Feeding time!
It seems that when I'd rather they not, mosquitoes will gleefully oblige themselves and steal a belly full of blood anyway. Yet when I encourage them to "bite" for a photograph, they just hover around pretending they're not interested! I had to sit in the middle of a cloud of over twenty mosquitoes before this one finally decided to try for a meal. Interestingly, when I let a mosquito take as much blood as it wants, the area around the bite rarely itches or swells.