I have a camp in Michigans Upper peninsula.  In spring, the mosquitoes, midges and black flies are in swarms, beyond verbal discription really. I have three of these; 2-15 watt units and a 40 watt model.  Running these between 8pm and 2am will clear 95% of these winged pests in a two acre area, within three days. The first night,  each will accumulate mosquitoes an inch thick . second night, about half that and downward to where I run the zappers every other or third night (on a timer) to maintain things.