I see a lot of lists like these around the net, but for the most part I tend to disagree with a lot of them. Partly it's because a lot of them tend to rely on urban legends surrounding actual animals (candiru, camel spider, earwig, etc. are nowhere near anything like they tend to get described as), or I just end up finding the creature way too fascinating to be afraid of it (I fucking love komodo dragons.)
Do note though, that this isn't the 7 scariest creatures on earth, nor even the 7 scariest things on earth to me (It'd just be the word "spiders" over and over.) These are merely 7 horrifying things that, well, amaze me in terms of how creepy they are, like they never really get any less creepy the more I know about them. Hell, they may even get -creepier- the more I read up on them. These are the living equivalents to horror films that manage to remain scary even on the 10th viewing, after you've read up on all the behind the scenes stuff and watched it with commentary.
I am so amazed that, in all my time watching horror movies, I can't recall a single time ever seeing a lamprey used. Slugs, rabbits, an AI controlled stealth jet, sharks, baboons, ticks, spiders, and even Clint Howard, but never a lamprey.
Basically, imagine an eel that attaches to your skin via suction, cutting into you in a circular motion, and then sucking your insides out. That's a fucking lamprey. That sounds so much like something from a Roger Corman movie, but I never see it happen.
Beyond that, their appearance is so unsettling that photoshopping their "mouth" of sorts onto anything instantly makes that image nightmare fuel. Just so many teeth, and really, the more teeth something has the more visually horrifying it is.
There's just something so strange about how they work, I guess. I mean there are more horrifying ways to die in animal kingdom, but the lamprey's manner of killing just reminds me more of something in a 1980's low budget New Horizons kind of movie rather than something I can watch a documentary on.
#6: Spider Wasp
Speaking of creatures that seem more like horror movie monsters than anything you'd find in reality, let's think back to one of my favorite films, Alien. You've got the facehugger, which orally rapes John Hurt, let's go of him, and then sometime later a fucking xenomorph breaks out of his chest while he's minding his own business eating breakfast (not to be confused with an unrelated incident where John Hurt was minding his own business at a restraunt when a singing alien burst out of him and imitated a racist singing frog.) Obviously, nothing like that could ever exist in real life, right?
In comes the spider wasp, one of the inspirations for the chestburster.
Let's say you're a spider. You're just roaming around, being a horrible abomination that doesn't deserve to exist, when that wasp suddenly attacks you. You try to fend it off, but in the end the wasp paralyzes you, carries you up to its nest (as seen in the above photo), LAYS AN EGG INSIDE OF YOU, and then traps you within the nest. After awhile, the egg develops into a young spider wasp larvae which begins EATING YOU FROM THE INSIDE. It does this over several months, until eventually emerging from your hollowed out corpse. Seriously.
That's just fucking horrifying. I hate spiders with a passion, but holy fuck that's just... god damn. It never gets any less creepy to me.
#5: Brown Recluse
First off, I wanna go ahead and say, yes, I know the brown recluse isn't that deadly in terms of its venom. It's the necrosis that brown recluse spiders are known for. Although there's heavy debate as to how many of the claims are related to actual brown recluse bites and not bites from similar spiders, that does little to make the brown recluse not utterly horrifying. Why?
Unlike many other dangerous spiders, brown recluses can be found across a good chunk of America. Sure they aren't as common as the black widow, but the black widow... depends way more on urban legend and exaggeration than the brown recluse. I wish I'd known that a long time back. I was cleaning a small gargoyle statue I had on my porch, when a few small black widows came out from a hole in it and onto my hand. Cue me bashing my hand with said statue to take care of them. I idiotically injured my hand way more than they could have injured me.
The brown recluse is hard to exterminate, found across most of the US, and will fuck your shit up. It doesn't need to be lethal to be horrifying as fuck. I'm not going to upload pictures of any of the injuries people have allegedly sustained due to them, but feel free to hop on google images and check them out yourself. I just wouldn't recommend it to anyone in southern Appalachia, especially if you ever plan on being around lumber for a long period of time.
#4: Humboldt Squid
I know what you're thinking, "How could a squid rank higher than a brown recluse?" Because this squid is pure, concentrated evil. It reminds me less of any other squid and more of the stereotypical demonic shark seen in multitudes of horror films. We're talking about a squid that will rip apart one of its own kind purely out of suspicion in no time at all, a squid that will even rip humans apart in a frenzy.
Although many who have studied them write that the humboldt squid is "more curious than aggressive" and tends only to be aggressive when feeding, it does little to paint a more positive light on a type of squid that has basically been exterminating large chunks of aquatic life with the frenzy that the humboldt squid has.
Deadly, aggressive, intelligent, the humboldt squid is easily one of the most horrifying (but not -the- most), creatures beneath the sea.
I don't know if words alone can sum up how horrifying these are, so I wanna go ahead and warn the squeamish: Bot fly larvae images unsettle even me.
Imagine yourself in her place. Just... god damn. These things lay eggs under the skin of not just squirrels, rabbits, cats, dogs, etc. but often times even -humans-. You might not even notice it, as it feels very much like a mosquito bite. Can you imagine that?
You're sitting there, thinking you just feel a mosquito bite, and you're annoyed at that. Mosquito bites suck. Time passes, and you get -that- nasty surprise. Seriously, that terrifies me. There's just something horrifying about something that can, rather sneakily, lay eggs beneath your skin.
They even go for your eyes! Jesus fucking tap dancing Christ. If this was the seven most -unsettling- creatures, they'd be number one, but I'm going by more than just unsettling with this list. Still, nothing makes me shudder and twitch more than fucking botfly larvae.
#2: Irukandji Jellyfish
The Irukandji jellyfish is a meter-long, nearly invisible jellyfish found in Australia, so you might be wondering how the hell they're more terrifying than anything else on this list. If you're wondering that, you've obviously never heard of Irukandji Syndrome.
Get stung by one of these things? You won't necessarily die, but you'll want to. Immense pain that anesthesia can't assist with that covers your entire body, nausea, vomiting, sweating, hypertension, anxiety, tachycardia, pulmonary edemia, and a crippling, doomed feeling that causes many of its victims to beg to be put out of their misery. When even anesthetized victims have been reported to still be screaming in agony, despite not even seeming concious, you know you're dealing with one of the most fucking horrifying things ever.
So what could possibly beat that? Well...
#1: Portuguese Man o' War
This is, without a doubt, the strangest, most horrifying thing on earth to me. Because it doesn't seem like it's from earth. This thing is... this thing is something H.P. Lovecraft would look to for inspiration. Seriously, take a look at that thing.
First off, that isn't a jellyfish, despite how it looks. It's actually multiple organisms working as one. The 'tentacles', which again are living things, are extremely venomous which they normally use to consume large quantities of fish, but they're also responsible for over 10,000 attacks on humans each year. The severity of these attacks range from intense pain and red welts, to, in some cases, -death-. These things are more dangerous than fucking sharks, and yet most non-Australians have never even heard of them.
Beautiful, yet very alien looking, this horrifying thing fascinates me so much. I think that, if I had to list my favorite aquatic creature, it would be this. It's the closest we've come to anything Lovecraftian beneath the sea, and I shudder to think we'll find anything worse.