Deer flies (genus Chrysops) are small to medium-sized biting insects in the horse fly family (Tabanidae) that are notorious for their aggressive behavior and painful, persistent bites. Unlike many other insects, they primarily hunt by sight and are attracted to movement, dark colors (especially blue), and carbon dioxide. [1, 2, 3, 4, 5]

Key Characteristics & Identification

• Appearance: They are roughly 0.25 to 0.33 inches long (smaller than horse flies) with yellowish-brown to black bodies.
• Wings: Their wings are distinctive, usually clear with prominent dark bands or patches.
• Eyes: They possess large, often brightly colored or iridescent eyes, frequently featuring gold, green, or purple patterns.
• Antennae: Their antennae are longer than their head, a key feature that distinguishes them from shorter-antennaed horse flies. [1, 2, 3, 4, 5, 6]

Biting Behavior

Only the female deer fly bites, as she requires the protein from blood to develop her eggs. Males feed solely on nectar and pollen. [1, 2, 3, 4]

The Bite: They use scissor-like mouthparts to slash the skin and then lap up the