The air we exhale attracts mosquitoes, which is why the blood-sucking insects hover around our faces at night, disrupting our sleep with that infernal buzzing, research shows.
According to insect expert David Mifsud, for a mosquito, the smell of CO₂, or exhaled air, is a sign that there is a living creature close by – and fresh blood to feed on.
Dr Mifsud explained that CO₂ traps are used to attract mosquitoes and catch them for research.
“That explains why the mosquito hovers around your face and not your legs,” Dr Mifsud said.
Mosquitoes are also attracted to the scent of sweat and body odour, but it is not yet clear why some people are more prone to being bitten.
His theory is that it depends on a range of factors that make up the chemical scent emitted by individuals, which can vary depending on diet and possibly blood type, for example.
“They don’t really rely on sight but on chemicals,” he said, adding that, except for the Asian tiger mosquito, most are nocturnal.
New research, published in US journal Current Biology, unravelled a bit more of the mosquito mystery by suggesting that mosquitoes track down their host using a sequence of three linked cues: smell, then sight and, finally, heat.
The best tactic could be to create a distraction –like convincing a friend to wear a high-contrast shirt
Biologists recorded the movement of hungry female mosquitoes (only females feed on blood to nourish their eggs) inside a wind tunnel. The insects were instantly attracted to a plume of CO₂. After sniffing it, they homed in on a black spot. Finally, the mosquitoes were also drawn towards warmth.
Researchers found that if the insects were presented with a black spot in an otherwise empty wind tunnel, they left it alone.
In an interview with the BBC, author Floris van Breugel said that the unfortunate conclusion was that it was very difficult to escape from mosquitoes.
“If you were able to capture all the CO₂ that you were breathing out, then it’d be less likely that a mosquito would find you. But then if you were in a group of people, and somebody else wasn’t taking those precautions, then a mosquito would follow their CO₂ plume. And it may end up finding you before it finds your friend. So you’d want to be visually camouflaged as well,” he was quoted as saying.
The best tactic, he said, could be to create a distraction – like convincing a friend to wear a high-contrast shirt.