This should not be called an insect killer. Maybe its a mosquito-ONLY killer. I don't know. I don't have many mosquitoes. What I do have are flies. I hung this machine about 2 inches over a fly ridden trash...I mean like around 50-100 flies and none of them got zapped. They would land on the outside and the rims, but I think the Flowtron made to much of a vibration and noise for them to want to land. I'm not a fly. I don't know why they won't land. This thing simply does not kill flies. A TOTAL AND UTTER WASTE OF MY HARD BORROWED MONEY.