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3 Sneaky Chemical Tricks Used by Animals

1. These are not the frogs you’re looking for

On the savannahs of West Africa, stink ants (Paltothyreus tarsatus) are well known for their aggressive foraging raids, in which huge numbers of ants hunt together for larger insects and even vertebrate animals as large as frogs and rodents. The ants are just as dangerous at home, and will defend their colonies and kill intruders with powerful bites and venomous stings. 

They don’t seem like they’d make good roommates, but they’re exactly what the West African Rubber Frog (Phrynomantis microps) is looking for. The ants' nests are nice and humid and keep the frog’s skin moist during the long dry season, and the ferocity with which the ants guard their home means the frog doesn’t have to worry about other predators. 

If any other frog tried to move in to a stink ant colony, it would be attacked and stung immediately, but the ants seem to ignore the Rubber Frog completely. This is because the frog uses what’s sort of a chemical Jedi mind trick. Most social insects like ants use chemical cues to communicate and recognize each other. To get along with its potentially less-than-gracious hosts, the frog coats its skin with compounds that tell the ants, in their chemical language, to leave it alone. 

The frog’s skin secretions are an allomone, an animal-produced chemical signal that benefits the sender by altering the behavior of the receiver. Some allomones work as repellants that keep predators away. Others attract unwitting prey. The one used by the Rubber Frog seems to work as what scientists call an appeasement substance. It curbs the ants’ aggression and delays their attack by saying, Nope, don’t mind me—I’m not making trouble

The allomone even works when it's not the frog wearing it. When researchers covered mealworms and termites with skin secretions from a Rubber Frog and offered them to ants, the ants ignored the treats for several minutes until the secretions dried and the effect wore off. 

2. Looks like a silverfish, smells like an ant

Thinkstock

The silverfish Malayatelura ponerphila also lives among ants in their nests, but takes a slightly different approach to blending in. Instead of appeasing its hosts, M. Ponerophila disguises itself as one of them. 

Because the chemical signals the ants use to communicate are so widely distributed through their colonies, say biologists Freddie-Jean Richard and Jim Hunt, each colony takes on a specific odor that help its members tell nestmates and intruders apart. M. Ponerophila borrows this chemical uniform by sneaking into a colony and rubbing its body against defenseless larvae, pupae, and callows (immature ants) to pick up the compounds that form the colony’s signature odor. 

As long as a silverfish keeps this scent on itself, it gets access to shelter in the nest and the ants’ food stores, without having to contribute anything to the colony. Like stink ants, though, the army ants that M. Ponerophila lives with in Malaysia are very aggressive, and silverfish that are separated from their scent supply and recognized as intruders are frequently attacked and killed. 

3. Sheep in wolf’s clothing

Chemical trickery isn’t just for sneaking into ant colonies. Two different squirrel species are known to chew on rattlesnake sheds and then lick themselves, anointing their fur with odor compounds from the old skin. As with the silverfish, this gives the squirrel a chemical disguise that helps it hide its own squirrel-y scent from snakes.

The rattler perfume also seems to help the squirrels by changing their behavior. Researchers noticed that squirrels that had recently applied snake scent to their fur groomed themselves more and rested less. The squirrels, the researchers thought, had fooled themselves a little with their disguise, too, and were going through a stress response to the scent of a predator—which helped make them more alert in case an actual snake showed up.

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iStock // Ekaterina Minaeva
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Man Buys Two Metric Tons of LEGO Bricks; Sorts Them Via Machine Learning
May 21, 2017
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iStock // Ekaterina Minaeva

Jacques Mattheij made a small, but awesome, mistake. He went on eBay one evening and bid on a bunch of bulk LEGO brick auctions, then went to sleep. Upon waking, he discovered that he was the high bidder on many, and was now the proud owner of two tons of LEGO bricks. (This is about 4400 pounds.) He wrote, "[L]esson 1: if you win almost all bids you are bidding too high."

Mattheij had noticed that bulk, unsorted bricks sell for something like €10/kilogram, whereas sets are roughly €40/kg and rare parts go for up to €100/kg. Much of the value of the bricks is in their sorting. If he could reduce the entropy of these bins of unsorted bricks, he could make a tidy profit. While many people do this work by hand, the problem is enormous—just the kind of challenge for a computer. Mattheij writes:

There are 38000+ shapes and there are 100+ possible shades of color (you can roughly tell how old someone is by asking them what lego colors they remember from their youth).

In the following months, Mattheij built a proof-of-concept sorting system using, of course, LEGO. He broke the problem down into a series of sub-problems (including "feeding LEGO reliably from a hopper is surprisingly hard," one of those facts of nature that will stymie even the best system design). After tinkering with the prototype at length, he expanded the system to a surprisingly complex system of conveyer belts (powered by a home treadmill), various pieces of cabinetry, and "copious quantities of crazy glue."

Here's a video showing the current system running at low speed:

The key part of the system was running the bricks past a camera paired with a computer running a neural net-based image classifier. That allows the computer (when sufficiently trained on brick images) to recognize bricks and thus categorize them by color, shape, or other parameters. Remember that as bricks pass by, they can be in any orientation, can be dirty, can even be stuck to other pieces. So having a flexible software system is key to recognizing—in a fraction of a second—what a given brick is, in order to sort it out. When a match is found, a jet of compressed air pops the piece off the conveyer belt and into a waiting bin.

After much experimentation, Mattheij rewrote the software (several times in fact) to accomplish a variety of basic tasks. At its core, the system takes images from a webcam and feeds them to a neural network to do the classification. Of course, the neural net needs to be "trained" by showing it lots of images, and telling it what those images represent. Mattheij's breakthrough was allowing the machine to effectively train itself, with guidance: Running pieces through allows the system to take its own photos, make a guess, and build on that guess. As long as Mattheij corrects the incorrect guesses, he ends up with a decent (and self-reinforcing) corpus of training data. As the machine continues running, it can rack up more training, allowing it to recognize a broad variety of pieces on the fly.

Here's another video, focusing on how the pieces move on conveyer belts (running at slow speed so puny humans can follow). You can also see the air jets in action:

In an email interview, Mattheij told Mental Floss that the system currently sorts LEGO bricks into more than 50 categories. It can also be run in a color-sorting mode to bin the parts across 12 color groups. (Thus at present you'd likely do a two-pass sort on the bricks: once for shape, then a separate pass for color.) He continues to refine the system, with a focus on making its recognition abilities faster. At some point down the line, he plans to make the software portion open source. You're on your own as far as building conveyer belts, bins, and so forth.

Check out Mattheij's writeup in two parts for more information. It starts with an overview of the story, followed up with a deep dive on the software. He's also tweeting about the project (among other things). And if you look around a bit, you'll find bulk LEGO brick auctions online—it's definitely a thing!

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Library of Congress
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10 Facts About the Tomb of the Unknown Soldier
May 29, 2017
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Library of Congress

On Veterans Day, 1921, President Warren G. Harding presided over an interment ceremony at Arlington National Cemetery for an unknown soldier who died during World War I. Since then, three more soldiers have been added to the Tomb of the Unknowns (also known as the Tomb of the Unknown Soldier) memorial—and one has been disinterred. Below, a few things you might not know about the historic site and the rituals that surround it.

1. THERE WERE FOUR UNKNOWN SOLDIER CANDIDATES FOR THE WWI CRYPT. 

Wikimedia Commons // Public Domain

To ensure a truly random selection, four unknown soldiers were exhumed from four different WWI American cemeteries in France. U.S. Army Sgt. Edward F. Younger, who was wounded in combat and received the Distinguished Service Medal, was chosen to select a soldier for burial at the Tomb of the Unknowns in Arlington. After the four identical caskets were lined up for his inspection, Younger chose the third casket from the left by placing a spray of white roses on it. The chosen soldier was transported to the U.S. on the USS Olympia, while the other three were reburied at Meuse Argonne American Cemetery in France.

2. SIMILARLY, TWO UNKNOWN SOLDIERS WERE SELECTED AS POTENTIAL REPRESENTATIVES OF WWII.

One had served in the European Theater and the other served in the Pacific Theater. The Navy’s only active-duty Medal of Honor recipient, Hospitalman 1st Class William R. Charette, chose one of the identical caskets to go on to Arlington. The other was given a burial at sea.

3. THERE WERE FOUR POTENTIAL KOREAN WAR REPRESENTATIVES.

WikimediaCommons // Public Domain

The soldiers were disinterred from the National Cemetery of the Pacific in Hawaii. This time, Army Master Sgt. Ned Lyle was the one to choose the casket. Along with the unknown soldier from WWII, the unknown Korean War soldier lay in the Capitol Rotunda from May 28 to May 30, 1958.

4. THE VIETNAM WAR UNKNOWN WAS SELECTED ON MAY 17, 1984.

Medal of Honor recipient U.S. Marine Corps Sgt. Maj. Allan Jay Kellogg, Jr., selected the Vietnam War representative during a ceremony at Pearl Harbor.

5. BUT THE VIETNAM VETERAN WASN'T UNKNOWN FOR LONG.

Wikipedia // Public Domain

Thanks to advances in mitochondrial DNA testing, scientists were eventually able to identify the remains of the Vietnam War soldier. On May 14, 1998, the remains were exhumed and tested, revealing the “unknown” soldier to be Air Force 1st Lt. Michael Joseph Blassie (pictured). Blassie was shot down near An Loc, Vietnam, in 1972. After his identification, Blassie’s family had him moved to Jefferson Barracks National Cemetery in St. Louis. Instead of adding another unknown soldier to the Vietnam War crypt, the crypt cover has been replaced with one bearing the inscription, “Honoring and Keeping Faith with America’s Missing Servicemen, 1958-1975.”

6. THE MARBLE SCULPTORS ARE RESPONSIBLE FOR MANY OTHER U.S. MONUMENTS. 

The Tomb was designed by architect Lorimer Rich and sculptor Thomas Hudson Jones, but the actual carving was done by the Piccirilli Brothers. Even if you don’t know them, you know their work: The brothers carved the 19-foot statue of Abraham Lincoln for the Lincoln Memorial, the lions outside of the New York Public Library, the Maine Monument in Central Park, the DuPont Circle Fountain in D.C., and much more.

7. THE TOMB HAS BEEN GUARDED 24/7 SINCE 1937. 

Tomb Guards come from the 3rd U.S. Infantry Regiment "The Old Guard". Serving the U.S. since 1784, the Old Guard is the oldest active infantry unit in the military. They keep watch over the memorial every minute of every day, including when the cemetery is closed and in inclement weather.

8. BECOMING A TOMB GUARD IS INCREDIBLY DIFFICULT.

Members of the Old Guard must apply for the position. If chosen, the applicant goes through an intense training period, in which they must pass tests on weapons, ceremonial steps, cadence, military bearing, uniform preparation, and orders. Although military members are known for their neat uniforms, it’s said that the Tomb Guards have the highest standards of them all. A knowledge test quizzes applicants on their memorization—including punctuation—of 35 pages on the history of the Tomb. Once they’re selected, Guards “walk the mat” in front of the Tomb for anywhere from 30 minutes to two hours, depending on the time of year and time of day. They work in 24-hour shifts, however, and when they aren’t walking the mat, they’re in the living quarters beneath it. This gives the sentinels time to complete training and prepare their uniforms, which can take up to eight hours.

9. THE HONOR IS ALSO INCREDIBLY RARE.

The Tomb Guard badge is the least awarded badge in the Army, and the second least awarded badge in the overall military. (The first is the astronaut badge.) Tomb Guards are held to the highest standards of behavior, and can have their badge taken away for any action on or off duty that could bring disrespect to the Tomb. And that’s for the entire lifetime of the Tomb Guard, even well after his or her guarding duty is over. For the record, it seems that Tomb Guards are rarely female—only three women have held the post.

10. THE STEPS THE GUARDS PERFORM HAVE SPECIFIC MEANING.

Everything the guards do is a series of 21, which alludes to the 21-gun salute. According to TombGuard.org:

The Sentinel does not execute an about face, rather they stop on the 21st step, then turn and face the Tomb for 21 seconds. They then turn to face back down the mat, change the weapon to the outside shoulder, mentally count off 21 seconds, then step off for another 21 step walk down the mat. They face the Tomb at each end of the 21 step walk for 21 seconds. The Sentinel then repeats this over and over until the Guard Change ceremony begins.

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