Ants have the capacity to become real-life zombies when a parasitic lancet liver fluke gets “behind the wheel” in their brains.

Africa’s great wildebeest migration and Mexico’s “living mountain” of fluttering butterfly wings are just two of nature’s many amazing and fun phenomena. But, especially appropriate for this time of year, nature holds some scary wonders, as well.

One of them is ants who become real-life zombies. A tiny, parasitic flatworm, known as the lancet liver fluke, can take over the brain of an ant, causing it to cling to blades of grass against its will. This mind-controlling worm can even press grass-grazing herbivores and snails into the scenario as other unwitting actors. Now, researchers are revealing more about the mind-bending powers of this ghastly parasite, a member—according to a paper published by the Australian Society for Parasitology—of the most abundant form of life on Earth.

On the human side of frightening spectacles is Vlad III, known as Vlad the Impaler, who was a 15th-century, military leader and prince of part of what is now known as Romania. He was so terrifying that he’s thought to have inspired the creation of author Bram Stoker’s literary vampire, Count Dracula. Now, a scientific examination of the letters of Vlad III is giving new insights into his nature (his environment and his health), suggesting that he probably had respiratory and skin conditions that could have caused him to cry literal tears of blood.

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Dressed in the Halloween colors of black and orange, monarch butterflies create a spectacle of nature when millions of them gather to overwinter in the Monarch Butterfly Biosphere Reserve, a UNESCO World Heritage site, in Michoacan, Mexico. ©Fernando Romo

The zombie brains of ants

A small flatworm can turn ants into zombies, say researchers from the University of Copenhagen’s Department of Plant and Environmental Sciences in a recent paper published in the Oxford University Press science journal Behavioral Ecology. And the parasitic worm’s ability to control the ant is even more cunning and sophisticated than previously believed.

Lancet liver flukes have a complicated, almost insane life cycle, which begins with the hijacking of an ant’s brain. The fluke then causes the unsuspecting ant to climb up and clamp its powerful jaws onto the top of a blade of grass, making it more likely to be eaten by grazers, such as cattle, deer or sheep. Impressively, the parasite can even get the ant to crawl back down the blade of grass when it gets too hot.

Getting the ants to go high up in the grass when cattle, deer or sheep are grazing in the cool morning and evening hours, and then down again to avoid the sun’s deadly rays, is quite smart. To learn how the flukes mastermind this strategy, the researchers tagged several hundred infected ants in the Bidstrup Forests near Roskilde, Denmark. They then observed the infected ants’ behavior in relation to humidity, light, temperature and time of day. It was clear that temperature affected ant behavior. When it was cool, the ants were more likely to be attached to the top of a blade of grass. When it got warmer, the ants relinquished the grass and crawled back down.


Most of Denmark was originally covered by forests, but after centuries of uncontrolled felling and clearance for agriculture, just 2 to 3% of the nation was covered by forests by 1800. Since adoption of the Danish Forest Act in 1805, forest clearance has been banned and tree-planting efforts were initiated.

Here’s the most fascinating part: several hundred parasites invade the ant’s body. But only one makes its way to the brain, where it can influence the ant’s behavior. The rest of the liver flukes conceal themselves in the ant’s abdomen, wrapped in a capsule which protects them from the host’s stomach acid. Animals infected with many liver flukes can suffer liver damage as the parasites move around the host’s liver and bile ducts. Meanwhile, the liver fluke that took control of the ant’s brain dies. You could say that it sacrifices itself for the others that are waiting for the ant to get them into their next host.

In summary, here are the players in the exceptional life cycle of the liver fluke:

1) The zombie ant: A liver fluke infects an ant’s brain, causing the ant to clamp onto a blade of grass so that its next host—a cow, deer, sheep or another grazer— eats it. Meanwhile, a large flock of flukes awaits transmission in the ant’s abdomen.


Liver flukes use ants to get into the intestines of grazers—such as cows—where they develop into adults and lay eggs, which are then excreted into the environment in the grazer’s feces.

2) The grazer: Once the grazer ingests an infected ant, it becomes infected with liver flukes, too. The liver fluke that took control of the ant’s brain dies in the host’s stomach acid. The capsule in the ant’s abdomen that protected the larger flock dissolves once in the host’s intestine. Here, the liver flukes find their way through the bile ducts into the host’s liver, where they suck blood and develop into adult flukes that begin to lay eggs, which are then excreted via the host animal’s feces.

3) The snail: Once the fluke eggs have been excreted, they lie on the ground waiting for a snail to crawl by and consume the feces. Within the snail, the eggs develop into larval flukes that reproduce asexually, multiplying into several thousand.

4) The slime ball: To exit the snail and move on to their next host, the larval flukes cause the snail to cough, thereby expelling them in a lump of mucus. Ants are attracted to the ball of mucus and consume it; and in doing so, ingest the fluke larvae. And, the cycle begins again.


Snails pick up the saga. They consume the grazer’s feces. Then, inside the snail, the eggs develop into larval flukes that reproduce asexually, multiplying into several thousand. They are expelled when the snail coughs.

The underestimated power of parasites

There are many other examples of parasites that alter animal behavior. They probably have a greater hand in the food chain than you think.

Historically, parasites have seldom been the subjects of focus, due in part to the fact that they are quite difficult to study. Nevertheless, the hidden world of parasites encompasses a significant part of biodiversity; and by changing a host’s behavior, they help determine who eats what in nature, making them important for us to understand. This new study sheds light on an extremely underrated group of creatures.

The tiny liver fluke is widespread in Denmark and other temperate regions worldwide. While researchers now know that temperature determines when the parasite will take over an ant’s brain, they hope that continuing investigations will reveal how and which cocktail of chemical substances the parasite uses to turn ants into zombies.

Public Domain (Wikimedia Commons), created by Candice Gaukel Andrews

The real Romanian prince, Vlad III, served as a model for author Bram Stoker’s fictional character, Count Dracula.

The surviving secrets of Vlad Draculea

And what would Halloween be without a mention of Dracula, the famous vampire? While a historical figure may have been the genesis for the fictional count, he is mostly a product of Bram Stoker’s and Hollywood filmmakers’ imaginations. There is, however, at least one natural, scientific reason for one of the many myths surrounding Count Dracula: although there is no real evidence to suggest that he drank blood, he likely did cry bloody tears.

The legendary, historical figure’s official title was Vlad III, Voivode (Prince) of Wallachia; and he lived in the southern region of what is now Romania in the mid-1400s. Although we suspect that Vlad III was not a real vampire, he was feared for his ruthlessness. Some estimates place his death toll at more than 80,000 people, many dying by impalement, earning him his nickname of Vlad the Impaler. He was also referred to as Vlad Draculea, which translates to “the son of the dragon.”

Though more than 500 years have passed since Vlad’s reign, some artifacts of his have survived, including several letters he penned at different points throughout his life. With technological advances, molecules and proteins present on these documents and other relics can now provide scientists with a unique understanding of the health of the infamous Vlad Draculea, as well as the environment he lived in.


Known in historical documents as Wallachia, southern Romania had a vulnerable position that substantially influenced its history. Bordered by the Carpathian Mountains in the north and the Danube River in the south, the region was located on the Ottoman border. Constant attacks and sieges took place for centuries, and most medieval fortifications were destroyed in the course of time. That’s why today you’ll see many more old churches here than defensive fortifications.

To uncover the letters’ secrets, researchers used a specialized plastic film called EVA, or ethylene-vinyl acetate, to extract any proteins or small molecules from the papers without damaging them. These extracts were then analyzed with mass spectrometry, allowing the scientists to characterize thousands of different peptides. Of these, the researchers focused on those with the most advanced deamidation, a form of protein degradation that occurs with age. The most degraded proteins were likely the oldest, and, therefore, the most likely to be from Vlad III, compared to newer, less-degraded proteins that could have originated from other people handling the letters more recently. A total of 16 proteins were of human origin, relating to breathing, blood and skin.

Reporting in the American Chemical Society’s publication Analytical Chemistry in August 2023, the researchers say that the data they acquired suggests that Vlad III could have suffered from respiratory issues and potentially a condition called hemolacria, which would have caused him to cry tears of blood—quite fitting for a spooky character.

Other proteins identified by the scientists indicate that he could also have been exposed to certain, plague-related bacteria or even pesky fruit flies.

Public Domain (Wikimedia Commons)

Bela Lugosi was a Hungarian–American actor, best remembered for portraying Count Dracula in the 1931 horror movie classic “Dracula.” Vampires (in the manner of Lugosi) remain one of the most popular costumes for Halloween.

The moody mental images of Halloween

Here’s what I’m picturing now, on this Halloween 2023: I see a little, cartoon worm at the oversized control panels of an ant’s brain. Like some mad scientist with a maniacal smile, he’s feverishly switching levers to the on and off positions.

Then, I conjure up a moody and monstrous royal from the far past, sitting at his dreary desk and penning angry letters, dampened occasionally by the red, viscous liquid that drips from his eyes like tears.

Now that I’ve set the stage, I’d like to wish you all a haunting Halloween,