Love a good mystery? Here’s one about a tiny West Texas spider that for years baffled experts and amazed them, too. Throw in some fierce ants for added drama, and you’ve got a riveting read that made spider history.
The saga begins in 1999 when Greg Broussard, a graduate student at Midwestern State University, couldn’t identify a spider he’d collected at MSU’s Dalquest Desert Research Station, which adjoins Big Bend Ranch State Park. Back on campus, Broussard asked his professor for help.
“After several days, I was stumped,” says Norman Horner, now a professor emeritus of biology and former director of MSU’s Natural Laboratories.
From there, the “Texas mystery spider,” as the specimen came to be known, was passed from one expert to another. No one could identify it. In New York City, Norman Platnick, a top spider specialist at the American Museum of Natural History, scoffed after he examined the caramel-colored arachnid, a bit bigger than a flea.
“He said the spider did not come from North America,” Horner recalls. “We assured him that it did.”
Intrigued, Platnick organized a search party funded by the museum. The group spent a week at the research center but trapped only one spider.
Meanwhile, in 2008, David Lightfoot of the Museum of Southwestern Biology at the University of New Mexico observed some tiny spiders on the surface of harvester ant nests in the desert near Cuatro Ciénegas in Mexico. When specimens reached Platnick, he recognized them as the same mystery spider. Researchers now had a clue where to find more – ant beds in the Chihuahuan Desert.
Under the microscope, further investigations on specimens revealed unique molecular and anatomical characteristics. In 2019 the Texas mystery spider was described as not only a new species, Myrmecicultor chihuahuensis, but so evolutionarily unique that it is the first member of an entirely new spider family, Myrmecicultoridae.
Ironically, the new spider doesn’t quite fit its name. In Greek, “myrmex” means “ant”; a Latin translation of “cultor” is “worshipper.” Not so in this case, according to recent discoveries made by Paula Cushing with the Denver Museum of Nature and Science. Her video and photographic evidence indicates that M. chihuahuensis lives within the nests of harvester ants. It also hunts them in a surprising way outside the nest.
“Most predators avoid ants because they bite, sting and attack,” says Cushing, an evolutionary biologist who researches spiders associated with ants. “Some have evolved specialized strategies to avoid those dangers. These spiders rush up to an ant, bite a rear leg, back off and wait for the venom to take effect, then lift the paralyzed ant away to feed.”
Here’s the amazing surprise: “If a live ant approaches,” Cushing continues, “then the spider twists its body and presents the dead ant as a shield.” (Similar “shielding” behavior has been observed only in the spider genus of Zodarion.)
Now that the mystery’s solved, what’s next? This fall, Cushing, Horner and other researchers plan to return to the Chihuahuan Desert to document the spiders emerging from harvester ant nests and stalking ants. “We would love to see that action sequence,” she says.
