Yellow flies are common, persistent insects, particularly in the southeastern United States, known for their painful bites. This article explains their biting behavior, how to identify them, and strategies for prevention and management.
The Biting Behavior of Yellow Flies
Yellow flies belong to the Tabanidae family, which also includes horse flies and deer flies. Only the female yellow flies bite, as they require a blood meal to produce eggs, a behavior similar to mosquitoes. Male yellow flies, in contrast, primarily feed on nectar and pollen.
Female yellow flies are “pool feeders,” meaning they do not pierce the skin with a needle-like mouthpart like a mosquito. Instead, they use knife-like mouthparts to cut the skin, creating a small wound from which they then feed on the pooled blood. This cutting action is why their bites are often immediately painful and can result in bleeding. Yellow flies are persistent once they locate a host.
Recognizing Yellow Flies and Their Bites
Adult yellow flies are medium-sized, typically 3/8 to 1/2 inch long, with robust, yellow or yellowish-brown bodies. Their forelegs are often black, while other pairs are yellow. A distinctive feature is their large, prominent eyes, often brilliant blue-green with two purple bands. Their wings are clear, sometimes with black veins or a brown patch near the tip.
A yellow fly bite causes immediate, sharp pain. A raised, red welt forms quickly, accompanied by intense itching and sometimes bleeding. Welts can be swollen and itchy, with symptoms lasting for several days.
Strategies for Preventing Yellow Fly Bites
Wearing protective clothing reduces yellow fly bites. Light-colored, long-sleeved shirts and long pants minimize exposed skin, as yellow flies are attracted to dark and contrasting colors. They are also attracted to vibrant blue.
Insect repellents with DEET, picaridin, or oil of lemon eucalyptus offer protection on exposed skin. DEET is considered most effective. Avoiding peak activity times, during daylight hours, especially morning and late afternoon, also helps. Minimizing time in known yellow fly habitats, like shaded, humid areas near forests and water bodies, is a practical measure.
Managing Yellow Fly Bites
If bitten, clean the area thoroughly with soap and water to reduce infection risk. To alleviate pain, swelling, and itching, apply a cold compress or ice pack for 10 to 15 minutes. Over-the-counter topical anti-itch creams, such as hydrocortisone or calamine lotion, reduce inflammation and itching.
Oral antihistamines can be taken to relieve itching and allergic responses. Avoid scratching the bite, as this can break the skin and increase secondary bacterial infection risk. Seek medical attention if symptoms worsen, if there are signs of infection (increased redness, warmth, pus), or if you experience severe allergic reaction symptoms (difficulty breathing, facial or throat swelling, dizziness, rapid heartbeat).