Experts say watch out for invasive carnivorous flatworms

A photo of a hammerhead flatworm taken by Matt Bertone, an entomologist at the North Carolina State Extension. (Source: NCSE)

Authorities are urging those who live in the Knoxville area to beware of hammerheads when they step outside to enjoy the sunshine this summer. 

Not hammerhead sharks (which would have made this article a whole lot cooler, we admit). Rather, they’re asking us to keep a sharp eye out for a slightly smaller, slightly less lethal critter — the hammerhead flatworm.

“A long, slimy flatworm with a weird-looking head sounds like something from a science fiction movie, but it’s real and it has been documented in the Knoxville area,” says a statement posted on the Tennessee Valley Authority’s website.

Although this particular type of squirmy invertebrate lacks the fear factor of, say, a 1,300-pound man-eating fish with razor sharp teeth, authorities say you shouldn’t be fooled into thinking that hammerhead flatworms are harmless. 

The creatures are an invasive species, and they can do some pretty serious damage to regions where the native wildlife hasn’t adapted to them, experts say.

In fact, from the perspective of other animals in their weight class — for instance, the common earthworm and other soil-dwelling invertebrates —the snake-like hammerheads are bloodthirsty predators who devour their prey much like their oceanic namesakes do.

This is emphatically not a good thing, according to Jack Muncy, senior land conditions specialist for TVA.

“Our ecosystem in this region depends on earthworms, as strange as that may sound,” Muncy said in a recent post. “If earthworms are removed from the environment, plants and crops, even trees, are not able to get the nutrients they normally would. This is a similar effect we see with invasive species in the water, like zebra mussels—they upset the normal ecological balance.”

Scientists believe the hammerheads originated in Southeast Asia and were inadvertently brought to the United States in the soil of nursery plants. There have been several recent encounters with them in the small community of Norris, which lies just a few miles north of the Knoxville city limits.

Due to their size — usually between eight and 15 inches long — hammerhead flatworms are often mistaken for snakes unless their distinctive, half-moon shaped heads are clearly visible. 

Not only do they have the name of a shark and the appearance of a snake, experts say, but hammerhead flatworms also “secrete a toxic slime that makes them unattractive to predators.”

While this “toxic slime” normally only causes skin irritation in humans, no fewer than two types of hammerhead flatworm are “the first land invertebrates known to produce tetrodotoxin, the same potent toxin produced by pufferfish,” according to the North Carolina State Extension.

“This toxin is thought to help them overcome prey and also defend them and their eggs from predators. There is very little information about the toxin’s effects on humans, but it is likely minimal unless the worms are ingested in quantities. After handling these worms, it is advised to wash hands thoroughly,” says a study written by a trio of entomologists at the North Carolina agency.

A colorful example of a hammerhead flatworm, presumably captured in an odd moment of repose when it isn’t devouring the innards of its prey and planning how to overthrow primate civilization. (Courtesy TVA)

Oh — and if you chop off a piece of a hammerhead flatworm, they regenerate.


“To manage established populations, first and foremost it is recommended to not cut up the worms to destroy them, as cut fragments can generate a new worm from each section,” those same entomologists say (italics theirs).

Interestingly enough, experts do not recommend fleeing like a final girl in the latest Friday the 13th movie the instant you spot one of these poisonous/snake/shark/regenerating beasts. Nor do they recommend welcoming our new overlords with bowed heads, genuflection and child sacrifices.

No, they actually expect us to stand our ground and defend our East Tennessee soil against the slimy invaders.

The good news, apparently, is that household items like salt and rubbing alcohol have roughly the same impact on flatworms that garlic and holy water have on vampires. 

“If you see one, don’t touch it with your bare hands,” said Muncy. “And if you cut them, they can regenerate. The best way to get rid of one is to completely cover it with salt or rubbing alcohol, or use gloves to place it in a bag and freeze it.”


So, basically, get them drunk, pour salt on them, and then (careful not to let the toxic drippings touch your skin) freeze the little beasts until future generations can discover a way to overcome them.

Or you could, you know, just run. 

If you’d like to learn more about hammerhead flatworms before they overrun our frail and failing civilization, check out the above referenced article at

Or, take a look at the TVA post at

No, this isn’t the type of hammerhead that’s currently swimming its way through the topsoil under our toes. We’re apparently not that lucky, as hammerhead sharks lack both toxins and the ability to be cut in half and come back twice as angry.

J.J. Stambaugh can be reached at

Published on July 5, 2022.