They can be a nasty problem in some areas. The small river which divides my farm, recedes into a series of pools during the summer and is an ideal breeding place for these pests. We have insect screens on every window, but the little beggars manage to get in sometimes and can make sleeping a bit of a chore..we don't like using bug spray as a rule, but every now and then have to resort to it. Same applies to the flies.