When this spider senses its prey approaching from any direction, it can turn to strike faster than a blink of an eye, taking just one-eighth of a second to make its spin.
Researchers from the University of California Merced and the California Academy of Sciences have found that flattie spiders — from the spider family Selenopidae — make the fastest leg-driven turn of any land animal on the planet. Their findings were published this week in the Journal of Experimental Biology.
According to a press release from the California Academy of Sciences on the research, flattie spiders turn to strike their prey at speeds of up to 3,000 degrees per second. Moving at full speed, they can even make three complete rotations in the time it takes to blink your eye. They rank among the fastest-turning animals, along with hummingbirds and fruit flies.
"About half of all spiders species don't use webs to catch prey," Sarah Crews, an expert on the Selenopidae family and a postdoctoral researcher at the Academy, says in the press release. "Some stalk and pounce, while others are sit-and-wait ambushers—like flattie spiders."
Crews, an author of the new study, searched field sites to locate the spiders, which linger on trees and rocky surfaces, to take back to the lab. The spiders are nocturnal, so the entire collection process all had to be done in the dark. They can be found across North and South America as well as Africa, Asia and Australia.
Because their swift skills aren’t visible to the naked eye, Crews and lead author Yu Zeng of UC Merced positioned two synchronized, high-speed video cameras above and beside the spiders to capture the action. Then, for each trial, they released a cricket and allowed it to walk toward the spider. They slowed down footage about 40 times the original to examine the mechanics behind the spiders’ hunting strike.
This revealed how they’re able to use their long legs to catch prey. The leg closest the prey is used as an anchor in the ground, allowing the spider to pull its body toward its prey. The legs opposite the prey simultaneously push off the ground to help. This combination achieves a twisting force that launches the spider into its spin.
And though spiders have eight eyes, researchers still don’t know if they are actually used for seeing. Instead, researchers believe that flattie spiders can sense prey approaching by changes in air current.
"Flattie spiders are always one step ahead in this evolutionary arms race between predator and prey," Crews said in the press release. "If the prey are positioned further away, spiders move faster both linearly and with increasing rotational speeds—there's truly no escape."
The researchers believe their finding also has practical applications; they hope the spider’s turn can inform technology and innovation. "We are documenting and modeling their fast spins," Zeng says in the release, "to help chart a course for making robots and other machines more maneuverable."
For example, the latest find could influence how robots move in search-and-rescue missions, Alper Bozkurt, associate professor of electrical and computer engineering at North Carolina State University, tells Smithsonian.com. “The discovery of new features in insects always excite us engineers as we continuously try to learn from these tiny living machines when we are designing our synthetic robotic ones,” he says. “The coordination of the spiders to implement the observed quick maneuver is fascinating and mind blowing, and is a result of an interplay between sensory organs, neural circuitry and biomechanical actuators. Being able to replicate such a maneuver on robots would enable new capabilities in machines used in search and rescue, transportation as well as space missions.”
As Elaina Zachos, reports for National Geographic, one bio-inspired robot that has a 3-D printed shell and eight spider-like legs already exists. It has individual motors to help the machine move. This latest research could eventually help similar spider-like robots twirl with incredible speed.