Hugh,
It’s fall in Vermont, and that means cluster flies are back. Cluster flies enter buildings through the tiniest cracks imaginable; they work so hard getting in and then the next thing they do is beat themselves against the windows trying to get out. (This sort of parallels some people’s lives.) I normally have a company come out and spray the entire outside of the house to kill off the flies, but I didn’t get around to it early enough. Luckily cluster flies are more of a nuisance than a health issue. They do not lay their eggs in people food; they lay eggs in the ground, and the larvae feed on earth worms. In different situations, flies can be a major heath issue. To eliminate my cluster fly issue I recently purchased an industrial fly catcher from Paraclipse. I bought their Fly Patrol model. It’s just your basic UV light and fly paper trap with one neat idea incorporated into it– the fly paper is in a cartridge that gets rolled up very slowly, so fresh paper is exposed. When the unit signals that it’s at the end of the roll, just pull out the roll and put a new one on. It comes with a “decorative” enclosure that they show in their photos hanging on a wall. The unit is anything but decorative. The entire unit is ugly, and the sight of the flies on the paper is gross. However, the unit works wonders attracting and keeping the flies in it; I don’t have any fly issue inside my house now. I keep the unit outside the common areas of the house, so people don’t see it. The price for the complete unit is $156. Extra cartridges are about $10, and replacement UV bulbs are $13. (I don’t know how long the cartridges last yet.) If you have a flying insect problem, it might be worth a try. – C.L.