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Shenrich91 via Wikimedia Commons // CC BY-SA 3.0

Black Widows’ Hourglass Markings Deter Potential Predators

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Shenrich91 via Wikimedia Commons // CC BY-SA 3.0

Everyone knows to watch their step around a black widow—including predatory birds. A new study shows that birds know to avoid the spiders based on their bright red markings. Meanwhile, the spiders' prey has a much more difficult time making out the markings, leaving them unaware of the lurking danger. The findings of the study were published last week in the journal Behavioral Ecology.

The species collectively known as black widows hold a special place in the human imagination. The pop mythology surrounding the female black widow’s potent venom and characteristic red hourglass markings have inspired songwriters, comic book creators, and even video game designers—a fact that the authors of the current study exploited. 

“Video game developers love to put black widows in their games because they’re scary,” lead author Nicholas Brandley said in a press release. Brandley and his colleagues bought a digitally rendered black widow (in this case, Latrodectus mactans) from a video game developer. They adapted the code for a 3D printer, and made black widow models in the lab. Four of the eight fake spiders were painted all black. The other four got the full killer-spider treatment in "Heavy Body Mars Black" and "Berry Red"—commercially available colors that closely match the coloration of live black widows. 

Actual spider belly. Image Credit: Nicholas Brandley

The scientists started by testing spider-eating birds. They set up seven bird feeders around Durham County, North Carolina, and replenished them daily with seeds so local birds would get used to visiting. Then, on test day, they took all the seeds away and replaced them with a single fake spider, laid belly up. 

They watched as the birds (Carolina chickadees, northern cardinals, tufted titmice, white breasted nuthatches, and two kinds of woodpeckers) approached the feeders. They found that the birds were 2.9 times more likely to attack the plain black spiders than the faux black widows. Smaller birds were especially likely to take off at the sight of the red hourglass. “The birds would see a spider model with red markings and get startled and jump back, like ‘Oh no man, get me out of here,’” Brandley said in the press release. 

Clearly, the birds could see the spiders’ markings and understood what they meant.

Next, the researchers measured the wavelengths of light given off by the markings of two black widow species. Bird eyes, human eyes, and insects all pick up different wavelengths, which affects how we all perceive color. They found that the black widows’ red markings are half as visible for insects as for birds. 

The scientists then wondered if viewing angle had anything to do with it, since black widows like to hang belly-up beneath their webs. This position would display the red markings to spider-eating birds flying overhead while conveniently concealing them from insects below. 

To find out, they set up 20-inch-tall “widow towers” in the lab, brought in two real black widow species (L. variolus and L. mactans), and let them set up house. Time and time again, L. variolus spiders, which also had red marks on their backs, built their webs higher in the tower than spiders from the other species, which did not. This suggests that the L. variolus spiders were raising their vivid markings even farther from insect view, making them harder to see. 

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Lucy Stockton/National Trust Images
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This Just In
The Tiny, Pretty Diamond Spider Isn't Extinct After All
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Lucy Stockton/National Trust Images

An elusive spider that was believed to be extinct in Britain has been spotted for the first time in nearly 50 years, according to The Telegraph.

Pretty little Thanatus formicinus—more commonly known as the diamond spider—is just a third of an inch long and gets its name from the thin black diamond on its hairy gray abdomen. The spider typically lives in damp areas with moss and flowering plants, like heather and purple moor grass. But since the arachnid was last spotted in England’s Ashdown Forest in 1969, conservationists assumed that it had fallen victim to habitat loss.

Turns out, the spider wasn’t extinct—it was just laying low for a few decades. While conducting an ecological survey of Clumber Park—an expanse of heath, woods, and parkland in Nottinghamshire—two volunteers with England’s National Trust conservation organization recently spotted the long-lost arachnid.

“The spider ran away from me twice, but with persistence and some luck, I caught it,” said Lucy Stockton, the National Trust volunteer who sighted the arachnid along with companion Trevor Harris.

The duo’s discovery in Clumber Park marks just the fourth time the spider had ever been recorded in the UK, and the only time it's been seen in the north of the country. “We are absolutely delighted that this pretty, little spider has been re-found, we had almost given up hope,” commented Mark Shardlow, the chief executive of Buglife, an English conservation group. “It is a testament to the crucial importance of charities like the National Trust saving and managing heathland habitats.”

[h/t The Telegraph]

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20th Century Fox Home Entertainment
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entertainment
The Peppa Pig Episode Kids in Australia Can't See
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20th Century Fox Home Entertainment

Kids in Australia have reason to be wary of eight-legged creatures. The continent is home to some pretty dangerous spiders, including deadly funnel-web spiders, which have strong enough fangs to bite through a toenail. Australia's spiders have claimed a new victim, though: a few episodes of the animated British show Peppa Pig.

As Slate reports, an episode of the show has been pulled from the broadcast lineup in Australia for urging kids not to be afraid of spiders. The episode, "Mister Skinnylegs," first aired in 2004, and had already been banned from public broadcasting in 2012, but it recently re-ran on Nick Jr. through the Australian cable service Foxtel. Another episode featuring the same spider character, "Spider Web," is also banned in the country.

In "Mister Skinny Legs," Peppa Pig's brother George finds a spider in the sink and becomes its friend. Peppa is scared at first, but her father tells her, "There's no need to be afraid. Spiders are very, very small, and they can't hurt you."

Arguing that Down Under, spiders can, in fact, hurt you, parents complained that the episode was inappropriate for impressionable Australian viewers. After the outcry following the August 25 re-run, Nick Jr. has agreed to pull the episode from rotation in Australia.

While Australia does have some scary spiders, the risk may be a bit overblown. In a recent study, researchers found zero deaths from spider bites in the country between 2000 and 2013. (There was one fatality in 2016, but it was the first in 37 years.) Almost 12,000 people did end up in the hospital with spider bites during those years, though. On the other hand, the same study found that more Australians were killed by horses during that time period than all of the country's venomous creatures combined. Still, it's perhaps best to avoid telling kids to make friends with black widows. Watch the episode below at your own risk.

[h/t Slate]

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