The Deer Fly is a common insect found in North America, particularly in wooded and wetland areas. These flies are known for their distinctive yellow and black markings and can be easily recognized by their large, bulging eyes. Adult deer flies are typically active during the warmer months, especially in late spring and summer. Deer flies are notorious for their painful bites, which they use to feed on the blood of mammals, including humans. They are most active during the day and are attracted to movement and carbon dioxide. While their bites can be irritating, they are not known to transmit diseases.