Why Do Some Black Flies Bite?

Biting flies are a type of fly that feeds on blood by using animals, including humans, as food sources. Many different species of biting flies exist, each one unique in its habitats and behaviors. Some biting flies can transfer certain diseases through their bites, which makes understanding the different types of biting flies that exist and the risks they pose essential for keeping you and your family protected and healthy.

Of the flies that bite, one of the most common in and around American households are black flies, also known as turkey gnats and buffalo gnats. Distinguished by a humped back, they can be yellow, brown, or gray in color.

Particularly prolific around creeks and rivers, black flies thrive in moist environments throughout the US, though they are most common in the northern regions, including the Arctic circle.

Both the female and male black flies feed on flower nectar, but the female black flies also bite animals, including humans, because they need the blood for their eggs to develop properly. In addition to humans, biting black flies may also bite:

• Dogs
• Cats
• Hogs
• Cows
• Sheep
• Birds
• Chickens
• Turkeys
• Horses

Not all female black flies bite, however. Those that do bite may feed on warm-blooded mammals and birds or cold-blooded animals, depending on their preferences.

Biting black flies are typically most active and aggressive during the middle of the day. When one bites, she injects saliva through the skin that may cause irritation, itching, swelling, and, in some cases, pain and a burning sensation. It can also transmit certain vector-borne diseases into the prey's body, including mansonellosis and onchocerciasis, or river blindness in humans. There is some speculation that biting black flies may even transmit encephalitis, though this has yet to be scientifically verified. Some people may also develop an allergic reaction to black fly bites that could become severe.

Biting black flies may travel up to 10 miles from where they breed to feed. While they prefer to bite around the head area of their prey, they may also burrow underneath clothing to feed. What primarily attracts biting black flies are:

• The CO2 you exhale when you breathe
• Sweat
• Perfume
• Dark-colored clothing

Insect repellent does more than keep the itching away, it helps protect you and your family from other potential hazards that come with pesky black flies. Proven Repellent is a picaridin bug repellent that offers 8 of protection from black flies with a single application.