You got me beat there, nowhere near that big. Sometimes they make some pretty big blood spots when you swat them. Hard to compare size when you have not been every where.
Last week there were a lot of them. Last night (10:00PM) I was pumping water out of that low spot and went out to turn off the pump, did not hear any mosquitoes but lots of frogs. The water early in the day looked like it was boiling, must have been tadpoles. Not sure if the mosquitoes had already gone to bed or the frogs and tadpoles had done them in.
Next time I am out there at dusk I will find out.