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What's the worst bug on the planet?

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You might vote for the horsefly[br]or perhaps the wasp,

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but for many people,

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the worst offender is by far the mosquito.

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The buzzing, the biting,

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the itching,

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the mosquito is one of the most commonly[br]detested pests in the world.

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In Alaska, swarms[br]of mosquitos can get so thick

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that they actually asphyxiate caribou.

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And mosquito-borne diseases[br]kill millions of people every year.

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The scourge[br]that is the mosquito isn't new.

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Mosquitoes have been around[br]for over a hundred million years

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and over that time have coevolved[br]with all sorts of species,

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including our own.

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There are actually thousands[br]of species of mosquitos in the world,

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but they all share one insidious quality:

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they suck blood,

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and they're really, really[br]good at sucking blood.

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Here's how they do it.

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After landing, a mosquito will slather

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some saliva onto the victim's skin,[br]which works like an antiseptic,

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numbing the spot so we don't[br]notice their attack.

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This is what causes the itchy,[br]red bumps, by the way.

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Then the bug will use[br]its serrated mandibles

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to carve a little hole in your skin,

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allowing it to probe around[br]with its proboscis,

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searching for a blood vessel.

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When it hits one,[br]the lucky parasite can suck

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two to three times its weight in blood.

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Turns out we don't really[br]like that too much.

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In fact, humans hate mosquitos so much

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that we spend billions[br]of dollars worldwide

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to keep them away from us --

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from citronella candles

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to bug sprays to heavy-duty[br]agricultural pesticides.

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But it's not just[br]that mosquitos are annoying,

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they're also deadly.

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Mosquitos can transmit everything[br]from malaria to yellow fever

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to West Nile virus to dengue.

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Over a million people worldwide

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die every year[br]from mosquito-borne diseases,

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and that's just people.

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Horses, dogs, cats,

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they can all get diseases[br]from mosquitoes too.

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So, if these bugs are so dastardly,[br]why don't we just get rid of them?

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We are humans after all,

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and we're pretty good[br]at getting rid of species.

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Well, it's not quite so simple.

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Getting rid of the mosquito[br]removes a food source

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for lots of organisms,[br]like frogs and fish and birds.

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Without them,[br]plants would lose a pollinator.

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But some scientists say

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that mosquitos aren't[br]actually all that important.

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If we got rid of them, they argue,

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another species would simply[br]take their place

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and we'd probably have far[br]fewer deaths from malaria.

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The problem is that nobody[br]knows what would happen

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if we killed off all the mosquitos.

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Something better might take their spot

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or perhaps something even worse.

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The question is,[br]are we willing to take that risk?

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(Buzzing)