[terminado]

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.

[ItsMe000001]

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.

[neves]

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