That reasoning never quite made sense to me because if that was a or the major reason, why do I have the signs of unwanted mosquito encounters mostly on or my feet and ankles?

If that theory indeed is true I think CO2 is just a rough guide to find the approximate location (within meters) of something alive with blood. I think once close other guidance systems might take over.

My above opinion isn't worth much, but the CO2 hypothesis seems pretty limited to me?

Mosquitos who feed on humans have developed behavior to bite around the feet because they are less likely to get smacked. https://www.npr.org/sections/goatsandsoda/2016/02/22/4655948...

Of course, that's an obvious conclusion - OPs point though was about CO2, which is unlikely to be what guides those vicious beasts to ones feet.

They detect CO2 and odors:

"Both Aedes aegypti and Anopheles gambiae mosquitoes — which transmitdengue and malaria respectively — were much less attracted to the scented beads after being exposed to the chemical. These results showed that the receptor responsible for detecting carbon dioxide also detects skin odorants."

https://www.nih.gov/news-events/nih-research-matters/how-mos...

And thermal features:

http://www.caltech.edu/news/mosquitoes-use-smell-see-their-h...

So, this might be a long shot, but I might hazard a guess that in hot, humid weather, with stagnant air, the dynamics of where exhaled exhaust goes, changes.

In the cold, dry air of winter your breath vents upward, but getting near sunny 90 degree weather, during summer time, it might descend and pool at the feet of gatherings of people at barbecues.

Carbon dioxide in ambient, matched temperature mixtures tends to be dense, and sinks toward the floor in many conditions (similarly true for carbon monoxide), but local conditions obviously vary, and odor travels differently than entire air masses. If mosquitos are already out, they probably travel along the odor gradient, toward the most concentrated area of scent.

You assume waaayyyy too much stability for a body of air. The air around you is moving constantly. Every bit of movement and every tiny heat source causes movement.

The problem is people don't see "air", but there are ways to visualize it (e.g. Schlieren photography). Or just watch smoke.

The mosquitos love my feet, even when I'm laid. Your theory does not match my anecdotal data.

CO2 is 44g/mol vs 29g/mol for air so perhaps it’s higher density causes more concentration close to your ankles.

Feet have more odour I guess. :)

Mosquitoes are generally attracted to Co2 but when it comes to differences between humans it's genetic. There are a few genes that influence it. See more in the veratasium [1] video below.

[1] https://veritasium.com/education/why-are-mosquitoes-attracte...

My husband is virtually immune to mosquitoes, while they find me irresistible. I'm smaller than he is and have a much lower base metabolism.

"I don't need to breath out no CO2. Just less than you."

I am 6'3" and 300 lbs. Mosquitoes pretty much ignore me.