[teddythetwig]

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...

[ItsMe000001]

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.