This is a purple marten house. They're great guys to have around our new house. They eat mosquitoes all day long, but bats eat mosquitoes all night long. And poor bats, they're the most misunderstood maligned creatures on earth. People think they get stuck in their hair, they attack, they suck your blood. They do no such thing.
What they do do is eat a thousand mosquitoes an hour, all night long. And what you wanna do is attract them to your yard to cut down on the mosquitoes, and you do that by building them a bat house.
Building a bat house is really a pretty simple affair, but you will need a good set of plans. The U.S. Geological Survey, and a bat house is simply a bottomless box with slats inside where bats can roost during the day.
You'll need two 10 foot 1x12's, like this. Rough-cut cedar is the best. As you put it together, build crevices for them to fly in. This is the bottom of the box. They'll fly in here, climb up that roughened lumber, and roost here by day. At night they'll come out to eat insects all night long. Bats need it really warm. In fact, most of them brood at a temperature of 90 to 110 degrees, so you wanna seal out outside air. If you live in the north you may actually wanna paint your bat house black so that it absorbs the sun's rays. It needs to be about 15 feet in the air, and if it's possible to be within 500 feet of water, that would be a good thing, almost a sure fire way to attract bats to the backyard at your new house.