Every morning there's a pile in the tray, which feels like proof it's working. Look closer. Moths, midges, beetles, the odd June bug. In one published study of suburban traps, 13,789 insects were killed and just 31 were biting flies: 0.22% (Frick & Tallamy). Consumer Reports agrees, quoting the American Mosquito Control Association — mostly moths, midges and beetles, very few if any mosquitoes. That's why the tray fills every night and your ankles look the same. So what is all that?