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So I play soccer in evening at a nearby park. I noticed many times that after the game and even during it many mosquitoes hover over some of us. They sort of form a structure like a tornado. The more the one is sweaty, the more the mosquitoes. What can be the possible reason?

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  • $\begingroup$ Maybe they swarm all around our bodies, but we only notice them near our heads because that's where our eyes and ears are. $\endgroup$ – kmm Mar 22 '17 at 17:19
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    $\begingroup$ mosquitoes are attracted to CO2, lactic acid, and the bacteria that live in sweat (old sweat) physically active human emit all three. It makes sense that blood seeking parasite would be attracted to smells indicating blood containing organisms. $\endgroup$ – John Mar 23 '17 at 1:51
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In many mosquito species (and other diptera) males make swarm to attract the females. The vast majority of individuals in swarms are therefore males (but there are always a number of females in them as well).

These swarms are a type of lek mating which is also very common in midges (thanks to @arboviral for this info). Are you sure those you see are mosquitoes and not midges?

In order to produce these swarms, they typically hover a recognizable element in nature to swarm around, such as a small tree, a bush, a big stone, etc... On a soccer field, players are a distinct element to swarm over!

Of course, females are attracted to $CO_2$, warm bodies and odour of sweat but this is IMHO likely not an important factor causing the swarms you see. See @Kiny's answer on the subject.

References:

Also, why is this in the evening?

Mosquitoes typically start mating at the beginning of the evening and then forage during the night. However, this varies quite a bit from species to species. Aedes egypti for example, forage day and night while species of the genus Culex forage only for a few hours after the sun has set.

Such variation in the timing of mating behaviour can lead to (pre-zygotic) reproductive isolation between lineages. Potential reasons for being active at specific times and not others include temperature management, easier to parasite for females during the night (only females bite), timing with flowers (as both males and females feed on nectar). I would not be able to argue for why a specific species shifted its circadian rhythm in a specific way though.

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  • $\begingroup$ Also, why is this in the evening? Not in the morning or afternoon $\endgroup$ – AScientist Mar 23 '17 at 0:06
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    $\begingroup$ @ASuckerinMaths Please see edit $\endgroup$ – Remi.b Mar 23 '17 at 0:18
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    $\begingroup$ Gah - beaten to it! For reference this is called lek mating. You most commonly see it with midges, rather than mosquitoes, though. $\endgroup$ – arboviral Mar 24 '17 at 14:59
  • $\begingroup$ @arboviral Thank you! I edited the post to add the term lek mating. $\endgroup$ – Remi.b Mar 24 '17 at 15:04
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I found an interesting paper about the subject that could contribute to answering your question.

There are volatile substances that we produce that help attracts and repels mosquitoes such a geranylaceton, octanal, nonanal, and decanal (Logan et al.) The tests showed that those substances can both be used to attract and repel depending on their concentration with geranylaceton having a constant decrease in attraction.

Curious for more I have decided to look further into the subject and found another paper studying these components which states:

A blend formulated from the four aldehydes and combined with CO2-baited CDC trap without a light bulb doubled to tripled trap captures compared to control traps baited with CO2 alone. David P. et al.

Those four aldehydes referring to heptanal, octanal, nonanal, and decanal. which suggests that their attractive effect is stronger joined than separated.

Therefore, besides the "CO2, lactic acid, and the bacteria that live in sweat" stated by John, the reproductive behaviour stated by Remi.b there is also other volatile substances that make our attraction to mosquitoes stronger(or weaker).

References:

1. James G. Logan, Michael A. Birkett, Suzanne J. Clark, Stephen Powers, Nicola J. Seal, Lester J. Wadhams, A. Jennifer Mordue (Luntz), John A. Pickett. Identification of Human-Derived Volatile Chemicals that Interfere with Attraction of Aedes aegypti Mosquitoes.

2. Tchouassi DP1, Sang R, Sole CL, Bastos AD, Teal PE, Borgemeister C, Torto B. Common host-derived chemicals increase catches of disease-transmitting mosquitoes and can improve early warning systems for Rift Valley fever virus

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    $\begingroup$ Oh! Your right! thanks for pointing it out. Indeed after rereading it and without the acess to the paper my post makes little sense. I'll correct this right away. $\endgroup$ – Kiny Mar 23 '17 at 20:23
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    $\begingroup$ Again, welcome to Bio and +1 for a well-sourced answer $\endgroup$ – AliceD Mar 23 '17 at 21:59
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    $\begingroup$ Kiny, when you write to another user, make sure to add the '@', so to reach Mesentery write ' @Mesentery bladibla ' [I don't recommend adding the bladibla though ;-) $\endgroup$ – AliceD Mar 23 '17 at 22:14
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    $\begingroup$ @AliceD Oh! sorry! This is the first time I am partecipating in this sort of websites and as such I have no knowledge of how to properly go about doing things. $\endgroup$ – Kiny Mar 23 '17 at 22:16
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    $\begingroup$ @Kiny stop saying sorry! We're here to help $\endgroup$ – AliceD Mar 23 '17 at 22:17

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