When mosquitoes bite people, how do they choose?

Mosquitoes like a man who has just exercised, exhales heavily, is a bit fat, smells like feet, and if he has just gone to the toilet and is wearing alfalfa perfume, all the females will give birth with his blood.

The words "quality human" correspond to mosquito favorites lactic acid, carbon dioxide, fatty acids, foot flavor, ammonia and 1-octene-3-ol.

These scents are combined to make a "human scent", also known as a mosquito trap, which attracts mosquitoes and kills them.

The number of articles corresponding to different odor molecules is different, which can be evaluated as hot molecules for research

It took 100 years of research to create a "human scent" to attract mosquitoes.

How to make the "human scent" that mosquitoes love.

1. The temperature:

As far back as 1910, people were studying how mosquitoes find people. But the idea that mosquitoes bite endotherms suggests that mosquitoes are sensitive to temperature.

To demonstrate this, the experiment was a bit crude: mosquitoes were placed in a net with hot water pipes outside, and the mosquitoes settled on the side of the warm net, indicating that mosquitoes were attracted to warm objects [1].

A mosquito that lands on one side of a net

But temperature alone is not enough.

If you think about it, 37 degrees in the summer, mosquitoes are most prevalent. Your body temperature blends in with the summer, 37-degree air is everywhere, and mosquitoes don't know where to bite.

It's not just the temperature that attracts mosquitoes.

2. Co2:

Then people focus on the smell.

In addition to temperature, humans, cows and pigs give off a smell that attracts mosquitoes.

In 1922, it was thought that carbon dioxide could attract mosquitoes [2]. They confirmed this hypothesis by successfully trapping mosquitoes in the wild with carbon dioxide.

There is only 0.035% CO2 in the atmosphere, while human exhaled air contains up to 4% CO2. Too many signals, mosquitoes don't suck you, even sorry for such obvious CO2 traces.

Mosquito traps have been developed to take advantage of the insects' fondness for CO2, attracting them with a "human perfume" that releases CO2 and other scents, then trapping them with a fan like an air purifier so they can't get out.

But if used clothes were placed in a house, mosquitoes still liked the smell of people even when no one was breathing out carbon dioxide. This suggests that human residual odor can also attract mosquitoes [3].

What else are mosquitoes attracted to?

3. "Human-flavor molecules" found in both humans and animals:

1) People who enjoy vigorous exercise are more likely to attract mosquitoes.

Strenuous exercise produces lactic acid. The lactic acid concentration in human samples is five times higher than that in other animals [4]. High levels of lactic acid mean blood is fresh, hot blood billowing in the veins, and every molecule of lactic acid beckons mosquitoes: "Come on, suck me!" [5]

2) Fat people are more attractive to mosquitoes.

Fat people release more fatty acids, while human skin emits short-chain (C2-C5) and medium-chain (C6-C11) fatty acid molecules, which are more attractive to mosquitoes [6].

3) The bathroom attracts mosquitoes.

Another human molecule that mosquitoes like is ammonia [7], and you'll often see mosquitoes in bathrooms.

4) Alfalfa, which cattle like to eat, attracts mosquitoes.

Mosquitoes are attracted not only to people, but also to cows. Alfalfa, which cows like to eat, contains a compound called 1-octene-3-ol, which also attracts mosquitoes [8], allowing them to recognize cows and suck their blood.

Ou Long has a perfume called pure qin alfalfa, I do not know how many true alfalfa there is, I wish the person who has used a lifetime of peace.

5) Feet attract mosquitoes.

And there are some weird studies. For example, among all parts of the body, the smell of feet is the most attractive to mosquitoes [9], so some people use used socks to make mosquito traps to effectively kill mosquitoes [10].

This kind of work, in which scientists rush to wear socks, store socks and go to the wild to catch mosquitoes and publish articles with a box of socks, lasted for many years. Finally, someone could not bear collecting socks and decided to study human odor in a more systematic way [11].

4. Systematic research on "human flavor molecules" to find unique "human flavor molecules" :

How do you systematically study human taste? The first thing is to collect a lot of body odor.

It's like the movie perfume.

In movies, men wrap attractive girls in oil, which absorbs fatty acids and other volatile molecules from the surface of the girl's skin. Finally, through the extraction and distillation of oil, the human odor molecules are preserved.

Modern technology is much more crude: a plastic film is wrapped around the person, and the gas is collected through a tube called a Tenax Sorbent tube, which is filled with porous polymers to which odor molecules can be adsorbed, and these molecules can be punched out by gas chromatography and mass spectrometry [12].

It turns out that humans have a lot of "human flavor molecules" as well as animals, but in different proportions. Some odor molecules are higher in humans, such as decanal and methylheptenone, which are more common in humans [12].

The molecules in these two odors are sebum metabolites. People with oily skin are more attractive to mosquitoes.

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5. Knowing what is "human", how do mosquitoes recognize "human"?

I talked about human taste, but what about mosquitoes?

This year, Nature published an article about the secret of mosquito smell in summer [12].

Here's how the experiment worked: when mosquitoes were exposed to low concentrations of natural human, rat, sheep, dog and plant scents, very few of their 60 olfactory spheres were activated. There is only one human smell specific olfactory ball.

Which human-smelling molecule activates the mosquito's "human-smelling ball"?

They then stimulated mosquitoes with individual human-smelling molecules and found that only decaldehyde activated the specific "human-smelling balls", while the other "human-smelling molecules" activated the others.

But mosquito bite, light decanal not, it is best to above several general "human flavor molecules", plus decanal this special "human flavor molecules" together, to both fast and good to attract mosquitoes.

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Conclusion:

A mosquito favorite "human scent" contains universal scents: CO2, lactic acid, fatty acids, ammonia, alfalfa; It also includes decanal, a odor molecule that is relatively specific to humans. Afraid of mosquitoes, you can find a love of sports, sebum secretion exuberant little fat together, he will help you feed all mosquitoes.