10 Juicy Facts About Leeches

Ian Cook
Ian Cook

Leeches get a bad rap, but they’re actually pretty cool once you get to know them—and we're finding out more about them, even today. Recently, a team led by Anna Phillips, curator of parasitic worms at the Smithsonian National Museum of Natural History, discovered a new species of medicinal leech (pictured above) in a Maryland swamp. We asked parasite expert and curator at the American Museum of Natural History Mark E. Siddall to share some surprising facts about the worms we love to hate. 

1. Not all leeches suck blood.

Hematophagous, or blood-feeding, species are only one type of leech. “The vast majority of species are [hematophagous],” Siddall tells Mental Floss, “but it depends on the environment. In North America, there are probably more freshwater leeches that don’t feed on blood than there are blood-feeders.” And even among the hematophagous species, there are not too many who are after you. “Very few of them are interested in feeding on human blood,” Siddall says. “Certainly they’ll do it, if they’re given the opportunity, but they’re not what they’re spending most of their time feeding on.” 

2. Leeches are everywhere.

Japanese leech on a log
Pieria, Wikimedia Commons // Public Domain

“Every continent on the planet has leeches, with the exception of Antarctica,” Siddall says. “And even then there are marine leeches in Antarctic waters.” Humans have co-existed with leeches for so long, according to Siddall, that just about every language has a word for leech. 

3. Leeches have made a comeback in medicine.

Bloodletting for bloodletting’s sake has fallen out of favor with Western physicians, but that doesn’t mean medicinal leeches are enjoying a cushy retirement. Today, surgeons keep them on hand in the operating room and use them as mini-vacuums to clean up blood. “That is a perfectly sensible use of leeches,” Siddall says. Other uses, though, are less sensible: “The more naturopathic application of leeches in order to get rid of bad blood or to cure, I don’t know, whatever happens to ail you, is complete hooey,” he says. How on Earth would leeches take away bad blood and leave good blood? It’s silly.” 

4. Novelist Amy Tan has her own species of leeches.

Land-based leeches made an appearance in Tan’s 2005 book Saving Fish from Drowning, a fact that instantly put the author in leech researchers’ good graces. “There are not a lot of novels out there with terrestrial leeches in them,” Siddall says. So when he and his colleagues identified a new species of tiny terrestrial leeches, they gave the leech Tan’s name. The author loved it. “I am thrilled to be immortalized as Chtonobdella tanae,” Tan said in a press statement. “I am now planning my trip to Queensland, Australia, where I hope to take leisurely walks through the jungle, accompanied by a dozen or so of my namesake feeding on my ankles.”

5. Leeches can get pretty big.

The giant Amazon leech (Haementeria ghilianii) can grow up to 18 inches and live up to 20 years. And yes, this one’s a blood-feeder. Like all hematophagous species, H. ghilianii sticks its proboscis (which can be up to 6 inches long) into a host, drinks its fill, and falls off. Scientists thought the species was extinct until a zoologist found two specimens in the 1970s, one of whom he named Grandma Moses. We are not making this up.

6. Leeches make good bait.

Many walleye anglers swear by leeches. “A leech on any presentation moves more than other types of live bait," pro fisher Jerry Hein told Fishing League Worldwide. "I grew up fishing them, and I think they're the most effective live bait around no matter where you go." There’s an entire leech industry to provide fishers with their bait. One year, weather conditions kept the leeches from showing up in their typical habitats, which prevented their collection and sale. Speaking to CBS news, one tackle shop owner called the absence of leeches “the worst nightmare in the bait industry.”

7. Leech scientists use themselves as bait.

Siddall and his colleagues collect and study wild leeches. That means hours of trekking through leech territory, looking for specimens. “Whether we’re wandering in water or traipsing through a bamboo forest,” Siddall says, “we are relying on the fact that leeches are attracted to us.” Do the leeches feed on them? “Oh my god, yes. We try to get them before they feed on us … but sometimes, obviously, you can’t help it.”

8. Leech sex is mesmerizing.

Like many worms, leeches are all hermaphroditic. The specifics of mating vary by species, but most twine themselves together and trade sperm packets. (The two leeches in the video above are both named Norbert.)

9. Some leech species make surprisingly caring parents. 

“There’s a whole family of leeches that, when they lay their eggs, will cover them with their own bodies,” Siddall says. “They’ll lay the eggs, cover them with their bodies, and fan the eggs to prevent fungus or bacteria from getting on them, and then when the eggs hatch, they will attach to the parent. They’re not feeding on the parent, just hanging on, and then when the parent leech goes to its next blood meal it’s carrying its offspring to its next blood meal. That’s pretty profound parental care, especially for invertebrates.”

10. You might be the next to discover a new leech species. 

Despite living side-by-side with leeches for thousands of years, we’ve still got a lot to learn about them. Scientists are aware of about 700 different species, but they know there are many more out there. “I’ll tell you what I wish for,” Siddall says. “If you ever get fed on by a leech, rather than tearing off and burning it and throwing it in the trash, maybe observe it and see if you can see any color patterns. Understand that there’s a real possibility that it could be a new species. So watch them, let them finish. They’re not gonna take much blood. And who knows? It could be scientifically useful.”

‘Soft and Cuddly’ Venomous Puss Caterpillars Have Been Spotted in at Least 3 States

Wayne W G, Flickr // CC BY-NC 2.0
Wayne W G, Flickr // CC BY-NC 2.0

The puss caterpillar is cute, cuddly, and coming to ruin your day.

USA Today reports that the highly venomous creature, also known as the southern flannel moth caterpillar, or asp, has recently been spotted in Florida, Texas, and South Carolina. Underneath its furry coat are tiny, potent spines that break off and attach themselves to your skin, causing excruciating pain and creating a hematoma, a bruise-like wound under your skin where blood has leaked from blood vessels.

According to University of Connecticut entomologist David Wagner, the caterpillar is dangerous partly because the sting of those spines becomes more painful over time. “It builds for a long time in a frightening way. No one expects stings to gain in impact or discomfort, and these will,” he told USA Today. “It packs quite a wallop.”

For one victim in Dade City, Florida, even medically administered morphine didn’t alleviate her agony. “It felt like someone was drilling into my bones,” she wrote in a Facebook post. “I cried and pleaded with God for hours to make it stop.”

puss caterpillar
going on going on, Flickr // CC BY-NC 2.0

If one does happen to inch its way onto you, curb the instinct to flail about or swat at random—trying to brush off the adorable nightmare just increases the possibility of those sinister spines sticking to your skin. Instead, have someone carefully and calmly remove the insect with a twig or a 39-and-a-half-foot pole. Then, take a shower and wash your clothes to minimize further exposure to leftover spines.

As traumatizing as the experience sounds, your chances of meeting one of these fun-sized villains are hearteningly slim. Wagner explains that they’re particularly scarce above the Mason-Dixon line, and not even very common in southern states, where they’re usually spotted.

In short, this is just another scientific reason why you should stick to petting dogs.

[h/t USA Today]

8 Adorable Products You Can Buy for International Sloth Day

Good Luck Socks/Intelex via Amazon
Good Luck Socks/Intelex via Amazon

It’s that time of the year again, folks—the time when we all collectively lose our chill over a slow-moving, two- or three-toed mammal with an adorable squeak and poop that defies physics. That’s right: International Sloth Day is coming on October 20. Here’s a list of must-have coloring books, onesies, and Christmas sweaters that you can pick up to showcase your love of one of the internet's favorite animals.

1. Cuddly Microwaveable Sloth; $23

Microwavable sloth for International Sloth Day.
Intelex/Amazon

Warm your heart and your body with a plush sloth that doubles as a soothing heating pad. The toy is filled with millet grains and dried French lavender, a combination intended to help you get to sleep easier.

Buy it: Amazon

2. Hanging Ceramic Sloth Planter; $19

FattyBee Ceramic Sloth Planter.
FattyBee/Amazon

This flower planter pulls double duty, communicating both your love of sloths and your appreciation for plants. And it makes a tasteful piece of hanging home decor, too.

Buy it: Amazon

3. Sloth Coloring Book; $7

Sloth Coloring Book on Amazon.
CreateSpace Independent Publishing Platform/Amazon

Sloths themselves are already works of art, but you’d be forgiven for wanting a few more sloth-related crafts in your life. Now you can make your own masterpiece with this detailed coloring book. All you'll need are some colored pencils and you'll be ready to go.

Buy it: Amazon

4. Farting Sloth Coloring Book; $7

Sloth Farts Coloring Book on Amazon.
M & L Coloring Books/Amazon

But maybe traditional coloring books aren’t your thing. You’re in luck: Amazon sells a coloring book for the crowd that both loves sloths and laughs a little too much at farts.

Buy it: Amazon

5. Sloth Socks; $14

Sloth Socks on Amazon.
Good Luck Socks/Amazon

These socks are ideal for people who might not want to wear their love of sloths out in the open but are very comfortable showing it off on their ankles.

Buy it: Amazon

6. Sloth Onesie; $60

Tipsy Elves Sloth Onesie on Amazon.
Tipsy Elves/Amazon

No list of sloth-related products would be complete without a cozy onesie, and this one from Tipsy Elves is perfect for either pajamas or a last-minute Halloween costume. This onesie even comes with zippered pockets and cuddly sloth claws!

Buy it: Amazon

7. Sloth-Themed Ugly Christmas Sweater; $45


Tipsy Elves/Amazon

Why not celebrate the upcoming holiday season with this sloth-themed ugly Christmas sweater? You’re sure to be the hit of any holiday pub crawl or office Christmas party.

Buy it: Amazon

8. Sloth Mug; $13


Mika Mugs/Amazon

Really, what says it better than this mug? You just really freaking love sloths, and there’s nothing wrong with that, so be sure to declare your feelings along with your morning cup of coffee.

Buy it: Amazon

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