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The Hunting Strategies of Carnivorous Plants

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Not the blood-thirsty Audrey II from Little Shop of Horrors "“ we're talking about the very real plants that feast on insects and invertebrates. Carnivorous plants are usually found in environments with low-nutrient soil, like bogs and swamps, where they thrive on the sunshine and warm temperatures. Contrary to popular belief, carnivorous plants don't derive their energy from their prey, merely nutrients. Especially nitrogen.

The really cool thing about carnivorous plants (aside from the fact that they hunt and devour prey) is the variety of hunting mechanisms they employ. Some of these traps are more complicated than a spy-movie death apparatus. Here are some of the amazing techniques carnivorous plants use to get their fill. [Image courtesy of Playbill.com.]

Pitcher and Pitfall Plants

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Have you have ever had the misfortune of finding an insect flailing around in a glass of your sugary beverage of choice? That's the basic mechanism employed by a pitcher plant. They entice prey into their rolled leaf cavities with the lure of bright pigments and nectar at the bottom of a deep, inescapable pit. The insects are intoxicated by (and then drown in) this liquid, which contains bacteria and enzymes that will eventually dissolve their carcasses. The inner tubes utilize a slippery, hairy or grooved surface to make sure even sober insects can't escape. Forget about rainwater filling the cavity and diluting the digestive juices; most pitcher plants use some sort of umbrella-like contraption to keep water out, usually a flared leaf called an operculum. [Image courtesy of PitcherPlant.org.]

Snap Traps

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In this amazing trap, the convex leaves are covered in triggers that slam shut and become concave when they sense an insect has arrived. Once shut, the lobes of the leaves are stimulated by the struggling insect and grow together to form a stomach. The glands then secrete an enzyme that digests the insect in about ten days. The ever-famous Venus Flytrap is the best example of this vicious hunting style, and there are very few other species that use this technique.

The undirected movement of the leaves in response to touch snapping is a process called thigmonasty (which sounds like a great DJ moniker to me). Just how fast is the process? Well, the Venus Flytrap can close its traps within 100 milliseconds. After digestion, the leaves re-open and can capture another victim, though it's rare for a single trap to catch more than three insects in its lifetime. Each plant has multiple traps, so it never goes hungry. [Image courtesy of MooseysCountryGarden.com.]

Here's a YouTube demonstration:

Bladder and Suction Traps

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I don't particularly like the words bladder or suction, especially when paired with the word trap, but this trap type is incredible. These plants live in the water and use lots of tiny bladders to ensnare dinner. Basically, bladder traps pump ions out from their interiors and use osmosis to create a partial vacuum. If a creature triggers the trap, it is immediately sucked in, along with a bunch of extra water. The plant immediately begins to filter out the water and digest the prey, and it can hunt for more prey as it digests its current catch.

These complicated traps are exclusive to bladderwort plants, which have at least 215 species. Unlike other carnivorous plants, which exclusively eat insects, bladderworts trap water fleas, nematodes, mosquito larvae, small tadpoles and other things you don't want in your swimming water. Despite their gross-looking traps, bladderworts have beautiful flowers that are similar to orchids and snapdragons, only smaller. [Image courtesy of Carnivorous Plants Online.]

Flypaper Traps

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Just as the name indicates, these plants generate super-sticky glue called mucilage to trap insects. Plants cover their attractive leaves with mucilage, which resemble droplets of fresh dew or rain, and then wait for an insect to land, and fall right into their trap.

Sundew plants are a common but fascinating example of these types of plants. Sure, the name sounds warm and pleasant, but it actually refers to the glistening drops of mucilage at the tip of each tentacle that resemble drops of morning dew. Tentacles and mucilage, gross. Once an insect adheres to the plant, the tentacles very slowly move to wrap around and eventually digest the prey.

The butterwort group of carnivorous plants uses broader leaves rather than tentacles to attract prey. The huge, brightly colored leaves are completely covered in mucilage. Once an insect lands on a leaf, the plant creates more mucilage, causing the struggling insect to become encased in the sticky stuff. Other glands on the leaf secrete digestive juices, and the nutrients are absorbed by the plant leaves. [Image courtesy of Wikipedia.]

Lobster-pot Traps

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Think of these plants as the Roach Motels of carnivorous plants: insects check in, but they don't check out. The traps are easy and intriguing to enter, but very difficult to escape due to inward-pointing bristles and spiraling parts. The genlisea group of plants uses traps that have all their carnivorous parts beneath the soil. The trap is basically a pair of thin tubes joined in an inverted 'V' shape, with spiral grooves down their lengths that allow the entrance of soil-dwelling invertebrates. The grooves are lined with inward-pointing hairs that prevent the prey from escaping and instead force them into the apex of the 'V,' where they are slowly digested. [Image courtesy of CarnivorousPlants.org.]

Caroline Donnelly is an occasional contributor to mentalfloss.com. Her last story looked at 7 Famous Phrases Famous People Own.

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iStock // Ekaterina Minaeva
technology
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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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Stephen Missal
crime
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New Evidence Emerges in Norway’s Most Famous Unsolved Murder Case
May 22, 2017
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A 2016 sketch by a forensic artist of the Isdal Woman
Stephen Missal

For almost 50 years, Norwegian investigators have been baffled by the case of the “Isdal Woman,” whose burned corpse was found in a valley outside the city of Bergen in 1970. Most of her face and hair had been burned off and the labels in her clothes had been removed. The police investigation eventually led to a pair of suitcases stuffed with wigs and the discovery that the woman had stayed at numerous hotels around Norway under different aliases. Still, the police eventually ruled it a suicide.

Almost five decades later, the Norwegian public broadcaster NRK has launched a new investigation into the case, working with police to help track down her identity. And it is already yielding results. The BBC reports that forensic analysis of the woman’s teeth show that she was from a region along the French-German border.

In 1970, hikers discovered the Isdal Woman’s body, burned and lying on a remote slope surrounded by an umbrella, melted plastic bottles, what may have been a passport cover, and more. Her clothes and possessions were scraped clean of any kind of identifying marks or labels. Later, the police found that she left two suitcases at the Bergen train station, containing sunglasses with her fingerprints on the lenses, a hairbrush, a prescription bottle of eczema cream, several wigs, and glasses with clear lenses. Again, all labels and other identifying marks had been removed, even from the prescription cream. A notepad found inside was filled with handwritten letters that looked like a code. A shopping bag led police to a shoe store, where, finally, an employee remembered selling rubber boots just like the ones found on the woman’s body.

Eventually, the police discovered that she had stayed in different hotels all over the country under different names, which would have required passports under several different aliases. This strongly suggests that she was a spy. Though she was both burned alive and had a stomach full of undigested sleeping pills, the police eventually ruled the death a suicide, unable to track down any evidence that they could tie to her murder.

But some of the forensic data that can help solve her case still exists. The Isdal Woman’s jaw was preserved in a forensic archive, allowing researchers from the University of Canberra in Australia to use isotopic analysis to figure out where she came from, based on the chemical traces left on her teeth while she was growing up. It’s the first time this technique has been used in a Norwegian criminal investigation.

The isotopic analysis was so effective that the researchers can tell that she probably grew up in eastern or central Europe, then moved west toward France during her adolescence, possibly just before or during World War II. Previous studies of her handwriting have indicated that she learned to write in France or in another French-speaking country.

Narrowing down the woman’s origins to such a specific region could help find someone who knew her, or reports of missing women who matched her description. The case is still a long way from solved, but the search is now much narrower than it had been in the mystery's long history.

[h/t BBC]

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