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Fri August 9, 2013
Mosquito Exclusive! Yes, They Bite, But Half The Time They Miss
Mosquitoes don't have a lot of time to do what they do. They land. They bite. They look for blood. Mosquito moms need that blood to feed their babies, which why only the females pounce. They know they're not welcome (Smack! Splat!) so they've got to be good at this; in, out, hitting their target most of the time. That's what I figured.
But I figured wrong. French scientists at the Louis Pasteur Institute in Paris were able to film mosquitoes biting for blood in fantastically extreme close up — and guess what?
They aren't that talented!
Here, for example, is a mosquito biting into the skin of an anesthetized mouse. What you will see is the mosquito's "mouth part," a complicated array of tubes, feeling their way in. Science writer Ed Yong says (on his blog, where I found these videos) the mouse's skin looks like a field of ice cubes. They palpitate ever so slightly. Each "cube," I guess, is a skin cell. But watch what happens ...
Nothing happens! Well, the mosquito's probe goes in. I thought it would be stiff like a needle, but no, once inside, the sharp, skin piercing parts slip off to the left and right — you can see them, extra thin and thread-like on either side — while the main sucky part slinks about, bending, twisting, looking for action. Try as it might, digging here, pushing there, its tip forking in two, it ends up with nothing — limp and defeated.
What you might call a "dry hole."
This footage comes from Valerie Choumet and her colleagues in Paris. They used a powerful lens and over and over, the mosquitoes missed. In this next try, the bullseye is sitting dead center in the frame. It's a small blood vessel, enticingly pink, but the probe hunts around, gets close — oh so close, but no ...
To my surprise, mosquitoes don't work quickly. They have to penetrate the skin, which involves grabbing onto some skin cells, bracing, and then plunging in (while staying loose enough to avoid my incoming slap). They can move that incredibly flexible mouth part, but since they have no eyes in there, they have to work by feel, and half the time, Choumet and company say, at least in these trials, the mosquitoes didn't find blood. That's not exactly a winning average. Plus, Ed says the process often takes a minute or two. That's a long time. So mosquitoes, it turns out, are not expert marksmen (or markswomen) — not at all. We all know they can bite, but the surprise is, as Ed says, "many suck at sucking."
Some of you, no doubt, want to see what it looks like when the mosquito gets to a vein and wins. Choumet saw that too, and I suppose, in all fairness I should share what she found, but because it made me queasy, because this is a blog and I don't have to be fair, and because I like giving mosquitoes bad press, I'm going to bury that video here.