Somewhere there is an excellent punchline that would answer this question, but unfortunately I am not in possession of it.
The truth is that mosquitoes do not prefer blondes, brunettes, or any physical features of their host, for that matter.
What seems to be the most prevalent attraction for mosquitoes between one person and another is the composition of the perspiration on each person’s skin.
Sweat has certain chemical signatures that mosquitoes are very sensitive to, and a mosquito can detect and distinguish between over 20 different chemicals present in the composition of perspiration.
So, while gentlemen may indeed prefer blondes, mosquitoes remain indifferent.