and laid an egg sac.

Luckily, roaches don't go out of their way to do this,

so it doesn't happen very often.

But there are a bunch of other unsavory bugs

that will lay eggs all over your body on purpose.

First up, the human botfly.

These insects, which are native to Central

and South America, glue their eggs to mosquitoes

and other blood-sucking insects.

When the mosquito bites you, the eggs hatch.

Then the larvae wriggle into your skin,

creating a painful pimple that leaks pus.

Or, as the baby botflies call it, lunch.

After five to 10 weeks, they escape.

Not long after that, they reach adulthood,

ready to mate, and start the cycle all over.

Another tropical parasite is Tunga penetrans,

more commonly known as the sand flea.

Females burrow into the bottom of your foot

and slurp your blood.

They start off smaller than a grain of sand

but grow to 2,000 times their size within a week

as they swell with your blood and up to 200 eggs.

Those eggs fall to the ground and hatch,

waiting for the next bare foot to pass by.

But some egg-laying parasites go more than just skin deep.

Tapeworms, for example, invade your intestines.

Adults can grow to be longer than a bowling lane

and block up your digestive system.

But it gets worse,

because they lay tens of thousands of eggs,

which can hatch and migrate,

spreading throughout your lungs,

muscles, and even your brain.

If that sounds gruesome, just wait till you hear

about the Loa loa worm.

It can be passed from human to human

by hitching a ride inside of deer flies.

When the flies bite you, the larvae enter through the wound.

After five months growing beneath your skin,

they reach adulthood and start to release

thousands of embryos a day.

Sometimes you can even see the worms

moving under your skin or across your eyeball.

But, hey, not every egg-laying invader is sinister.

Face mites, for example, are pretty innocuous.

They live on pretty much everyone's face,

and most people just never notice.

After all, they feed on facial oil, not flesh.

When it comes time to breed,

females just lay one egg inside of your pores.

Even better, researchers can now study your face mites

to track how your ancestors migrated across the planet,

because we usually pass them from parent to child,

so the mites stay in the family.

But face mites aren't the only helpful bug around.

Green bottle flies might be useful in medicine.

They lay their eggs inside of open wounds,

and then the maggots hatch and devour the damaged flesh.

That sounds brutal, but one day

we might be able to harness this process

to treat diabetic foot ulcers

and other slow-healing wounds.

Because when the maggots go to town,

they actually clean the area

and remove a lot of the dead tissue.

They even secrete proteins that reduce inflammation.

So maybe botflies, fleas, and tapeworms

could learn a thing or two

and at least make themselves useful

if they're going to move right in.