The housefly is known to be an annoying pest around the house and pesters both animals and humans. One way that horseflies irritate other creatures is by giving them a painful bite. It is usually the female who bites other creatures and feed off of their blood while male horseflies usually feed on pollen and nectar from
flowers. Horseflies are usually observed in a hot climate. After the male and female horsefly mate, the eggs are laid on plants or stones near water. After the larvae are born, they live in water feeding on snails and other insect larvae.

Source: www.bartleby.com