Shenrich91 via Wikimedia Commons // CC BY-SA 3.0
Shenrich91 via Wikimedia Commons // CC BY-SA 3.0

Black Widows’ Hourglass Markings Deter Potential Predators

Shenrich91 via Wikimedia Commons // CC BY-SA 3.0
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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3 Simple Ways to Stay Tick-Free This Summer
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As the weather gets warmer, you no doubt want to don your favorite shorts and get out in the sunshine. Unfortunately, shorts season coincides with tick season, and we're in the midst of what one expert calls a "tick explosion."

Tick expert Thomas Mather of the University of Rhode Island told Boston 25 News that warm weather is going to lead to a particularly bad summer for ticks. The blood-sucking bugs aren't just annoying—they spread Lyme disease and several other serious illnesses, including a pathogen that can cause a sudden allergy to meat.

There are several precautions you should take to stay safe from ticks and the risks they carry during the high season, which usually lasts from April to September, though some ticks can stay active year-round as long as it's above freezing. While ticks usually live in grassy or wooded areas, you should be careful even if you live in the city, because pathogen-spreading ticks can still be hiding in urban parks.

Tick prevention begins when you get dressed. Wear long sleeves and pants, and if you're in a tick-prone area, tuck your pants into your socks to better protect your legs. Opt for light colored clothing, because it's easier to see bugs against a light color versus a dark one.

You'll want to invest in insect repellent, too, for both you and your pets. The CDC recommends treating your clothing (and tents, and any outdoor gear) with permethrin, an insecticide that you can apply to fabric that will last through several washes. Permethrin not only repels ticks, but kills them if they do manage to get onto your clothes, and you can buy socks and other clothing that come pre-treated with it. Insect repellents with DEET are also effective against ticks.

Since ticks are most likely to make their way onto your feet and ankles, make sure to treat your shoes and socks. And since your dog is more likely to get a tick than you are, make sure to get Fido a tick collar or some other kind of tick medication.

Most of all, you just need to stay vigilant. When you come inside from the outdoors, check your body for any ticks that may have latched on. Ticks can be as small as a poppyseed, so make sure to look closely, or ask someone else to check hard-to-see places like your back. And since they like moist areas, don’t forget to give your armpits and groin a careful look. If you do catch a tick, remove it as soon as you can with a pair of tweezers.

Best of luck out there.

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Watch a "Trained" Spider Named Kim Leap Six Times Its Body Length
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Jumping spiders are cold-blooded assassins, masters of disguise, and just maybe a little quicker on the uptake than we're really OK with. For a study published in the journal Scientific Reports, a team of researchers from the University of Manchester "trained" one special jumping spider named Kim to leap in their experiment, all with the goal of demystifying the mechanics behind jumping spiders' abilities.

Kim was one of four regal jumping spiders (Phiddipus regius) the researchers brought into the lab for a close examination of how their bodies move as they leap and land. A jumping spider can clear up to six times its body length, which ranges from 0.04 to 0.98 inches—about the equivalent of a three-story building, relative to the spider's body size. For comparison, the farthest a human can jump is roughly 1.5 body lengths.

The researchers created an experiment chamber with platforms at varying distances from one another, then tried to coax the spiders into it. Only Kim would even enter. The researchers moved Kim between the take-off and landing platforms until she "became familiar with the challenge," they write. No tasty bait or stimulation (like blowing air) was used to motivate her. Still, her eventual familiarity with the task potentially implies some sort of learning. So even though she wasn't following orders, she figured out how to navigate the experiment's challenges—an impressive achievement for a spider about the size of an aspirin.

Using ultra-high-speed and high-resolution cameras, the researchers then filmed Kim's jumps to study how the arachnid moved her body when navigating a short jump equal to two body lengths; a longer jump equal to six lengths; and jumps between platforms placed at different heights. They found that Kim cleared shorter distances quickly and at low angles, thus sharpening her accuracy and boosting her chances of catching any prey that might be waiting at her destination. For longer jumps, she was more conservative with her energy, but her accuracy suffered.

Jumping spiders are excellent hunters, thanks in part to their precision ambushing skills. They also boast super-powered senses that help them locate their next meal before making their attack. Fine hairs on their legs allow them to "hear" subtle vibrations, and their eight eyes are sharp enough to track laser pointer lights.

This family of spiders also uses a hydraulic pressure system to move their legs. It helps jumping spiders extend their limbs, and some researchers have theorized that it also allows them to jump such great distances. According to the new study, that's not the case: "Our results suggest that whilst Kim can move her legs hydraulically, she does not need the additional power from hydraulics to achieve her extraordinary jumping performance," study co-author Bill Crowther said in a press statement. That means the jumps in the video below are made possible by Kim's muscle power alone.

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