Strange Japanese Giant Hornet

From: Japan, obviously.

Why you must fear it:
It's the size of your thumb and it can spray flesh-melting poison. We really wish we were making that up for, you know, dramatic effect because goddamn, what a terrible thing a three-inch acid-shooting hornet would be, you know? Oh, hey, did we mention it shoots it into your eyes? Or that the poison also has a pheromone cocktail in it that'll call every hornet in the hive to come over and sting you until you are no longer alive?

Think you can outrun it? It can fly 50 miles in a day. It'd be nice to say something reassuring at this point, like "Don't worry, they only live on top of really tall mountains where nobody wants to live," but no, they live all over the goddamned place, including outside Tokyo.

Forty people die like that every year, each of them horribly.

More scary:

Here's how the Japanese hornet treats other insects (and would presumably treat us, if we were small enough). An adult hornet will fly miles to find some squishy shit to feed to its children. Often times, it finds its food in, say, a hive inhabited by thousands of bees.

What to do? Well, Vespa japonica sprays the nest with some of the acid/pheromone and brings in reinforcements, usually consisting of 30 or so fellow hornets. They then descend upon the beehive like an unholy plague of hell-born death engines and proceed to make this world a scary goddamned place. This is maybe 30 wasps against 30,000 bees and the 30,000 bees do not stand a chance.

Behold the hornets systematically seize them with huge, wicked jaws and literally fucking cut them apart, one by one by one by fucking one. In three hours, there are piles of limbs and heads and just fucking bits of things that could possibly have been alive at one point, and the hornets have stormed the hive and flown away with all the bee's children. Who will then be eaten.

Strange fly: Bot Fly

From:
Most species found in Central and South America, some species found all over the world

Why you must fear it:
Oh boy. Ohhhhh boy. Okay, Bot flies.

There are dozens of varieties of Bot Fly, they're each highly adapted to target a specific animal, they have delightfully descriptive names like Horse Stomach Bot Fly, Sheep Nose Bot Fly and, hey, guess what. One of them is called Human Bot Fly.

They each have a different and elaborate reproductive cycle, all of which end with a fat, half-inch maggot embedded in living flesh. Feeding.

Horse Stomach Bots, for example, lay their eggs in grass. Horses eat the grass. And the eggs. Which hatch in the heat of the horse's mouth. Upon which they chew through the horse's tongue and burrow, through the horse, into its belly. Where they meet up and dig honeycombs into the horse's stomach. And get fat. When they're ready to be flies, they just let go and get pooped out of the system.

The Human Bot Fly lays its eggs on a horsefly or a mosquito, something that will attempt to land on a human. This carrier finds a human and lands on him or her. The eggs rub off onto the human, whose body heat hatches the eggs. The larvae drop onto the skin and burrow right the fuck in. Where they live. Under your skin. Eating.

Here's video of them removing one.

More scary:
Here is the best part. The larvae can grow anywhere in your body, it just depends on where the eggs wind up. Which could end up with you having a fat wormy thing in your tear duct. Or your brain. We know, because that's happened.