Watch out … you might not always see  these five tiny creatures coming for you,   but chances are you’ve got one lurking  nearby ready to suck your blood.

We show you how they do it and how  you can get rid of them.

Enjoy!

This is the deadliest animal in the world.

Mosquitoes kill hundreds of thousands of people each year … the most vulnerable  people: children, pregnant women.

No other bite kills more humans … or makes more of us sick.

So what makes a mosquito’s bite so effective?

For starters, they’re motivated.

Only females bite us.

They need blood to make eggs ... and a pool of water for their babies to hatch in.

Even a piece of trash can hold enough.

At first glance, it looks simple -- this mosquito digging her proboscis into us.

But the tools she’s using here are sophisticated.

First, a protective sheath  retracts – see it bending back?

If you look at a mosquito’s head under a microscope, you can see what that sheath protects.

And inside there are six needles!

Two of them have tiny teeth.

She uses those to saw through the skin.

They’re so sharp you can barely feel her pushing.

These other two needles hold the  tissues apart while she works.

From under the skin, you can see her  probing, looking for a blood vessel.

Receptors on the tip of one of her other needles pick up on chemicals that our blood vessels exude naturally and guide her to it.

Then she uses this same needle like a straw.

As her gut fills up, she separates water from the blood and squeezes it out.

See that drop?

That frees up space to stuff herself  with more nutritious red blood cells.

With another needle, she spits chemicals into us.

They get our blood flowing more easily and give us itchy welts afterwards.

And sometimes, before she pries herself away,   she leaves a parting gift in her saliva, a virus or a parasite that can sicken or kill us.

There’s nothing in it for her.

The viruses  and parasites are just hitching a ride.

But this is what makes mortal  enemies out of us and mosquitoes.

They take our blood.

Sometimes we take theirs.

But often, not soon enough.

On to our next miniature vampire.

Let’s see how ticks dig into you with a mouth full of hooks, and the best way to pry them loose.

The hills are alive ... … with silent, waiting ticks.

Their bites can transmit bacteria that cause Lyme disease, and other things that can make us very sick.

Protected by these palps is a  menacing mouth ... ... covered in hooks.

First she has to find a host.

She can sense animals like us by  the carbon dioxide we give off.

She reaches out with her front legs.

Scientists call this questing.

It will use that claw to latch onto something … like your sleeve.

Now you see her ... ... now you don’t.

Once aboard, she searches out a  nice spot to bite into … for blood.

She lives three years, but in that  time she only eats three meals.

A tick needs enough blood to grow  from larva to nymph, nymph to adult, and then for females to lay their eggs.

Gross.

Let’s check out a nymph, a young tick.

It’s tiny, smaller than a freckle.

To grow into an adult, it needs  one blood meal, a big one.

The front of its body is all mouth.

It digs into us using two sets of  hooks.

The hooks wriggle into the skin.

They pull our flesh out of the way and push in this mouthpart: the hypostome.

Those hooks anchor the tick to us for  the long haul, like mini-harpoons.

While the speedy mosquito digs in, sucks  our blood and splits, all within seconds,   a tick nymph stays on for days.

Three  days, if we don’t find it before then.

Compounds in their saliva help blood  pool under the surface of our skin.

The nymph sips it through its  mouthparts, like drinking from a straw.

When a tick is full – and I mean completely full – it falls off wherever it may be.

Maybe onto your bed.

That’s if you don’t nab it first.

You might have heard that you should twist or burn the tick.

Not true.

Grab the tick close to your skin and just pull straight out.

That’s how you win the fight against those tenacious hooks.

If that didn't make your skin crawl,  this will definitely make your scalp itch.

It’s time to find out how lice turn  your hair into their personal jungle gym.

It can start as an itch.

Maybe a tickle on your scalp.

It’s head lice.

Tiny and tenacious.

Thanks to millions of years of evolution,  these suckers are not easy to get rid of.

You might end up in a salon,  but not the kind for haircuts.

Young lice are so small they’re almost  impossible to see with the naked eye.

Our scalp is their buffet.

They feed on our blood.

You  can see it inside this adult louse.

It’s that brownish stuff that’s moving.

The secret to their success?

Their claws – called tarsal claws –  and this little part, called a spine.

A pair on each of its six legs.

They’ve evolved to fit  perfectly around a human hair.

They make lice into speedy little  acrobats, using our hair like a tightrope.

They can’t jump or fly, but they get around.

Say two kids – one blond,  one brunette – touch heads.

The louse just scoots right over.

It’s been one long game of hopscotch,  from human head to human head.

And it has to be us.

Our head  lice can’t live on other animals.

In fact, other primates have their own species of lice, adapted to their unique hair.

Birds have lice that hide in their feathers.

Ooh.

Cozy.

And we all want them gone.

Common insecticides won’t  kill our head lice anymore.

They’ve become resistant to them.

Even their eggs have serious staying power, glued to individual strands of hair.

But lice do have a weakness.

They can’t survive away from our moist, warm scalp.

Head lice cannot even live on other hairy parts of our body.

So if you – or a professional – painstakingly comb them out, they’ll starve, and die within hours.

Okay, it’s not fun.

But it’s just a temporary encounter with a tiny hitchhiker that is biologically destined just for you.

These beauties are kissing bugs, but  you wouldn’t want to kiss one because  pretty quickly they swell into  a balloon full of your blood.

This kissing bug isn’t going to give you a loving peck when it sticks you with  that tucked-away proboscis.

It could actually make you  really sick, even kill you.

It makes its move at night, while you’re  sleeping.

It likes your warm body.

Kissing bugs get their name because  they often bite near the lips or eyes,   but they’ll dig in anywhere you’ve left uncovered.

A little anesthetic guarantees you won't  wake up while they feed on you for 10,  20, even 30 minutes.

Every kissing bug needs several huge  meals during the year or two it lives.

As it gulps, its exoskeleton  stretches like a balloon,   to fit up to 12 times its weight in blood.

This pliability is called plasticization.

How it started.

How it’s going.

All that hot liquid could stress an  insect’s body and stunt its growth.

So the kissing bug cools  it down – inside its head.

Your warm blood flows in.

The cool insect blood, called hemolymph,   absorbs the heat and releases it  through the top of the bug’s long head.

In this infrared video, you  can see the blood cool down   by more than 10 degrees Fahrenheit  before it reaches the bug’s abdomen.

So the bug is safe.

You,  on the other hand, are not.

It injects saliva as it sucks your blood.

Here’s a scientist squeezing some out.

The saliva has proteins that can give people a deadly allergic reaction called anaphylaxis.

And it gets much, much worse.

Okay.

This is super gross.

After eating – sometimes while it’s eating ... the bug poops.

And that poop – and urine ... might contain the parasite that causes Chagas disease.

If the bug’s victim rubs these feces and  urine into the bite wound or their eyes,   the parasite can infect them.

Years later, as many as one third of the people who got the parasite develop heart disease that can kill them, sometimes suddenly.

Pregnant women can even pass  the parasite onto their babies.

Few contract the parasite in the U.S.,  even though kissing bugs live here.

But in Latin America, millions  of people have become infected.

There, kissing bugs are known by many different names: chinche besucona … chinche … pito … vinchuca … barbeiro.

In rural areas, these kissing bug species live  in people’s homes, in the cracks of the walls.

And in animal coops.

Spraying has helped bring down infections.

But hundreds of thousands of people have  left their home countries for the U.S.,   not knowing the bug gave them the parasite.

A simple blood test can find it  and medications can often kill it.

In the American Southwest, the bugs live  in the nests of wild animals, like this pack rat den in Arizona, where biologists  Anita and Chuck Kristensen collect them.

Chuck Kristensen: Kissing bug, kissing bug!

Chuck Kristensen: Genuine kissing bug.

For the most part, they feed on the pack rats.

But in late spring and summer, the bugs sometimes  travel from these nests into someone’s home.

So sealing off your house, with  screens on your windows – and even vents –, is one way to keep  out these stealthy bloodsuckers.

When they feed on your blood,  tsetse flies can spread disease.

But their motherly instincts  are surprisingly familiar to us.

We mammals like to think we’re pretty special, right?

We don’t lay eggs.

We feed our babies milk.

Well, this very pregnant fly is about to prove us wrong.

Yep, this tsetse fly is in labor.

And that emerging bundle of joy is her larva.

While other insects can lay hundreds of eggs, she  grows one baby at a time inside her, just like us.

Congratulations!

Scientists think tsetse flies started growing   their young like this long ago  to guard them from parasites.

For that same reason, the larva doesn’t stick around.

It burrows into the dirt for protection.

It’s already gotten all the nutrition it needs from its mom’s milk.

That’s right, this fly makes milk.

Here’s a drop of it under the microscope.

It’s made up of protein and fat, a lot like breast milk.

The fly doesn’t exactly breastfeed, though.

Inside its mom, the larva got milk through these tubes ... which it drank with this pair  of strawlike mouthparts on its head.

A female tsetse fly needs a lot of fuel,   because over her 10-day pregnancy she  produces her own body weight in milk.

And that fuel comes from us.

Tsetses feed exclusively on blood ... from humans and other animals.

That’s bad news because where the flies  live in Africa they spread a debilitating   disease called sleeping sickness  in humans and nagana in livestock.

Tsetses make cattle so sick that  they can’t be raised efficiently   in a region of Africa the  size of the United States.

Geoff Attardo: All right.

Coming  back to the first trap we set.

Narrator: People are trying to control them  with things like baited traps.

Geoff Attardo: It looks like  it has a lot of tsetse flies.

Geoff Attardo: Holy cow!

That’s a lot of flies.

Man: Tsetse flies.

Narrator: They’re effective, but more defenses are needed.

That’s where Geoff Attardo, at the  University of California, Davis, hopes to help.

He’s trying to stop tsetse flies from making babies in the first place.

A female only mates once in her life, enough  to make the 10 or so babies she’ll have.

The male makes sure she doesn’t mate again   by delivering a substance that  makes her lose interest in sex.

Scientists are trying to figure out what it is.

If they could bottle it and spray it, female  tsetse flies may never get busy at all.

No more tsetse offspring to worry about.

After spending about a month  below ground in a hard shell,   the fly emerges as an adult and unfurls its wings.

Like us, tsetse flies ensure the next  generation by investing a lot in a few offspring, instead of investing very little in a lot of them.

They grow up so fast, don’t they?