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Four Different Species Use the Same Odor to Exploit Each Other

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Wikimedia Commons

Chemical warfare. Hijacked communications. Stowaways. Eavesdropping. Sounds like the makings of a spy movie, but it’s just another day in nature. 

Plants have got to be fighters in this big bad world. When an animal that wants to eat them comes along to start chowing down, they can’t run or hide. They’ve got to fight back. Some of them have structural defenses like thorns or spines or nettles that jab at herbivores’ mouths. Some have waxy exteriors that make them too slippery for insects to land on, or produce resins and saps that create a sticky trap for bugs.

Others wage chemical warfare, sometimes in a roundabout way. Methyl salicylate (MeSA), also known as wintergreen oil, is produced by some plants when they’re damaged by herbivorous insects. The chemical doesn’t harm the insects directly, but acts like a mayday signal that attracts predatory bugs that come and eat the herbivores. In one case that University of Florida scientists have recently described, it’s also at the center of a web of species trying to exploit each other.

When citrus trees are damaged and release MeSA, it not only attracts helpful bugs, but also a jumping plant louse known as the Asian citrus psyllid (Diaphorina citri, top). The psyllids follow the chemical’s odor because a tree that’s already damaged is a good place to find food, places to lay eggs (which the psyllids can only do in new citrus shoots) and other bugs to mate with. 

Sometimes, though, there’s no meal to be had, because the tree has been infected by a bacterium called Candidatus Liberibacter asiaticus (Las). The psyllids are the bacterium’s primary vector for spreading from tree to tree. When Las infects a tree, it lowers the tree’s nutritional quality and also hijacks its odor production, forcing it to release MeSA as bait. When the psyllids show up and find there’s no less-than-ideal food, they move on in search of another tree—but not before the bacteria cling to them and hitch a ride to their next victim.

A group of entomologists in Florida, led by Xavier Martini, recently found that the trees, lice, and bacteria aren’t using these chemical signals in private, and that there’s another creature eavesdropping on them. The same odor that the lice use to find food, and that the bacteria exploit to lure the lice, also attracts a wasp called Tamarixia radiata. These parasites feed on the bodily fluids of citrus psyllids and also lay their eggs on the undersides of the immature insects. When the eggs hatch, the larvae attach to the psyllid and feed on their hemolymph (kind of the arthropod version of blood) until the host dies. Then, they crawl inside the mummified psyllids, where they’ll develop into adults and eventually break their way back out through the thorax or head. 

Martini and his team discovered that the wasps “eavesdrop” on the chemical cues produced by citrus trees to find their hosts, and were more attracted to the MeSA from Las-infected trees than non-infected trees. At trees where the bacteria was present, the wasps also parasitized five times as many psyllids as they did at the regular trees. 

That the wasps are attracted to the same chemical as the psyllids potentially complicates things for the Las bacteria. Martini found that the wasps sometimes arrive at an infected tree before the psyllids show up, which might drive them away or result in them being killed or parasitized before they can give the bacteria a lift to another tree. Then again, when the wasps show up after psyllids they might actually help the bacteria by causing the psyllids to disperse far and wide, which is exactly what the bacteria need to spread. 

A tree’s “cry for help” not only attracts more danger, but can also be hijacked by bacteria to help them spread infection, while an eavesdropping parasite uses the same odor to find a host that its children turn into a macabre nursery. Ain’t nature grand? 

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iStock // Ekaterina Minaeva
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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Opening Ceremony
These $425 Jeans Can Turn Into Jorts
May 19, 2017
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Opening Ceremony

Modular clothing used to consist of something simple, like a reversible jacket. Today, it’s a $425 pair of detachable jeans.

Apparel retailer Opening Ceremony recently debuted a pair of “2 in 1 Y/Project” trousers that look fairly peculiar. The legs are held to the crotch by a pair of loops, creating a disjointed C-3PO effect. Undo the loops and you can now remove the legs entirely, leaving a pair of jean shorts in their wake. The result goes from this:


Opening Ceremony

To this:


Opening Ceremony

The company also offers a slightly different cut with button tabs in black for $460. If these aren’t audacious enough for you, the Y/Project line includes jumpsuits with removable legs and garter-equipped jeans.

[h/t Mashable]