Why do midges/flies/mosquitos etc bite some people and not others?

Mosquitos can smell carbon dioxide. Our skin takes in oxegen and puts out co2. Like our lungs do. A mosquito can follow the co2 to its source. Mosquitos know that where there is co2, there is blood next to it. So basically the mosquitos want a blood meal and they know how to find a mammal who has plenty of it. As to which mammal a mosquito will choose to bite, they havn't figured that out, But If I was a mosquito I would certainly choose to bite you, you look delicious!