This high speed maneuver is a nightmare if you are a fly.
There is a kind of spider that can slowly tension and then release its net, catapulting the net forward and capturing unsuspecting prey in its threads.
Dreieckweberspinnen use their own net like humans a slingshot or a crossbow. University of Akron scientists say this is a process called "power amplification". This week they published their research findings in Proceedings of the National Academy of Sciences is stretchable, which allows the spider to strengthen their own power by what the scientists call "elastic recoil". Co-author of the study, Daniel Maksuta, a physicist at the University of Akron, tells NPR that the maneuver "causes much greater forces and thus much greater accelerations".
Scientists say the spin-like motions show that spiders can use a tool, their own net, just as people are used to.
Think of spiders that load energy into a spider web and then use it to catch prey, "said Sheila Patek, biologist and animal movement mechanics expert at Duke University She said, "I can not imagine another example where an animal, as you know, takes something from outside that they built and then loaded."
That's how it works the movement: A triangular weaving spider creates a triangular web, with a single thread bridging the main body of the triangle and a wall, and then, as it grabs that single thread, it "wanders" backwards, tensing the web so that it has elastic energy throughout Sarah Han, a biologist at the University of Akron and lead author of the study.
The spider wraps the single strand between her legs closer and closer together than she would pull back a rubber band. Han says she saw spiders for hours waiting for prey to fall into the net.
"When it senses that prey hits the net, it releases its legs from the back line," Han says. "And that causes the spider and the net to leap forward with this release of energy as if you had released that rubber band … This causes vibrations in the net that involve the loot."
The spider can repeat this several times by tightening and releasing the net, causing the prey to become more and more entangled and stuck.
The net and spider leap forward at incredible speed – Han says this equates to about 400 spider body lengths per second.
To investigate how the spiders performed this maneuver, Han said the scientists had collected triangular spiders near the University of Ohio and had nets built in the lab. They then trapped the nets in terrariums and released flies into them. Eventually the fly would fall into the web of the spider while the scientists watched.
"We recorded it all with high-speed video cameras," says Han, and then they used "motion tracking and software to get the positional data, and from that we can get things like speed and acceleration."
Han says this is not the first time anyone has noticed the spider's impressive maneuver, but "no one actually quantified it" until they studied it.
It is worth noting that there are many different types of spiders that use their nets in different ways. Example: Spherical web spiders form circular, spiral-shaped nets, which you probably come to mind when you imagine what a spider web looks like. This type of spider does not fire its net for prey – the net stays static.
In addition, the scientists say that when they think about "performance enhancement," biologists usually describe how animals store and release energy in their own body. There are many examples of this, such as the jumping of fleas and frogs and the sharp beating of a Mantis shrimp.
However, the scientists said that the triangular spider had essentially no need to develop new methods to store and release energy in its body like the other animals – because it adopted its own tool, a net, as a weapon.