How mosquitoes sniff out ‘tasty’ humans before biting

Washington, July 17 (IANS) Whatever bug repellents, scents or candles you may try to avoid mosquito bites, you just cannot avoid them as mosquitoes have evolved a triple threat of visual, olfactory and thermal cues to bite us, biologists have discovered.

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So, the minute they employ a razor-sharp sense of smell to tip them off that a warm-blooded meal is nearby, mosquitoes then use vision and other senses to hone in on the feast, revealed the team from University of Washington and the California Institute of Technology.

The bite occurs this way.

From 10 to 50 metres away, a mosquito smells a host’s carbon dioxide (CO2) plume.

As it flies closer – to within five to 15 metres – it begins to see the host.

Then, guided by visual cues that draw it even closer, the mosquito can sense the host’s body heat and decide to leave its mark. This occurs at a distance of less than a metre.

To find this out, the researchers released hungry, mated female mosquitoes into a wind tunnel in which different sensory cues could be independently controlled.

In one set of experiments, a high-concentration CO2 plume was injected into the tunnel, mimicking the signal created by the breath of a human.

In controlled experiments, the researchers also introduced a plume consisting of background air with a low concentration of CO2.

When a concentrated CO2 plume was present, the mosquitoes followed it within the tunnel as expected, whereas they showed no interest in a control plume consisting of background air.

Next, the team did the same CO2 plume experiment but this time they provided a dark object on the floor of the wind tunnel.

They found that in the presence of the CO2 plumes, the mosquitoes were attracted to the dark high-contrast object.

In the wind tunnel with no CO2 plume, the insects ignored the dark object entirely.

While it was no surprise to see the mosquitoes tracking a CO2 plume, “the new part that we found is that the CO2 plume increases the likelihood that they will fly toward an object”.

“That means that they smell the CO2, then they leave the plume, and several seconds later they continue flying toward this little object. So you could think of it as a type of memory or lasting effect,” the researchers explained in a paper that appeared in the journal Current Biology.

In an separate experiment, they found that mosquitoes showed a preference for the warm object.

But contrary to the mosquitoes’ visual attraction to objects, the preference for warmth was not dependent on the presence of CO2.

“A mosquito can see a visual feature from much further away so that happens first. Only when the mosquito gets closer does it detect an object’s thermal signature,” van Breugel said.

“Till date, very little was known about what a host looks like to the mosquito and how a mosquito decides where to land and begin to feed till now,” said biologist Jeff Riffell from University of Washington, co-author on the paper.

The work may help companies design better mosquito traps in the future.

3 Comments

  1. The mossies actually go for person who smells “sweet”… if some reports can be believed!

    And THAT reminds me of our Original Rampa – he is so sweet that a peda or gulab jamoon would taste like CHALK!

    Anyway – Rampa, do they bite you when you bang on your Dholu-mridu, and march in your Halloween costume around ‘Maddyson’ square, and go on an indefinite fast against BEEF, and/or talk to the blacks and the Irishmen that the should renounce Beef + all meat and instead – chomp on some spring onions and lettuce etc?

    So, do you apply Burnol? Or is it Vaseline? Or, maybe some mantra will ward off the darned Mozzy? Did you have some RSS pracharaka come take a look? Such a chweet boy, our Rampa – ODOMUS should help you if your local Bengali/Gujju/Mallu dime-a-shop fella should have it.

    And hey, you STILL haven’t told me WHO will address the ISIS mess. ARE you ACTUALLY waiting for BobbyANNA Jindal to open his hold-all and lay out his armaments, and ride piggyback on Madam Hilarious Clinton’s back and then annihilate them? Hope you have notified those expendables!

  2. “… blacks and the Irishmen…” writes Joker Praveena Pinto
    What a desperate but laughable attempt by saudi-returned Praveena to show off his rusted knowledge on doddanna’s cultural landscape that he probably learned from old black-and-white movies while aping his masters!! LOL

    Irishmen, uh? smiles…

    • …saudi-returned Praveena to show off his rusted knowledge on doddanna’s cultural landscape that he probably learned from old black-and-white movies while aping his masters!! LOL – Rampanna

      Aw shucks! Black & White movies and me?

      The last movie, B&W or otherwise, I watched was that eminently forgettable flick called ‘Bhagyada Baagilu’. I must have been 5 or 6 years old and I think it was good-old 1968.

      But then, I’m so sorry that I could not sit through the entire movie. You see, the last thing I remember was some fellow belting out this self-praise song called – ‘Naane Beejakumara’ while dancing round trees. I found it SO amusing that I rolled off my seat laughing. 🙂 I laughed so much that I developed cramps in my abdomen and had to be carried out of the theater by my Grandpa and administered some muscle relaxant jab by the nearest RMP (Registered Medical Practitioner). 🙁

      Thankfully, by the time I could sit straight, the show was over and I was spared more cramps! 🙂

      So WHAT B&W movies are you talking about ya Rampa? AND that too by my alleged “masters”? Please be a little more lucid!

      Btw, the other day.. wasn’t it YOU who said that Kimma Kay, Binga Crosby, Billa Mahera et al are a part of American culture? Gasp… gasp….. Please don’t give me more abdominal cramps! 🙂

      Go on ya Rampu. Your jokes are getting better. More plz. 🙂

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