Phorid flies lay their eggs and feed on decaying food, rotting plants, manure, and decaying animal carcasses. They are particularly fond of the decaying materials that are found built up in the drains of sinks and bathtubs but they can also become problematic in homes and other buildings if there is a water leak under the foundation or behind a wall. These flies will flourish in those moist areas and enter into your house through any small cracks and crevices that they find.
Phorid flies are found living and feeding on decaying materials and feces which means that when they enter into your home they can contaminate food sources and food prep areas with serious diseases. Because these flies are so unsanitary, they can cause serious issues in hospitals (invading wounds) and restaurant facilities.