The behaviour of flies depends largely on their species and environmental conditions. Some flies are active only during the day, while others are nocturnal. Some flies are attracted to light, while others avoid it. Some flies are solitary, while others form swarms or aggregations. Flies communicate with each other using various signals, such as sounds, pheromones, or body movements.

• House fly (Musca domestica) is the most widespread and familiar of all flies. It is attracted to a variety of organic materials, such as garbage, feces, and animal carcasses. It lays its eggs on these materials, and the larvae (maggots) feed on them until they pupate and emerge as adults. House flies can carry over 100 pathogens, including bacteria, viruses, and parasites, that can cause diseases such as typhoid, cholera, dysentery, and salmonella.
• Fruit fly (Drosophila spp.) is a small, yellowish fly that is often found near ripe or rotting fruits and vegetables. It can also breed in other moist organic matter, such as drains, garbage disposals, mop buckets, and beer bottles. Fruit flies are not only annoying, but also pose a threat to the quality and safety of food products. They can contaminate food with bacteria and fungi that can cause spoilage and infection.
• Blow fly (Calliphoridae) is a large, metallic-colored fly that is usually the first to arrive at a dead animal or human corpse. It lays its eggs on the carcass, and the larvae feed on the flesh until they are ready to pupate. Blow flies are important for forensic entomology, as they can help determine the time of death and other clues about a crime scene. However, they can also be a health hazard, as they can transmit diseases such as anthrax, tetanus, and leprosy.