Black flies, also called buffalo gnats, are pretty small even when fully-grown, reaching a maximum length of 1/8 inch (3.18 millimeter). These tiny flies have broad wings and a hump back. They prefer to reside in moist areas, such as creeks and rivers.

The black fly's main nourishment is blood. Although they generally don't transmit diseases to people in the United States, when present in large numbers, they can pose a serious threat to both humans and animals. Allergic reactions and blood loss from the bites have been known to cause death. Symptoms of black-fly bites include bleeding, itching and swelling [source: Illinois].

Here are some tips on how to prevent yourself from being bitten by black flies:

  • Avoid outdoor activities during the day, when black flies are most prevalent.
  • Cover up. Wear long-sleeve shirts and long pants when outside.
  • Use an insect repellent intended for biting flies.
  • Use fans or other devices to increase the air movement across patios, porches and other outdoor areas. Note: This method may not be 100 percent effective.
  • Use fly repellent candles or coils that contain citronella or other repellents that affects black flies.
  • Trim shrubbery and mow your lawn to reduce the black fly population. Black flies tend to rest on low-lying vegetation.
  • Use indoor space sprays if necessary.
  • Use crack and crevice treatments, if necessary.
  • Use outdoor barrier spays and treatments if necessary [source: Koehler, Oi]. //]]]]> ]]>