Mosquito bites are nasty. On top being good conductors for various diseases such as malaria, yellow fever and dengue, they also leave you with an itch that lasts for hours, if not days. And even though human have invented body lotions and pesticides that theoretically should keep the flying blood suckers away, a recent study says that our efforts might be futile.
Biologists from the California Institute of Technology and the University of Washington have teamed up to investigate the issue. What they found was that not only are the dreadful insects rapidly gaining immunity to our body lotions and pesticides, they also have a trio of senses that they use to track down humans and distinguish them from other animals.
The most important one is their superior sense of smell, but sight and body heat come in handy too. Jeff Riffell, study co-author and biologist from the University of Washington, gave a statement saying that “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”.
Although previously conducted studies have touched upon the notion that mosquitoes might rely heavily on their sense of smell when hunting for food, which in turn may activate other senses, nothing was definitive. So Riffell and his team set put to investigate what those triggers might be, as well as which sensory pathways are the most important for finding a meal.
For their study, the researchers put some mosquitoes in an enclosed environment and used wind tunnels in order to track and record the behavior of the subjects. Riffell also explained why wind tunnels were so important to the experiment – they provide the researchers with good control over wind conditions, as well as the entire environment that the test subjects were flying around in.
This in turn enabled the experts to test various different cues and observe how the flying blood suckers responded to them.
The first thing they did was to test the mosquitoes’ sense of smell and try to understand how the insects use it. They released some carbon dioxide (CO2), a gas that humans exhale when they breathe, inside the wind tunnel through a small, black dot, and paid attention at the mosquitoes’ behavior. What they noticed was that the insects started being attracted to the black dot as soon as the gas started coming in.
Riffell informed that the odor stimulus seems to have activated the visual stuimulus in this particular case. The working theory is that the carbon dioxide (CO2) made mosquitoes believe that a warm blooded host could be found in the vicinity of the black dot. One possible explanation for this theory is that mosquitoes most likely don’t seek out a host until they smell it.
The next step was to insert heat (in the shape of water vapors) along with carbon dioxide (CO2) though the same black hole. The results showed that the mosquitoes were even more drawn to the black hole in this scenario.
The co-author pointed out that carbon dioxide (CO2) is the best sign that a warm-blooded animal is close by, and that mosquitoes can sense the gas from as much as 30 feet away. The insects then use vision as well as some of our other body odors in order to figure out if we’re a human, a dog, a cow or a deer.
The study was published earlier this week, on Thursday (July 16, 2015), in the journal Current Biology.
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