Depends..... Mine fly at night when there is full moon. Often see bees coming back an hour after dark. I use a yard light, after an old timer told me the bees use the light as a landmark to find the way back late. I would Timer it to a couple hours after dark , using the Off switch for the 3 days before and after full moon. Place a tarp under the zapper and stop if the dead bees get too thick.
GG
