Spider Uses Web As Slingshot To Ensnare Prey, Scientists Find

A triangle-weaver spider holds its web in tension.

S.I. Han


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S.I. Han

This high-velocity maneuver is a nightmare if you’re a fly.

There’s a type of spider that can slowly stretch its web taut and then release it, causing the web to catapult forward and ensnare unsuspecting prey in its strands.

Triangle-weaver spiders use their own web the way humans might use a slingshot or a crossbow. Scientists from the University of Akron say this is a process called “power amplification,” and they published their research in Proceedings of the National Academy of Sciences this week.

The web is stretchy, which allows the spider to amplify its own power by using what the scientists call “elastic recoil.” Study co-author Daniel Maksuta, a physicist at the University of Akron, tells NPR that the maneuver “causes much larger forces and therefore much larger acceleration.”

Scientists say the slingshot-like move shows spiders can use a tool, their own web, in a way that only humans were known to do.

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Credit: PNAS

“I think it’s just an amazing image to think of — spiders loading up energy in a spiderweb and then deploying it to catch prey,” says Sheila Patek, a Duke University biologist and expert in the mechanics of animal movement, who was not involved in the study. Besides humans, she says, “I can’t think of another example where an animal, you know, takes something externally that they’ve built and then loaded it up” in the same way.

Here’s how the move works: A triangle-weaver spider makes a triangle-shape web, with a single thread bridging the main body of the triangle and a wall. Then, while gripping that single thread, “it walks backward and it tightens the web so it’s storing this elastic energy within the whole triangle shape of the web,” says Sarah Han, a biologist at the University of Akron and the study’s lead author.

The spider coils the single strand between its legs tighter and tighter, as if it is pulling back a rubber band. Han says she has seen spiders hold that coiled strand for hours, waiting for prey to fall into the web.

A triangle-weaver spider uses its back legs to hold a coiled anchor line, which it built up while stretching and tensing the web.

S.I. Han


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S.I. Han

“When it senses prey hitting the web it releases its legs from the back line,” says Han. “And this causes the spider and the web to spring forward with that release of energy, as if you had released that rubber band. … This causes oscillations in the web that start to entangle the prey.”

She says the spider may repeat this multiple times, tightening and then releasing the web so the prey gets more and more tangled and trapped.

The web and spider spring forward together with incredible velocity — Han says it’s the equivalent of traveling some 400 of the spider’s body lengths per second.

To study how the spiders carried out this maneuver, Han says the scientists collected triangle-weaver spiders near the university in Ohio and had them build webs in the lab. They then enclosed the webs in terrariums and would release flies into them. Eventually, the fly would fall into the spider’s web as the scientists looked on.

“We were recording all of this with high-speed video cameras,” Han says, and then they would use “motion tracking and software to get the position data, and from that we can get things like velocity and acceleration.”

Han says this isn’t the first time someone has noticed the spider’s impressive maneuver, but “no one had actually quantified it” until their study.

It’s worth noting that there are many different kinds of spiders, and they use their webs in different ways. For example, orb-weaver spiders make the kind of circular, spiral webs that probably come to mind when you think of what a spiderweb looks like. That kind of spider doesn’t fire its web at prey — the web stays static.

Additionally, the scientists say that typically when biologists think about “power amplification,” they’re describing how animals store and release energy within their own bodies. There are many examples of this, such as the jumping of fleas and frogs, and the sharp strike of a mantis shrimp.

But the scientists say the triangle-weaver spider largely didn’t need to evolve ways to store and release energy within its body like those other animals — because it adapted its own tool, a web, as a weapon.

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Ex-USC Coach Behind Fake Athletic Profiles In College Admissions Scam, Pleads Guilty

Former University of Southern California soccer coach Laura Janke exiting a Boston federal court Tuesday, where she pleaded guilty to charges in a nationwide college admissions bribery scandal.

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A former University of Southern California soccer coach who created phony athletic profiles for the sons and daughters of wealthy parents pleaded guilty to a racketeering conspiracy charge on Tuesday.

Laura Janke had previously denied taking bribes for writing the fake sports biographies, but she is now the fourth corrupt coach to plead guilty in the ongoing college admissions scandal conceived by mastermind William “Rick” Singer.

In a federal court appearance in Boston, the 36-year-old calmly admitted she accepted at least $130,000 in illegal payouts. According to prosecutors, the money was funneled from a sham charity run by Singer to a soccer camp run by Janke and Ali Khosroshahin, the head coach of USC women’s soccer.

Under a plea agreement Janke signed last month, she has been cooperating with prosecutors who say she could testify against others charged in the case, including actress Lori Loughlin and her husband, fashion designer Mossimo Giannulli.

The former assistant women’s soccer coach was behind a number of bogus sports profiles, including the one that helped get Laughlin and Giannulli’s daughter, Olivia Jade Giannulli, accepted into the prestigious school as a crew recruit despite never having been rowers on a competitive crew team. Janke said she later did the same for Loughlin’s other daughter, Isabella Rose.

Loughlin and her husband deny they paid $500,000 to get their daughters recruited to the USC crew team. They have maintained their innocence and have decided to fight the charges.

Janke’s influence extended beyond USC’s red brick campus, according to prosecutors. She concocted profiles for students who were subsequently accepted into the University of California, Los Angeles; Stanford University; and Georgetown University.

Dozens of other prominent parents as well as test proctors and college consultants have been implicated in the scandal.

On Monday, Desperate Housewives star Felicity Huffman tearfully pleaded guilty to conspiracy to commit mail fraud and honest services mail fraud.

Huffman admitted to paying someone $15,000 to boost her daughter’s SAT scores by combing through and correcting wrong answers on the test.

“[Huffman] cried as she explained to the judge that her daughter knew nothing about the scam to inflate her test scores, and that her daughter’s accommodation for extra time on tests was legitimate,” NPR’s Tovia Smith reported.

Huffman now faces four months in prison. The person who made the corrections has also pleaded guilty. But the exam proctor who allegedly allowed the cheating, has pleaded not guilty.

Janke faces 27 to 33 months in prison. In exchange for her cooperation, prosecutors recommend a sentence at the low end of that range.

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Trump Jr. Strikes Deal With Senate Intelligence Committee For Additional Testimony

Donald Trump Jr., the president’s eldest son, has reached a deal to testify before the Senate Intelligence Committee next month.

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Donald Trump Jr. has reached a compromise with the Senate Intelligence Committee to testify before the panel, according to a source familiar with the negotiations. The deal comes less than a week after the committee’s initial subpoena inflamed tensions between the GOP-led panel and the White House.

The mid-June interview will be limited in time — no more than four hours — although no topics are off limits, the source said.

The primary agenda is expected to focus on knowledge Trump Jr. may have about the proposed Trump Tower Moscow project as well as his involvement in a June 2016 meeting at Trump Tower in New York City with a Russian delegation after an offer of “dirt” on Hillary Clinton.

A Senate Intelligence Committee spokesperson declined to comment.

Trump Jr. first testified before the committee about such questions in December 2017. Negotiations over another appearance dragged on and eventually stalled, leading to the subpoena compelling the president’s son to testify or risk being held in contempt.

The debate over another round of testimony comes at a time when tensions are inflamed between President Trump and Capitol Hill over executive privilege — though most of that has centered on information the Democratic-controlled House is trying to obtain.

In the Republican-controlled Senate, Majority Leader Mitch McConnell, R-Ky., has declared “case closed” on special counsel Robert Mueller’s investigation. The White House saw the findings as vindication. The report did not find conspiracy between the Trump campaign and Russia on election interference. And while the special counsel did not conclude one way or another whether the president obstructed justice, Attorney General William Barr has cleared the president on that question.

But this latest request for testimony from Trump Jr. comes from one of the Senate’s more bipartisan committees, and its chairman, North Carolina Republican Richard Burr, has seemed unmoved by any criticisms from within his party.

Trump himself weighed in earlier Tuesday as he departed the White House for Louisiana, saying that it was “very unfair” how his eldest child was being treated.

“It’s really a tough situation because my son spent I guess over 20 hours testifying about something that Mueller said was 100 percent OK,” Trump told reporter. “And now they want him to testify again. I don’t know why. I have no idea why. But it seems very unfair to me.”

Later on Tuesday, McConnell said, however, that it was the Senate Intelligence Committee chairman’s prerogative on how to run his panel.

“None of us tell Chairman Burr how to run his committee,” McConnell said. “I asked him to undertake this investigation on Russian collusion a couple of years ago. He’s indicated publicly that he believes they will find no collusion and we are hoping to get a report on that subject very soon.”

But the Senate GOP leader declined to answer a question about whether he agreed with Trump’s comments about the subpoena and repeated he expected to get the intelligence report soon.

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