Do flies bite?

The Illinois Department of Public Health states that deer flies, horse flies, stable flies, black flies, sand flies and biting midges do bite. According to Encyclopedia Britannica, houseflies are unable to bite because their mouths are designed to sponge or lap up food.

Biting flies locate their prey by sensing carbon dioxide and moisture in exhaled breath, warmth, perspiration, dark colors and movement. Once the flies locate their prey, they use their mouths to pierce the skin and inject saliva, which contains an anticoagulant, into the body to keep the blood flowing. The saliva sometimes causes a life-threatening allergic reaction in some individuals.