Black Flies

What Are They?

  • Black flies are also known as buffalo gnats and turkey gnats.
  • These are small flies that deliver a painful bite.
  • Scientists have placed them in the fly family called Simulidae.

What Do They Look Like?


Black flies are not very big insects. Depending on the species, they can be as small as 1/32″ in length. The large black flies are about ¼” long.


Scientists use the word “bulky” to describe the black fly’s appearance. The body is a little “humped” when it is viewed from the side.

Do They Bite?

Female black flies need blood to reproduce. They use their scissor-like mouthparts to make an incision into the skin and drink blood. These bites can be painful and leave itchy, swollen bumps.

Black flies bite exposed skin as well as underneath clothing. They seem to prefer areas where clothing fits snugly. The flies break the skin and then drink the blood that flows out. Feeding can last for several minutes.

Black fly bites usually hurt. The bite site often swells and itches. Red welts often develop where the fly bite happened. The area around the welt sometimes feels hot. People have reported that their hands or feet became very swollen after they were bitten by black flies.

Bite Symptoms

Bite victims often get headaches, fever, and nausea. There is sometimes swelling in the lymph nodes. Some people call this “black fly fever” The swelling usually goes down in a few days. The itching can last for weeks.

On Pets

Black fly bites on dogs are common as well. Scratching, whining, agitation, or unusual behavior may all suggest that a pet has a bite or is trying to ward off insect pests.

In the Home

Black flies only enter houses accidentally. They have not been known to bite when they come indoors. People who live in areas where black flies are common should make sure their home does not have any gaps or holes that the flies could use to get inside.

Experts recommend staying indoors during the black fly feeding times. If it is necessary to go out, they recommend using an insect repellant. The local pharmacy can recommend the repellants that work best in the particular area.

Life Cycle & Reproduction

life cycle
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Black flies live near streams. Male and female flies eat nectar for the energy they get from it. The females must get a blood meal in order to begin producing eggs that will hatch. The female flies deposit their eggs in the water or very close to the water. Eggs that are deposited during the summer will usually hatch in about a week.

The larvae develop in the water. They anchor themselves to plants or stones. They filter the water to get food. The larvae develop in about a month. They make a cocoon in the water where they change into adults. When the adults are ready, they float to the surface and emerge from the water.

Life Span
There can be as many as five generations in a year. Eggs that are deposited in the fall sometimes do not hatch until spring. Sometimes the eggs hatch and then the larvae spend the winter in the water.

Where Do They Live?

Black flies are especially bad in northern areas. They often occur near mountain streams. However, some species prefer slow-moving streams and even irrigation canals.

Black flies can occur in large swarms with many thousands of flies. In sunny areas they often feed in the morning and evening. In shady areas they tend to feed throughout the day.