10 Most Gruesome Creatures in Nature to Spook You This Halloween

The supernatural reigns supreme on Halloween, but don’t sell Mother Nature short when it comes to the macabre. The natural world has some delightfully ghoulish creatures who don’t reserve their gruesome habits or wild looks to a single holiday.

I’ve written about many of these animals for National Geographic online, and sharing them makes me feel like a kid again. They are resourceful animals getting by in a tough world, just like us. It’s just that some of them might give Stephen King nightmares.

1. Coat of arms…and legs and heads.

Assassin bugs kill by spearing their victims with needle-like mouthparts, shooting then up with paralytics and digestive juices and turning them into a buggy protein shake which the assassin sucks up. But one, Acanthaspis petax, reserves a special postm-ortem ritual for the ants that are their favorite prey: they wear the corpses piled on their backs.

Why they do this is a question scientists from the University of Canterbury in New Zealand took on in 2007, as reported by National Geographic’s Ed Yong. They pitted assassin bugs against one of their predators, jumping spiders. (Here’s video of coated and non-coated assassins). The spiders were 10 times more likely to attack the naked assassin bugs—even dead ones—suggesting that the shape of the assassin is so effectively obscured by its corpse camo the spiders don’t recognize it as their usual prey and leave it alone. Another reason to wear ants: they come en masse and have nasty chemical defenses, so many insects don’t eat them.

Maybe one day they’ll turn up in beetle boots.

2. The peeing, puking, cleaning crew.

If you were to invent a Halloween bird you couldn’t do better than the turkey vulture, with its odd gait, bald head and ominous black wings. And yet vultures (there are 22 species) don’t kill anything; they are scavengers who eat the corpses of animals killed by other things, like disease or accident.

As the National Park Service points out, their dining habits help us out by ridding our fields and roads of rotting corpses that might expose us and other animals to disease. For a cleaning crew, however, vultures are hilariously messy. They urinate on their own legs, which, the University of Wisconsin’s Nature Navigator reports, helps them cool off and also sterilizes their legs and feet, helpful if you’re standing on rotting cadavers all day.

They also have a gross-tacular defense strategy: they vomit when threatened. The stink drives the interloper off and allows the vulture to make a quicker getaway.

Try it when someone starts to bore you at a Halloween party tonight.

3. Zombie snail.

The way some snails pulse and glow, you’d think they wanted to party all night long. Actually they’re the victims of some guests who won’t go away until they’re dead.

Snails of the genus Succinea pick up the parasite Leucochloridium paradoxum from eating delicious bird droppings on the forest floor. Once inside the snail, the parasite does two things: 1) it pushes its way up into the snail's thin tentacles, turning them into thick, white, pulsing beacons that look like vibrating maggots; and 2) it bends the will of the snail, making it crawl up into high branches where it becomes visible to birds which the parasite needs as its next host.

A bird mistake the snail’s tentacles for maggots and eat it, taking in the parasite which matures in the bird's gut. The bird poops out parasite eggs which another hapless snail eats and the parasite cycle continues on.

This NatGeo video of the whole grisly procedure is probably one of the best zombie flicks you’ll ever see. 

4. Voldemort would be proud.

The Harry Potter books were the birthplace of some dark, imaginary creatures, like the dementors, who drain human beings of all hope and happiness, effectively imprisoning them in their own misery.

As professor Michael Sharkey of the University of Kentucky pointed out in the Independent, “what is considered a fantasy among humans, the dementors of Harry Potter, is a reality in the world of insects.”

IFL Science reports that in a public vote, described in the journal PLoS One, a species of wasp in Thailand was named after J.K. Rowling’s ominous creature. The Ampulex Dementor wasp enslaves cockroaches by stinging the roach directly in the brain and filling it up with neurotoxins that cause the roach to submit to the wasp’s will. The docile roach allows itself to be led to the wasp’s nest where it is turned into a nursery: the wasp lays its eggs inside the roach and the wasp larvae eat its carcass until they grow up and leave.

Now that is a roach motel.

5. The world’s biggest spider.

Arachnophobes, come no further: a puppy-sized spider is running all over the Internet. It’s probably on your computer right now!

Not to worry: the massive tarantula, commonly called the goliath birdeater (though it only occasionally eats birds), inhabits the rain forests of South America, so it's unlikely to turn up in your shoe.

Still, it merits placement on the Halloween creatures list, and not just by virtue of its size, though the outsized one that made headlines recently, reported by an entomologist at Harvard, was about a foot long. In general they can get up to six ounces.

If their size wasn’t daunting enough, they’ve got some interesting weapons at their disposal. According to a video piece on National Geographic, they are covered with stinging bristles which they can release by rubbing their legs together. Their fangs can get up to an inch long—many locals like to roast the tarantulas and then use the fangs to clean their teeth. Says NatGeo, “It’s not often that your dinner comes with built-in toothpicks."

6. The real sea hag.

When UC Berkeley describes an animal as "Lovecraftian,” you know it’s gotta be, to quote Bob’s Burgers, gross-great. "Enter the hagfish. 

This primitive, eel-like creature has three hearts, but no eyes, jaw, or stomach. Its mouth has two tentacles around it and it feeds by attaching its “tongue-like projection,” equipment onto dead or dying fish on the sea floor, which it devours from the inside out, sometimes making the dead fish appear to be throbbing or moving. Susan Milius of Wired reports that they may also absorb nutrients through their gills and skin.

When a hagfish is alarmed (perhaps by a mirror because, well, look at it), it oozes a thick slime which occasionally fills up its nostrils, prompting a slime sneeze. In this video with a tankful of hagfish, you can see, at about 3:50 exactly how strong this excrescence is. Kind of like a paper towel commercial if the product were made of snot.

7. When two…or four…or six…become one.

If someone is going to compare your sex life to a movie you probably wouldn’t want the genre to be sci-fi.

Good thing you’re not an anglerfish, a bony fish that is literally light-headed: it has a luminous protrusion that comes out of the top of its head to lure the little fishies toward it. 

I’ve written about their bizarre sex livesbefore. The female angler is quite a big larger than the male and his way of mating is to bite into her side and hang on for dear life, or dear death because that’s what happens to him…kind of. As described on National Geographic, when the male bites into the female he begins to fuse with her, flesh melting into flesh, until he becomes nothing more than a sperm reserve for her to use when she’s ready to breed.

It’s called sexual parasitism. You can make your own “ex” joke right about here.

8. Parasite got your tongue?

As we’ve already seen, no undercover agent, party crasher, or human infiltrator of any kind has a thing on parasites for sneaky ways of getting themselves into the party.

The horse botfly, for example, lays its eggs on a horse’s coat, which the horse finds so annoying it will lick or bite them off. Equine Health UK describes how this stimulation makes those eggs hatch and the larval botflies burrow into the horse’s mouth—gums, tongue, cheeks—for about a month (causing no evident discomfort to the horse) until they travel to the stomach where they attach themselves to the stomach lining. Eventually they pass out through the manure into mature flies...which lay their eggs on a horse’s coat. And here we go again.

Botflies are a common horse pest according to EquiMed and can cause dental irritation ulcers and esophageal paralysis. And possibly cases of horses screaming, “Get it off me! Get it off me!” in their heads.

9. Parasite is your tongue.

While all these animals are undeniably Halloween winners, my personal favorite is a little isopod. Isopods are small creatures that live on land and sea; if you played with pill bugs when you were a kid you know what they are.

Those isopods were cute and funny. These isopods are hideous, body-snatching face hitchhikers. The marine isopod, Cymothoa exigua, is also known as the tongue biter, because when it's a little larval thing it swims into the gills of a fish and latches, with its grappling-hook legs, onto the fish’s tongue. It sucks the blood out of it and eventually eats the whole tongue away, but stays latched where it is, in the fish’s mouth, in effect becoming a replacement tongue and continuing to parasitize the fish. You can see them—and their cousins, the giant isopods, easily the size of a full grown cat—on this BBC video.

Talk about being somebody’s mouthpiece.

10. Parasites: they’re all in your head.

There is another type of botfly: the human botfly. As William Castle might have said, the squeamish among you should leave now!

Native to Central and South America, the female human botfly sticks her eggs to mosquitos (call it ovi-decoupage) which then bite humans; the warmth of our skin causes the botfly eggs to hatch and either fall into the mosquito bite, hair follicles or other cuts, writes Matt Simon of Wired.

And there it lives and grows, leaving a little hole in your skin so it can breathe, feeding on your exudate (a fluid rich in protein and cell debris produced when you get an inflammation, like a botfly, so at least it kind of brings its own lunch). Simon describes a girl who heard a crunching sound when she wasn’t eating: guess who came to dinner…right behind her ear?

A botfly will stick with you, causing pain and irritation—and a life episode you should not put on your Match.com profile—for about two months, unless you remove it first, which can be a tricky business.

HowStuffWorks.com offers this gruesome bon mot about botfly removal: “One method involves placing raw meat over the hole. When the maggot is unable to breathe, it burrows out into the meat.”

I’m going to recommend either a shrink or a drink to help you with your nightmares. Happy Halloween!