I had the top floor recently a fly invasion - the critters come probably like then through the roof when the temperature drops outside at night. The windowpanes were certainly full of flies (houseflies and mosquitoes smaller / Fruchfliegen). A few hundred, it must have been safe. After I glued 3 of poison strip with rubber gloves on the windows, were the next morning the floor and windowsills around the strip full of dead flies. After 2 days I had been resting. I did not count them but there have about 2 dozen houseflies and mosquitoes have been several hundred. Globol is very convincing!
