The strike maneuvers of flattie spiders are the fastest documented turn of any terrestrial animal that relies on legs.
The combination of speed and deception that make the flattie spider one of the most feared predators in the insect world could serve as inspiration for the next generation of multi-legged robots.
Researchers from the University of California Merced and the California Academy of Sciences have documented how individuals from the spider family Selenopidae—commonly called flattie spiders—can sense prey approaching from any direction and whip around in just one-eighth of a second to strike.
“We are documenting and modeling their fast spins, to help chart a course for making robots and other machines more maneuverable,” lead author Yu Zeng, PhD., of UC Merced, said in a statement.
The team found through high-speed footage that a swift flex of the flattie spider’s long legs helps them accomplish the quick strike attack, which is considered the fastest leg-driven turn of any animal on the planet at up to 3,000 degrees per second. The researchers were able to capture the high-speed insect with two synchronized, high-speed video cameras above and beside the spider. The researchers then examined strike footage at speeds roughly 40 times slower than the original to map the mechanics of spiders.The researchers discovered that the outward stance tracks parallel to the ground, allowing for a wider range of unrestricted motion.
Each leg also faces a separate direction and thereby covers a different slice of their 360-degree surroundings. This allows the spider to spin to orient itself toward unsuspecting prey regardless of the angle of the approach.
“Only about half of all spiders use webs to catch prey,” Sarah Crews, PhD, a postdoctoral researcher at the California Academy of Sciences, said in a statement. “Some stalk and pounce, while others are sit-and-wait ambushers–like flattie spiders.”
While flattie spiders have eight eyes, it is unknown whether they are used for vision. However, it is known that they detect approaching prey through disturbances in air current, including hopping crickets and buzzing fruit flies.
The researchers simulated the ambush of the perceptive sit-and-wait predators for each trial by releasing a cricket and allowing it to walk freely toward the spider.
“We found that the leg nearest the prey anchors to the ground, creating a leverage point from which the spider can pull in its torso closer to the prey,” Zeng said.
Zeng explained that legs opposite the prey push off the ground to assist, enabling the beginning of a twisting force that propels the spider into a swift spin. The spiders then pull their remaining legs in and off the ground, holding them close and allowing them to spin up to 40 percent faster and land perfectly positioned with their mouth towards the first bite of prey.
Flattie spiders can be found across North and South America as well as Africa, Asia, and Australia, often in tree and rock surfaces.
“Flattie spiders are always one step ahead in this evolutionary arms race between predator and prey,” Crews said. “If the prey are positioned further away, spiders move faster both linearly and with increasing rotational speeds–there’s truly no escape.”
