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.
More scary shit:
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.
A Human Bot Fly larvae, burrowing into your brain. Eating your thoughts.