When we go trolling for walleye late at night in Northern Wisconsin, the white nav light on the boat draws mosquitos heavily. The mosquitos draw the bats, lots of them. Its a pretty cool experience to have a dozen or more bats diving and circling around the boat just at the edge of the light. You just catch glimpses of them.
It freaks my wife out, so she won't go walleye fishing with me and won't let the kids go either. Oh darn...
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I also have her convinced that the cigars we smoke keep the mosquitos at bay. Which is somewhat true, but we still use mosquito repellent. Don't rat me out! 
nothing better than walleye fishin in the dark

where do you do your fishing in WI? i usually go on the wolf river in the spring for the spawning run, mostly near Shiocton/New London area. in the summer i like night fishing on shawano lake, lake winnebago, or sometimes we'll make the drive to the petenwell flowage. many great spots here to nab a few "yellow pike"
back on topic.........when we sit out at the campfire at night, just as it gets dark, you can see bats zooming around left and right catching bugs. without bats, im sure we'd be eaten alive by the the wisconsin state bird: the mosquito