Flies and mosquitoes take care of fit, here comes the tip of the clutch

Running an invisible spider web in the woods can be scary enough, but what if you have to worry about a spider web – and the spider – catapulting near you? That’s what happens to insects in Peru’s Amazon rainforests, where a small pinhead launches a web – and himself – to catch unsuspecting flies and mosquitoes.

Researchers from the Georgia Institute of Technology have produced what may be the first cinematic study of how this powerful arachnid stores enough energy to produce acceleration of 1,300 meters / second²—100 times the acceleration of a cheetah. That acceleration produces speeds of 4 meters per second and subjects the spin to forces of about 130 Gs, more than 10 times what fighter pilots can withstand without blacking out.

The Peruvian spider and its nephews stand out among arachnids for their ability to create external tools – in this case, their webs – and use them as jumps to create ultrafast motion. Their ability to wait hours for a spring ready for launch while waiting for an impending mosquito suggests another great tool: a ratchet mechanism to release the spring.

“Unlike frogs, crickets, or locusts, the splash bar does not rely on its muscles to jump very fast,” said Saad Bhamla, an assistant professor at Georgia Tech’s School of Chemical and Biomolecular Engineering who studies ultra-solid organisms. “When it weaves a new web every night, the spider creates a complex, three-dimensional spring. If you compare this natural silk spring to carbon nanotubes or other man-made materials in terms of power density or energy density, it’s orders of magnitude more powerful. . “

The study, supported by the National Science Foundation and National Geographic Society Foundation, was published Aug. 17 in the journal Current biology. Understanding how websites’ energy storage could potentially provide new sources of power for small robots and other devices, and lead to new applications for the robust material, the researchers say.

Slingshot spiders, known by the scientific genus name Theridiosomatid, build three-dimensional conical webs with a tension line attached to the center. The Peruvian member of that spider family, which is about 1 millimeter in length, pulls the tension line with his front legs to stretch the structure while holding on to the web with his hind legs. When it reaches a meal within reach, the spider launches the web and itself towards a fly or mosquito.

If the launch is successful, the spider quickly wraps its flour in silk. If the spin is missing, it simply pulls the tension line to reset the web for the next chance.

“We think this approach is likely to give the spider the benefit of speed and surprise, and perhaps even astonish the effect of the prey,” notes Symone Alexander, a postdoctoral researcher in Bhamla’s lab. “The spiders are spicy, and they go after flying insects that are bigger than they are. To catch one, you have to be much, much faster than they are.”

Slingshot spiders were described in a 1932 publication, and more recently by Jonathan Coddington, now a senior research entomologist at the Smithsonian Institution. Bhamla has an interest in fast-moving but small organisms, so he and Alexander arrange a trip to study catapulting beings with ultra-fixed cameras to measure and record the movement.

“We wanted to understand these ultra-fast movements because they could force our perspective to change thinking about cheetahs and falcons as the only fast animals,” Bhamla said. “There are a lot of very small invertebrates that can achieve rapid motion through unusual structures. We really wanted to understand how these spiders achieve that tremendous acceleration.”

The researchers traveled six hours by boat from Puerto Maldonado to the Tambopata Research Center. There is no electricity in the area, so nights are very dark. “We looked up and saw a small red dot,” Bhamla recalled. “We were so far away from the nearest light that the dot turned out to be the planet Mars. We could see the Milky Way so clearly, too.”

The intense darkness raises the question of how the spider senses its prey and determines where to direct itself. Bhamla believes it should be an acoustic sensor technique, a theory supported by the way researchers tricked the spider into launching its web: They just snapped their fingers.

Beyond sensing in the dark, the researchers also asked themselves how the spider triggers the release of the web. “When an insect comes within reach, the spider releases a small bundle of silk that it has created by crawling along the tension line,” Alexander said. “Releasing the bundle controls how far the web flies. Both the spider and the web move backwards.”

Another mystery is how the spider patiently holds the web while waiting for food to fly through. Alexander and Bhamla estimated that stretching the web requires at least 200 dunes, a tremendous amount of energy for a small spin to generate. Holding that for hours could waste a lot of energy.

“Generating 200 dunes would produce tremendous forces on the small legs of the spider,” Bhamla said. “If the reward at the end of three hours is a mosquito, is that worth the effort? We think the spider should use some trick to secure his muscles like a latch so she doesn’t have to consume energy when she does. waiting hours. “

Besides curiosity, why are you traveling to Peru to study the creature? “The spike spider provides an example of active hunting instead of passive. Waiting for an insect to collide with the web strategy, revealing a further new feature of spin silk,” said Bhamla. “For this, we had not thought about using silk as a really powerful spring.”

Another unintended advantage is changing attitude towards spiders. Before the study, Alexander admits she had a fear of spiders. That was surrounded by banners in the Peruvian jungle – and seeing the amazing things they do – changed that.

“In the rainforest at night, when you shine your flashlight, you quickly see that you are completely surrounded by spiders,” she said. “In my house, we do not kill spiders anymore. If they are accidentally scared and in the wrong place, we will safely move them to another location.”

Alexander and Bhamla had hoped to return to Peru this summer, but those plans were cut short by the coronavirus. They like to continue learning the spider.

“Nature does many things better than humans can do, and nature has done them much longer,” she said. “Being in the field gives you a different perspective, not only on what nature does, but also why that is necessary.”