Why do mosquitoes buzz and why do they bite you?

This is not a joke. These tiny insects are considered the most lethal animals in the world and contribute to more than 725,000 deaths a year. No other creature, not even us, is responsible for the loss of as many lives each year as mosquitoes.

Humans kill about 475,000 congeners each year. Snakes kill around 50,000 people, while dogs (mainly for rabies transmission) kill an additional 25,000. Some of the most feared animals, such as sharks and wolves, kill less than ten.

As for mosquitoes, I have a bad leg. If you hear the buzz of a mosquito in a place where I meet more people, the animal will choose me after a while as a priority objective of his lunch.

This leads me to ask myself some questions: why do mosquitoes ring in the ears? Have not you learned that your annoying hum is immediately followed by an attempt – usually unsuccessful – to break it?

And above all, why do they choose me and not my table companion, which seems to me more appetizing?

Notice to clbadmates

Mosquitoes do not buzz to warn their victims, but to attract the attention of other partners ready to mate. They can not stop it. The only thing that happens is that when they are buzzing around your head looking for a place to land and itch, their buzz sounds louder.

What you can be sure of is that even though both bades are very animated, the one around it comes from a woman. Males do not bite: they feed on nectar.

Both are necessary for the usual: to mate. Dr. Louis M. Roth, who devoted his youth to studying yellow fever transmitted by mosquitoes to the US Army, published in 1948 an article in which, among other curiosities concerning the mosquito Aedes aegypti, he realized that men did not know women every time they rested in silence.

Of course, as soon as the girls took flight and buzzed, the men chased them away frantically. The swarms of hundreds of men were calm until a female enters the swarm.

As soon as the female is detected by the sound of her flight, the males rush to intercept her guided by the sound. Roth, who had a lot of imagination and time, discovered that the inflamed men wanted to badociate with the tape recorder which emitted recordings with feminine buzzes and even with tuning forks that vibrated on the same frequency.

The role of sound

In 2017, two Russian researchers provided overwhelming evidence of the exceptional role that sound plays in the lives of mosquitoes, because of an organ discovered by a Baltimore physician, Dr. Christopher Johnston, there are more of 39, a century and a half.

A microscope in his hand, Johnston found that they had an organ in their antenna (known since then with the original small name of Johnston's organelle), which allowed them to recognize the buzz of other mosquitoes.

Johnston went to a better life without finding the mechanism with which the mosquitoes produced the noise. Among other things because he was not looking for it, convinced that it was good that the trick was to modify the vibrations produced by the changes of the wing tremor.

Half a century has pbaded before other scientists discover exactly what is causing the buzz. British entomologists Arthur E. Shipley and Edwin Wilson described in 1905 a shredded organ at the base of the wings that acts as a ratchet and produces sound when the wings move.

Victims in the honor

Let's see why and how female mosquitoes select their victims. The key lies in the invisible chemical landscape of the air around us.

Mosquitoes interpret this landscape through specialized behaviors and sensory organs able to read the subtle chemical traces that exhale our body.

Mosquitoes depend on carbon dioxide to find their guests. When we expel the air from our lungs, carbon dioxide does not immediately mix with the air. It remains temporarily in the scents that the mosquitoes follow like the rats at Piper Pied de Hamelin.

Mosquitoes perceive these scents and, like hunting dogs, pursue the trail by perceiving higher concentrations than those contained in normal ambient air. By using carbon dioxide, mosquitoes can locate targets up to 50 meters away.

Well, now, the mosquito that is going to sting me has located the group in which I am its auspicious victim. Things start to be personalized when the mosquito is about one meter away from the group of potential targets.

Nearby, mosquitoes consider a wide range of factors that vary from person to person, including skin temperature, water vapor, and clothing color.

Scientists believe that the most important variables on which mosquitoes are based when choosing a person are the chemical compounds produced by colonies of microbes living in our skin.

Bacteria convert the secretions of our sweat glands into volatile compounds that are captured by the olfactory system located in mosquito antennas. These chemical compounds are complex and include more than three hundred different compounds, which vary from person to person depending on their genetics and their environment.

Favorable diversity

According to an article published in the scientific journal Plos One, people with a greater diversity of microbes in the skin tend to have fewer mosquito bites than others with less microbial diversity in the epidermis.

The subtle differences in the composition of the chemical scents produced by different colonies of skin bacteria can explain the large differences in the amount of bites that a person receives.

So, since we can not control the microbiomes of our skin, we can not do anything except avoid getting dressed in black, because mosquitoes love this color.

This summer, I will wear yellow.

BBC