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.”

Massive Swarms of Migrating Dragonflies Are So Large They’re Popping Up on Weather Radar

emprised/iStock via Getty Images
emprised/iStock via Getty Images

What do Virginia, Pennsylvania, Indiana, and Ohio all have in common? Epic swarms of dragonflies, among other things.

WSLS-TV reports that this week, weather radar registered what might first appear to be late summer rain showers. Instead, the green blotches turned out to be swarms of dragonflies—possibly green darners, a type of dragonfly that migrates south during the fall.

Norman Johnson, a professor of entomology at The Ohio State University, told CNN that although these swarms happen occasionally, they’re definitely not a regular occurrence. He thinks the dragonflies, which usually prefer to travel alone, may form packs based on certain weather conditions. If that sounds vague, it’s because it is: Johnson said that entomologists haven’t worked out all the details when it comes to dragonfly migration. They do know that the airborne insects cover an average of eight miles per day, while some overachievers can fly as far as 86.

Based on the radar footage shared by the National Weather Service’s Cleveland Office, the dragonfly clouds seem almost menacing. But, while swarms of any insect species aren’t exactly delightful, these creatures are both harmless and surprisingly beautiful, at least up close. Anna Barnett, a resident of Jeromesville, Ohio, even told CNN that witnessing the natural phenomenon was “amazing!”

Amazing as it may be to see, it’s hard to hear news about unpredictable animal behavior without wondering if it’s related in some way to Earth’s rising temperatures. After all, climate change has already affected wasps in Alabama, polar bears in Russia, and no doubt countless other animal species around the world.

[h/t WSLW-TV]

6 Fall Festivals Around the World That Celebrate Animals

Prakash Mathema, AFP/Getty Images
Prakash Mathema, AFP/Getty Images

Where would humans be without animals? Chickens and cows give us eggs and milk, providing nourishment (and also cake). Horses, donkeys, and water buffalo are as hardworking as any person, and thanks to our pets, we always have a source of love and entertainment to come home to. It's time we celebrate animals more often, and to get you started, here are six fall festivals around the world that do just that.

1. Kukur Tihar

Dog in Nepal during a fall festival
Tuayai/iStock via Getty Images

A big part of Tihar, a five-day Hindu festival held in late autumn in Nepal, is giving thanks to other species. Crows, believed to be the messengers of death, are worshipped on the first day. Cows are worshipped on the third, and often oxen on the fourth. The second day, though, is all about man's best friend. Dogs are described favorably in Hindu religious texts, and it’s believed that they can warn people of impending danger and even death. In a ceremony called Kukur Tihar, people place flower garlands around the necks of both pet dogs and stray dogs to show their respect. A red dot (tika) is placed on their foreheads in an act of worship, and naturally, the dogs are spoiled with lots and lots of treats.

2. Transhumance Festival

Hundreds of sheep in the street
Pierre Philippe Marcou, AFP/Getty Images

In Spanish, this festival in Madrid is called Fiesta de la Trashumancia. The word transhumance refers to the act of moving herds of livestock to different grazing grounds depending on the season. In practice, it's quite the spectacle. Thousands of sheep have been led through the streets of Madrid each autumn since the festival was formally established in 1994. Men and women in traditional garb lead the way, singing and dancing along the parade route in celebration of centuries-old shepherding traditions.

3. Monkey Buffet Festival

A monkey eating various kinds of fruit
Saeed Khan, AFP/Getty Images

Visitors to Thailand’s temples are advised not to feed the monkeys (they can get awfully handsy), but the locals of Lopburi make an exception on the last Sunday of November. On this day, towers of fruit and banquet tables containing several tons of food and even cans of Coca-Cola are set up in the ruins of a 13th-century temple. Once a sheet is removed to unveil the spread, it doesn’t take long for Lopburi’s thousands of macaques to arrive. Thailand's reverence for monkeys dates back some 2000 years to legends surrounding the monkey king Hanuman and his heroic feats. Nowadays, the creatures are considered a sign of good luck in the country.

4. Woolly Worm Festival

The woolly worm is to Banner Elk, North Carolina, what the groundhog is to Punxsutawney, Pennsylvania. According to local folklore, the color of this fuzzy caterpillar can be analyzed in autumn to predict how severe the forthcoming winter will be. The 13 segments on its body are thought to correspond to the 13 weeks of winter—more black means colder weather and snow, while more brown means the weather will be fair. To make this prognostication process more official, the Woolly Worm Festival was established on the third weekend of October in 1978. This year, it will be held October 20-21. A worm race is the main event, and the caterpillar that climbs the fastest up three feet of string gets the honor of helping to predict the winter (plus a $1000 cash prize for the worm’s coach). “Patsy Climb” and “Dale Wormhardt” were a couple of past competitors.

5. Pushkar Camel Fair

Decorated camels
Roberto Schmidt, AFP/Getty Images

The Indian state of Rajasthan is a vibrant place. It’s home to the Pink City, Blue City, and Yellow City, and it also hosts a colorful cultural event each November called the Pushkar Camel Fair. Celebrated on a full moon day of the Hindu lunar calendar, it’s one of the largest fairs of its kind in the world. The annual gathering is a chance for traders to show off their camels and livestock, while also celebrating local culture and traditions. Both the people and camels sport brilliant attire, participate in a variety of competitions, and dance to lively music. (Yes, there’s video evidence of a dancing camel, but the word dance is used loosely.)

6. Birds of Chile Festival

Held each fall in Viña del Mar along Chile's Pacific coast, the Festival de Aves de Chile celebrates the beauty and diversity of the country's birds. Festival-goers have the chance to see Chile’s national bird—the wide-winged Andean condor, which happens to be one of the largest flying birds in the world—as well as other feathered friends in their natural environment. A series of excursions and talks featuring bird experts are organized each year.

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