Question: I've noticed some flying insects invade my laundry room in the
last few weeks. The only way to describe them is that they look like
flies, but a bit smaller. They're easy to kill, but they keep comming.
When you kill them, they leave a mark on the wall as if they're made of
suit/dirt. What are these things, and how do you get them, and how do get
rid of them?
Thank you,
ANSWER Probably what you have are drain flies or moth flies. The two most common species are Psychoda alternata and P. cinerea. Both these species can occur in households or commercial establishments throughout the year, but they may be slightly more abundant in the summer.
These small, gray flies have 'fuzzy' wings, and are sometimes confused with moths. The adult flies don't move far from the site they are infesting, which is usually a drain. They are most often infesting the pipes leading away from floor drains, especially those drains that get a lot of organic material. This is usually the drain in the shower stall, tub, or in a washroom. They are sometimes found in a hospital or nursing facility.
The immature stages of drain flies live in the accumulated organic matter in the drain. The larvae feed on this slimy material, and are usually 'buried' in it. The fact that they are deep in the material makes them quite resistant to chemical control methods (regardless of how strong the drain and pipe cleaner you use).
The best (only!) control for these flies is to remove the breeding site, which is the organic material that collected in the drain. If these flies are present in the house there is almost certainly a slow or clogged drain. Find the drain and physically clean it out. All the liquid drain cleaner in the world will not solve the problem, you've got to physically remove the material causing the clog. Once the material is removed (along with the larvae) the problem is solved, except for the adult flies. They will live about 20 days, but since they will have no place to lay eggs, the problem will disappear when they die. .
