Flies belong to the class of Insecta and make up the order Diptera .
Drain flies are small, dark, fuzzy, moth-like insects. Drain Flies are called moth flies because of the long hairs on their wings, perhaps they look like small moths. These flies do not move far from the breeding site. They don't fly well at all and usually spend their time close to the site they are infesting. They are often found clinging to the walls of bathrooms, kitchens, or in the basement.