Drain Fly This is one of those small black flies that breed in sewage sludge that accumulates in various places such as the floor drain in your basement. They like to hang out on the walls of a basement shower stall or anywhere there is a neglected drain without a trap. Over the years, I was plagued by these flies at various times until a friend told me to pour some household bleach down the drain. Viola! They're gone for several weeks. Repeat as needed. I never knew what these things actually looked like until I photographed them. I was stunned to see their structure; the feathery antennae and furry appearance. Very strange, I thought, and then wondered if they were not moths? Nay, sayeth my buds at bugguide. They be moth flies. Ok. I'll continue to call them drain flies. Reference: bugguide.net