I had read that there are different types of flies which come out at certain times of the year, etc. Obviously I did NOT know our type flies OR I missed their 'season' because I only caught a few flies - when there were lots around when I began looking for a solution. Hoping to do better next summer. PS These are smelly & unsightly. Not something you want indoors or, in the least, near you. Maybe on a window sill, behind a curtain or blind.