The Flowtron BK-40D works great hanging from a tree thirty feet behind my house on a waterfront lot.  I plugged mine into a timer to turn on at sundown and run for three hours.  It attracts bugs away from the house (lights) and zaps them, so sitting on the back porch or going in and out at night is much more pleasant for us humans.  And, there are fewer spiders webs around the house and fewer bugs in them.