Almost all spiders are venomous, but very few are dangerous to humans, Berrian said in the museum’s blog post.

“I got bit while handling a live specimen of Califorctenus Cacachilensis and I’m still alive,” he said. “We haven’t analyzed the toxicity of the venom, but most wandering spiders are not as dangerous as the Brazilian wandering spider.”

Finding a new spider isn’t all that unusual, considering that scientists have named about 1.1 million insect and spider species on the planet, with about 2 to 5 million still undescribed, the researchers said.

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