General video · Level C1 - Part 1

How Mosquitoes Suck Your Blood

This is the deadliest animal in the world. Mosquitoes kill hundreds of thousands of people each year...

Level: C1 · 36 sentences

Transcript

  1. This is the deadliest animal in the world.
  2. Mosquitoes kill hundreds of thousands of people each year...
  3. the most vulnerable people: children, pregnant women...
  4. No other bite kills more humans...
  5. or makes more of us sick.
  6. So what makes a mosquito's bite so effective?
  7. For starters, they're motivated.
  8. Only females bite us.
  9. They need blood to make eggs...
  10. And a pool of water for their babies to hatch in.
  11. Even a piece of trash can hold enough.
  12. At first glance, it looks simple - this mosquito digging her proboscis into us.
  13. But the tools she's using here are sophisticated.
  14. First, a protective sheath retracts - see it bending back?
  15. If you look at a mosquito's head under a microscope, you can see what that sheath protects.
  16. And inside, there are six needles!
  17. Two of them have tiny teeth.
  18. She uses those to saw through the skin.
  19. They're so sharp you can barely feel her pushing.
  20. These other two needles hold the tissues apart while she works.
  21. From under the skin, you can see her probing, looking for a blood vessel.
  22. 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.
  23. Then she uses this same needle like a straw.
  24. As her gut fills up, she separates water from the blood and squeezes it out.
  25. See that drop?
  26. That frees up space to stuff herself with more nutritious red blood cells.
  27. With another needle, she spits chemicals into us.
  28. They get our blood flowing more easily, and give us itchy welts afterwards.
  29. And sometimes, before she pries herself away, she leaves a parting gift in her saliva:
  30. a virus or a parasite that can sicken or kill us.
  31. There's nothing in it for her.
  32. The viruses and parasites are just hitching a ride.
  33. But this is what makes mortal enemies out of us and mosquitoes.
  34. They take our blood.
  35. Sometimes we take theirs.
  36. But often, not soon enough.