This house was invaded by house flies, apparently intending to overwinter. We estimated this approximately 3000 square foot house had an average of at least 5 flies per square foot, giving a minimum total of 15,000 house flies.
The owner had passed away about two months prior (at a hospital, not here), and the house has been unoccupied. One of two roof-mounted swamp coolers was not sealed, and served as the point of entry. This house is on a large cattle ranch in the Chinese Camp area. The flies started coming in with the advent of cold weather in late October 2018. Ryan McQuoid of Foothill-Sierra Pest Control, Sonora California, did the service.
Service tech Ryan McQuoid and I did the video and treatment. October 30, 2018, Chinese Camp, Tuolumne County, California.