Deer flies are small, biting insects belonging to the family Tabanidae. They are typically found in wooded or grassy areas, especially near water sources. Adult deer flies are known for their distinctive large eyes and yellow or brown bodies. They are most active during warm months and are attracted to movement and carbon dioxide emitted by animals and humans. These flies are notorious for their painful bites, which they use to feed on the blood of mammals, including deer and humans. Unlike some other flies, deer flies are persistent and can follow their hosts for long distances. Their bites can cause irritation and allergic reactions in some individuals.