Yellow flies are serious biters that live in the Bahamas, in the United States from New Jersey to Texas, and from Mexico to Costa Rica. Experts recognize only one species, Diachlorus ferrugatus (Fabricius), as the true "yellow fly," also known as the "doctor fly" in Belize, according to University of Florida Institute of Food and Agricultural Sciences online. The fly, about 1 cm long, inflicts a painful bite.

Bite Location

Yellow flies bite on any area of the human body, however, they mostly attack the shoulder, neck and head areas. Often biting in groups of three or five in conjunction, the flies often seem a nuisance at first until the first painful bite is inflicted and then the bites become unbearable. Like the mosquito, only the female yellow flies bite. They bite more often in hot summer and early fall weather. The yellow fly attacks more aggressively in late afternoon and in humid areas, including creek, river, pond, forest or ocean inlet edges near tree shelters.

The Bite

Yellow flies, like mosquitoes, sense substances including carbon dioxide, perspiration, moisture in exhaled breath and warmth in humans as it chooses a suitable host. Once it finds a host, the fly inserts the piercing mouth part, lacerates the skin, then injects anticoagulant-containing saliva to keep the blood flowing. The bite can transmit diseases and the saliva can trigger life-threatening allergic reactions to sensitive individuals.

Bite Symptoms

A bite from a yellow fly is extremely painful and the bite area itches persistently. The bite area experiences swelling. The amount of swelling depends upon the individual's reaction to the bite. The area will be a raised swollen red area, hard and hot to the touch. Scratching may help alleviate itching for a moment, but it will only inflame the pain and inevitably increase the itchin. Yellow fly bites are distinguishable from other insect bites because of their increased swelling and large size.

Bite Relief

For relief of a yellow fly bite, mix 1 tsp. baking soda, 1/3 cup ammonia, 1/3 tsp. meat tenderizer and one crushed aspirin in a closed, labeled container and keep it cool in the refrigerator. Dab the mixture onto the skin gently with a cotton ball or a cotton swab.