What Happens When a Fly Lands on Your Food?

iStock
iStock

"Waiter, what's this fly doing in my soup?"
"Transmitting bacteria, sir."

This gross response doesn't make a great punchline (nor will it earn anybody a big tip), but it is the truth. But why is that fly just sitting—or swimming—there? And is the soup still safe to eat? If you really want to know, gird yourself and read on.

The common house fly (Musca domestica) has no venom, no stinger, and no fangs. It finds its food in a peaceful way—by rolling around in other animals' waste and garbage. With no teeth, the fly requires a liquid diet. This would be a problem, since a lot of food is solid, but the fly has a disgusting workaround: It spits and pukes on its meal. Compounds in its saliva and bile break down the food, making it as slurpable as a smoothie.

As the fly eats, it's usually also pooping—and if it's female, possibly laying eggs as well. Flies really are an absolute bonanza of disgustingness.

All of this would be gross, but ultimately harmless, if flies only ate soup. But they're opportunists. They eat rotting garbage and they eat animal feces, and in doing so they consume loads of pathogens.

"House flies are the movers of any disgusting pathogenic microorganism you can think of," Jeff Scott, an entomologist at Cornell University, told the Daily Mail. "Anything that comes out of an animal, such as bacteria and viruses, house flies can take from that waste and deposit on your sandwich."

Experts estimate that adult houseflies can transmit more than 100 different diseases and parasites, from Salmonella and tuberculosis to tapeworms.

Does this mean we should immediately throw out any food a fly has touched? Probably.

According to research initiated at Penn State Eberly College of Science and in collaboration with the Nanyang Technological University in Singapore and other international institutions , houseflies tend to harbor pathogens on their legs, meaning even a brief touchdown on your tuna melt could very conceivably transmit any number of worrisome bacteria in an instant. It's better to keep picnic foods sealed until they're needed or to ask for a new dish if your local restaurant has any unsolicited, winged guests lurking around. 

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What Makes Dogs Tilt Their Heads?

iStock.com/JoeChristensen
iStock.com/JoeChristensen

By tilting its head slightly to the side, a dog can melt the heart of even the most hardened cat person. Most everyone finds this behavior adorable, but few people can explain what compels a dog to do it. Are dogs somehow aware of the effect they have on humans, using a cute trick to exploit us for affection?

Experts say the real answer has more to do with your dog's ability to empathize. Dogs are impressively good at reading and responding to our body language and vocal cues. When you're lecturing your pooch for taking food off the counter, they're taking it all in even if the literal message gets lost in translation. Same goes for when you’re giving your pup praise. Dogs are capable of recognizing certain parts of human language, so when they cock their heads as you speak to them, it's possible they're listening for specific words and inflections they associate with fun activities like meals and playtime.

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The head-tilt may also have something to do with how the canine ear is constructed. Even though dogs sense frequencies humans are incapable of hearing, their ability to detect the source of sounds is less precise than ours. A dog's brain calculates extremely minuscule differences between the time it takes a sound to reach each ear, so a simple change in head position could provide them with useful sensory information. When dogs tilt their heads, some experts believe they are adjusting their pinnae, or outer ears, in order to better pinpoint the location of a noise.

Stanley Coren of Psychology Today believes that vision also has something to do with this behavior. If you try holding your fist in front of your nose, you can get a fair sense of what it’s like to view the world with a muzzle. When watching someone speak, the "muzzle" will block the lower part of their face from view, and if you tilt your head to one side you will be able to see it more clearly. In addition to being able to perceive emotional cues in our voices, dog can also read our facial expressions. When cocking their heads to the side, Coren suggests that dogs are trying to get a better view of our mouths, where our most expressive facial cues originate.

If your dog is a frequent head-tilter, this could mean that they're especially empathetic. Some experts have reported that dogs who are more socially apprehensive are less likely to tilt their heads when spoken to. But if your dog doesn't display this behavior, there's no need to automatically label them as a canine sociopath (especially if they have pointy ears or a flatter snout). And even if the head tilt does come from instinct, the more owners respond to it with positive reinforcement, the more likely dogs are to do it in search of praise.

Have you got a Big Question you'd like us to answer? If so, send it to bigquestions@mentalfloss.com.

Where Did the Phrase 'Red Herring' Come From?

iStock.com/Mathias Darmell
iStock.com/Mathias Darmell

You may have seen a red herring in a recent book or movie, but you probably only realized it after the fact. These misleading clues are designed to trick you into drawing an incorrect conclusion, and they're a popular ploy among storytellers of all stripes.

If you've seen or read the Harry Potter series—and really, who hasn’t?—then you may recall some of the many instances where J.K. Rowling employed this literary device. That endearing plot twist about the nature of Snape's character, for example, is likely one of the longest-running red herrings ever written.

Sometimes they aren't even subtle. Agatha Christie's murder mystery And Then There Were None directly mentions red herring in reference to a character's death, and a statue of a red herring appears in Lemony Snicket's A Series of Unfortunate Events. Perhaps most blatantly, a character in the cartoon A Pup Named Scooby-Doo who was constantly being blamed for myriad crimes was named—you guessed it—Red Herring.

But where does this literary device come from, and why is it named after a fish? For a bit of background: herring are naturally a silvery hue, but they turn reddish-brown when they're smoked. Long before refrigerators were invented, this was done to preserve the fish for months at a time. They can also be pretty smelly. As Gizmodo's io9 blog points out, it was believed that red herring were dragged against the ground to help train hounds to sniff out prey in the 17th century. Another theory was that escaped prisoners used the fish to cover their tracks and confuse the dogs that tailed them.

However, io9 notes that red herring were actually used to train horses rather than dogs, and only if the preferred choice—a dead cat—wasn't available. The idea was that the horses would get used to following the scent trail, which in turn would make them less likely to get spooked while "following the hounds amid the noise and bustle of a fox hunt," notes British etymologist and writer Michael Quinion, who researched the origin of the phrase red herring.

The actual origin of the figurative sense of the phrase can be traced back to the early 1800s. Around this time, English journalist William Cobbett wrote a presumably fictional story about how he had used red herring as a boy to throw hounds off the scent of a hare. He elaborated on this anecdote and used it to criticize some of his fellow journalists. "He used the story as a metaphor to decry the press, which had allowed itself to be misled by false information about a supposed defeat of Napoleon," Quinion writes in a blog. "This caused them to take their attention off important domestic matters."

According to Quinion, an extended version of this story was printed in 1833, and the idiom spread from there. Although many people are more familiar with red herrings in pop culture, they also crop up in political spheres and debates of all kinds. Robert J. Gula, the author of Nonsense: Red Herrings, Straw Men and Sacred Cows: How We Abuse Logic in Our Everyday Language, defines a red herring as "a detail or remark inserted into a discussion, either intentionally or unintentionally, that sidetracks the discussion."

The goal is to distract the listener or opponent from the original topic, and it's considered a type of flawed reasoning—or, more fancifully, a logical fallacy. This application of red herring seems to be more in line with its original usage, but as Quinion notes: "This does nothing to change the sense of red herring, of course: it's been for too long a fixed part of our vocabulary for it to change. But at least we now know its origin. Another obscure etymology has been nailed down."

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