Several species of flies have adapted to live in human structures. When flies are found in human structures, they are always considered to be serious pests for major damages. Some kinds of flies are also a potential threat to human or animal health due to bacteria carrying insects. These flies may act as carriers of disease organisms present in their breeding and egg-laying sites and sitting on dirty places and can contaminate food for further diseases and serious illness. These disease organisms can cause food poisoning, diarrhea, dysentery or typhoid fever and many other fatal diseases that have a heavy process of cure.