Maybe they are different. I live in Asia. From what I heard there are many mosquito species, but the majority not blood sucking or at least not human blood sucking. Only few species carry disease, if I recall correctly.
To be fair, when I’m preoccupied, I also don’t feel them always. Or I feel them but my hands are busy, so I can’t slap them. I often have this at night, when I’m playing PC games and my feet get stung up. It’ll be like “ouch, my foot! Gotta slap that mosquito, but first I finish this in game. And then this.” Procrastinating until it’s too late.
I believe ankles are prime for them due to thin skin.