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4 Parasites We Wouldn't Mind Hosting, After All

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It's parasites week here at mental_floss, which we kicked off two days ago with the release of our newest video, "Attack of the Parasites." Now, while it's true that there are all kinds of compelling reasons to avoid becoming infested with parasites -- especially by the kinds that cause things like river blindness and elephantiasis of the genitalia -- there are also a few reasons to make nice with our tiny, opportunistic compatriots. Here are four.

1. Pseudacteon, the "decapitating fly"

Nobody likes fire ants. Where I grew up in Southern Florida, they were a major nemesis to unfettered, shoeless outdoor romping; one false step could mean a foot covered in biting, welt-inducing fire ants. In fact, ever since they were accidentally imported from South America via cargo ship in the 1930s, they've spread like an annoying, predator-less plague from coast to coast, infesting at least 18 states. So far, the only measures introduced to deal with them have been stopgap at best -- sprinkling poison on the mounds, for instance. That is, until now.

ant1.gifMeet Pseudacteon, a parasitic fly from South America. Pseudacteon, like most living creatures, loves to reproduce. The important distinction between it and other flies, however, is where Pseudacteon lays its eggs: inside the heads of fire ants. Get ready for an awesomely grody cycle-of-life: the larvae develop by feeding on the muscle and nervous tissue in the head. After about two weeks, they cause the ant's head to fall off by releasing an enzyme that dissolves the membrane attaching the ant's head to its body. The fly pupates in the detached head capsule (pictured above!). Hence: the decapitating fly! Currently, industrious agricultural scholars are importing them from South America in the hopes that they'll do rid us of our fire ants. Godspeed, little decapitators.

2. Worm therapy

A rare bit of good news from the world of gastrointestinal maladies: swallowing the eggs of a certain type of parasite worm may actually help cure Crohn's disease. The basic theory is this: in countries where people's exposure to parasites is high, disorders of the immune system like Crohn's, multiple sclerosis and type 1 diabetes are rare. In ultra-sanitized industrialized nations like the U.S., they're common. According to researchers, we may have hygiened our way into a few diseases that certain types of parasites actually help prevent, and by re-introducing them into the body -- that is, with "worm therapy" -- we may actually be able to combat those conditions.

Specifically, treatment with the eggs of the intestinal parasite helminth Trichuris suis may be a safe and effective treatment for Crohn's disease, according to the results of a small, preliminary trial conducted at the University of Iowa in Iowa City. T. suis is not a natural human parasite, but primarily affects pigs.

3. The blepharipa schineri fly

cat2.jpgIf swallowing worm eggs isn't your thing, then maybe you can get behind this: the fuzzy, half-inch-long blepharipa schineri does for the gypsy moth what the decapitating fly does for the fire ant. (Well, it doesn't actually decapitate the moth, but the end result is the same: no more moths. It achieves this by laying eggs in pre-moth gypsy caterpillars, where they hatch and prevent them from growing into moths.)

What's so terrible about gypsy moths? Just ask a park ranger: gypsy moths eat the leaves of some of our most popular shrubs and trees, from oak to beech to poplars. In the Eastern U.S., the moths are well-established over at least 60 million acres, defoliating and killing hundreds of varieties of trees. If you don't like the sound of that, you just might like the sound of what the fly does to the moth:

A parasite of the gypsy moth, the B. schineri fly kills unlucky gypsy moth caterpillars that accidentally eat fly eggs while munching on leaves. A gray-black speck about the size of a thumbtack point, the fly egg hatches inside the caterpillar's stomach. The transparent B. schineri maggot that emerges will later poke holes in the caterpillar's gut, then wriggle its way to the nerve cord that runs the length of the body. While the gypsy moth caterpillar transforms into a pupa--a pre-moth that slumbers in a silky, loosely woven cradle--the B. schineri maggot feeds on the host's innards, slowly killing it.

Gross? Sure. Useful? Definitely. Lucky for us, moths are this fly's only breeding ground.

4. It Makes the Ladies Happy

Quite literally: the Toxoplasma parasite, found primarily in cat feces, is known to have a mood-altering effect on humans, which differs depending on the sex of the human. In a study conducted by parasitologist Jaroslav Flegr of Charles University in Prague, some infected women were likely to become more outgoing and warm-hearted, whereas some infected men became more jealous and suspicious. (Not everyone is mood-altered by cat poo; it's a small, though statistically significant, percentage.) When it's not changing our moods, the Toxoplasma is trying to spread itself by making rats who come into contact with it act fearless, which makes it easier for them to be caught by cats (who then become infected, etc).

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Animals
25 Benefits of Adopting a Rescue Dog
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According to the ASPCA, 3.3 million dogs enter shelters each year in the United States. Although that number has gone down since 2011 (from 3.9 million) there are still millions of dogs waiting in shelters for a forever home. October is Adopt a Shelter Dog Month; here are 25 benefits of adopting a shelter dog.

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How Urban Legends Like 'The Licked Hand' Are Born
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If you compare the scary stories you heard as a kid with those of your friends—even those who grew up across the country from you—you’ll probably hear some familiar tales. Maybe you tried to summon Bloody Mary by chanting her name in front of the mirror three times in a dark bathroom. Maybe you learned never to wonder what’s under a woman’s neck ribbon. Maybe you heard the one about the girl who feels her dog lick her hand in the middle of the night, only to wake up to find him hanging dead from the shower nozzle, the words “humans can lick too” written on the wall in the dog’s blood.

These ubiquitous, spooky folk tales exist everywhere, and a lot of them take surprisingly similar forms. How does a single story like the one often called “Humans Can Lick Too” or "The Licked Hand" make its way into every slumber party in America? Thrillist recently investigated the question with a few experts, finding that most of these stories have very deep roots.

In the case of The Licked Hand, its origins go back more than a century. In the 1990s, Snopes found that a similar motif dates back to an Englishman’s diary entry from 1871. In it, the diary keeper, Dearman Birchall, retold a story he heard at a party of a man whose wife woke him up in the middle of the night, urging him to go investigate what sounded like burglars in their home. He told his wife that it was only the dog, reaching out his hand. He felt the dog lick his hand … but in the morning, all his valuables were gone: He had clearly been robbed.

A similar theme shows up in the short story “The Diary of Mr. Poynter,” published in 1919 by M.R. James. In it, a character dozes off in an armchair, and thinks that he is petting his dog. It turns out, it’s some kind of hairy human figure that he flees from. The story seems to have evolved from there into its presently popular form, picking up steam in the 1960s. As with any folk tale, its exact form changes depending on the teller: sometimes the main character is an old lady, other times it’s a young girl.

You’ll probably hear these stories in the context of happening to a “friend of a friend,” making you more likely to believe the tale. It practically happened to someone you know! Kind of! The setting, too, is probably somewhere nearby. It might be in your neighborhood, or down by the local railroad tracks.

Thrillist spoke to Dr. Joseph Stubbersfield, a researcher in the UK who studies urban legends, who says the kind of stories that spread widely contain both social information and emotional resonance. Meaning they contain a message—you never know who’s lurking in your house—and are evocative.

If something is super scary or gross, you want to share it. Stories tend to warn against something: A study of English-language urban legends circulating online found that most warned listeners about the hazards of life (poisonous plants, dangerous animals, dangerous humans) rather than any kind of opportunities. We like to warn each other of the dangers that could be lurking around every corner, which makes sense considering our proven propensity to focus on and learn from negative information. And yes, that means telling each other to watch out for who’s licking our hands in the middle of the night.

Just something to keep in mind as you eagerly await Jezebel’s annual scary story contest.

[h/t Thrillist]

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