Natures wonders: 'fastest spin' flattie spiders (Introduction)

by David Turell , Monday, February 12, 2018, 17:27 (2474 days ago) @ David Turell

The timed spin is the fastest measured. These spiders don't use webs. They stalk and spin:

https://phys.org/news/2018-02-fastest-earth-animals-legs-scientists.html

"There's no sneaking by this spider. New research from the University of California Merced and the California Academy of Sciences shows that individuals from the spider family Selenopidae—commonly known as flattie spiders—can sense prey approaching from any direction and whip around in one-eighth of a second to strike. High-speed footage reveals that a swift flex of their long legs helps the hunters accomplish this feat, deemed the fastest leg-driven turn of any animal on the planet.

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"What makes flattie spiders ready to spin on a dime? It's all in the legs: Their 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 365-degree surroundings. This means the spider can spin to orient itself toward unsuspecting prey no matter the angle of approach.

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"Flattie spiders keep watchful eyes out—eight to be exact—for their next victim, although it's still not known if any are actually used for seeing. Instead the spiders detect approaching prey, like hopping crickets or buzzing fruit flies, through disturbances in air current.

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"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," says Zeng, describing the spider's linear lunge. Legs opposite the prey push off the ground to assist. Together, this combination of pull and push also provides the beginnings of a twisting force—known as torque—that propels the spider into a swift spin.

"Like figure skaters drawing their arms inward to spin faster, flattie spiders then pull their remaining legs in off the ground, holding them close. This allows the graceful hunters to spin up to 40% faster and land perfectly positioned with their mouth towards that first bite of prey.

"Around the globe, flattie spiders are turning to strike their prey at speeds of up to 3,000 degrees per second. In the time it takes you to blink your eyes, these spiders—when moving full speed—can complete three full rotations. Their spin is the fastest leg-driven turning maneuver of any terrestrial animal, and also one of the fastest turns on the planet—on par with quick airborne spinners like hummingbirds and fruit flies."

Comment: Amazing muscle coordinatiion based on a tiny spider brain which senses air current changes in their nocturnal environment. Be sure to go to the website to see the action video.