Mosquitoes
Not everyone is equally attractive to mosquitoes – who do they like the most?
Mosquitoes also like the mild summer evenings: however, they are picky. They bite certain people more than others. We show you which ones.
A small mosquito bite that, depending on your sensitivity, can be felt for a long time.
Build: Emanuele Biggs / Imago
Why do mosquitoes bite?
Not all of the at least 3,796 species of mosquitoes (Culicidae) bite humans. And even among those species that suck human blood, only the females bite. They pierce the skin using their mouthparts, a piercing-sucking proboscis, and absorb proteins and iron from the blood, which they need to produce eggs. Without blood, mosquitoes cannot reproduce. Apart from that, female mosquitoes, like males, feed on nectar and other sugary plant juices.
What attracts the mosquitoes?
Mosquitoes have a well-developed sense of smell. They can even smell carbon dioxide (CO₂) – and from a distance of more than 70 meters. They are therefore primarily attracted by the CO₂ in the air we breathe. Experiments have shown that the smell of CO2 activates the mosquitoes’ visual system – that is, they only look at us after they have smelled us. This is plausible, because while the sense of smell works over great distances, mosquitoes’ vision is focused on objects that are no more than about six meters away.
Does light play a role?
No. The mosquitoes do not react to it, unlike other insects such as moths. Electronic insect traps that use UV light are therefore of no use against mosquitoes, but rather harm other insects that are actually attracted to light.
Who do mosquitoes particularly like?
Since the carbon dioxide content in the air is crucial for whether mosquitoes can find us at all, people who exhale a lot of CO₂ are more attractive to mosquitoes. Athletes, tall or strong people, and pregnant women, who have a higher metabolism and therefore exhale a little more CO₂, are particularly affected.
Does our skin betray us?
After the mosquitoes have located us from a distance using their sense of smell and approached us, they also search for us with their eyes. Although they do not see very well compared to humans, they can perceive contrasts well. Dark or white clothing that stands out from the surroundings is therefore clearly visible to them. In addition, according to a study published in 2022, they can tell whether they are dealing with a human or an animal based on the color of our skin. This is independent of skin color, as all people have a spectrum of red and orange tones.
What is crucial?
When the mosquito comes within about one meter of us, the individual body odor is the deciding factor. This is caused by the decomposition of fatty acids that we secrete by bacteria on our skin. The fatty acids are similar, but the bacterial population is individually composed, and therefore different for different people. The odors caused by the decomposition of the fatty acids are therefore also different.
Finally, factors such as body heat and humidity also seem to play a role in whether a mosquito bites or not. If we are not warm, mosquitoes have little interest in us. On the other hand, if we are warm and also give off some water vapor – i.e. sweat – they are more likely to settle on us and feel us up.
What materials do mosquitoes like?
Among the chemicals contained in these fragrances, there are some that scientists have already identified as attractive to mosquitoes. For example, experiments conducted on human subjects in 2023 showed that carboxylic acids in human sweat seem to attract mosquitoes – at least the Anopheles mosquitoes studied. Carboxylic acids such as butyric acid or isovaleric acid are oily secretions that keep our skin moist and give off the unpleasant smell of sweat and cheesy feet when they are broken down.
Acetoin, which is produced by microbes on the skin and gives off a buttery smell, also seems to attract mosquitoes. And as early as 2009, an odor composition containing the aldehyde nonanal was identified as a mosquito attractant. But it is still not clear which mixtures of these substances make someone particularly attractive to mosquitoes. After all, there are around 100,000 components that make up a person’s individual scent.
How do mosquitoes perceive these substances?
The insects perceive these substances not only through their sense of smell, but also through taste receptors on their feet. Thanks to these, they find the best place to sting after landing on the skin.
Are our genes to blame?
How we smell also depends on our genetic makeup. In an experiment with twins in 2015, scientists proved that our genes actually have an effect on whether mosquitoes find us attractive. They examined 18 identical and 19 fraternal female twin pairs. Identical twins hardly differ genetically, while the genetic makeup of fraternal twins is as different as that of other siblings.
In fact, it was found that the identical twins attracted mosquitoes to a very similar extent, while the fraternal twins proved to be attractive to the insects to varying degrees. However, it remained unclear which genes were responsible for this.
