Florida is home to at least six major types of biting flies, and the warm, wet climate means they’re active for much of the year. Whether you’re dealing with painful welts after a hike or tiny invisible attackers near the coast, knowing which flies are biting and when they’re most active can help you avoid them.
The Main Biting Flies in Florida
The most common biting flies across the state are no-see-ums (biting midges), yellow flies, horse flies, deer flies, stable flies, and black flies. Each one bites differently, shows up in different habitats, and peaks at different times of year. Mosquitoes technically qualify too, but most Floridians already know that battle well.
Yellow Flies
Yellow flies are widely considered the most aggressive biting fly in Florida. Only the females bite, but they do so vigorously, attacking all exposed skin with almost no warning because their flight is nearly silent. You typically won’t know one is nearby until you feel a sharp, sudden pain. The bites often produce large, itchy swellings that can last for days.
Yellow flies prefer shaded, forested areas near water. They’re active from March through November, with peak season running April through June. Late afternoon is their favorite feeding time, though cloudy days can trigger biting throughout the day. Unusually for flies in this family, yellow flies will follow you indoors. Dogs and other pets are also frequent targets, especially in shaded yards.
No-See-Ums (Biting Midges)
These tiny flies, less than 1/16 of an inch long, are the source of the maddening “invisible” bites many people experience near Florida’s coastline. Several species breed in coastal marshes, swamps, and mangrove areas, where they can reach staggering population densities. The University of Florida describes coastal no-see-ums as so numerous they can “drive even the most stout-hearted nature lovers indoors.”
Only the females bite, needing blood to develop their eggs. A single female can lay 50 to 110 eggs per batch, and the entire life cycle from egg to adult completes in just a few weeks under warm, moist conditions. That rapid turnover is why populations explode so quickly in Florida’s humid months. Bites cause a localized stinging or burning sensation with a red spot at the bite site. Most discomfort fades within minutes to hours, but people who are hypersensitive may itch for two to three days.
No-see-ums typically bite around dawn and dusk, but in cooler weather or along the coast, they’ll bite in broad daylight too.
Horse Flies and Deer Flies
These are the large, fast-flying biters you’ll encounter on trails, near lakes, and around livestock. Both are strong fliers, and only the females bite. Rather than piercing the skin like a mosquito, they use large mouthparts to slash the skin open and lap up blood. The result is a more painful bite that often bleeds afterward.
Horse flies are the bigger of the two, sometimes reaching an inch or more in length. Deer flies are smaller and often have patterned wings. Both are strictly daytime feeders and most active in hot summer and early fall weather.
Stable Flies
Stable flies look almost identical to common house flies, which makes them easy to underestimate. The giveaway is a sharp, needle-like mouthpart that projects forward from the head. Unlike most biting flies, both males and females feed on blood. They’re sometimes called “dog flies” because they commonly bite the legs and ears of dogs, though they’ll readily bite people too. Stable flies breed in decaying organic matter, so areas with livestock, compost, or seaweed accumulation along beaches tend to have the worst populations.
Black Flies
Black flies are small, dark, hump-backed insects that bite during daylight hours. They aren’t host-specific, meaning they’ll feed on whatever warm-blooded animal is available. In Florida, they’re less of a widespread nuisance than no-see-ums or yellow flies but can appear in large numbers near flowing water, where their larvae develop.
When Biting Fly Season Peaks
Florida’s warm climate means biting flies are present for a longer stretch than in most states, but activity isn’t constant year-round. Yellow flies have the most defined season: March through November, peaking April through June. Horse flies and deer flies are worst in hot summer months and early fall. No-see-ums breed continuously in warm, moist conditions, so coastal areas may deal with them nearly year-round, with the heaviest populations in the wetter months from late spring through early fall.
Time of day matters as much as time of year. Yellow flies are most aggressive in late afternoon. No-see-ums concentrate their biting around dawn and dusk. Horse flies and deer flies are exclusively daytime biters, often most active during the hottest part of the day. Stable flies bite throughout daylight hours.
Health Risks From Biting Flies
For most people, the primary health concern from biting flies in Florida is the bite itself: pain, swelling, itching, and the risk of secondary infection from scratching. Horse fly and yellow fly bites can produce especially large welts because of the way these flies tear the skin rather than puncture it. Some people develop outsized allergic reactions to bites from any of these species, with swelling that extends well beyond the bite site.
Biting midges and black flies are known disease vectors in other parts of the world, but in Florida the risk of fly-transmitted illness to humans is low compared to mosquito-borne diseases. The bigger concern for most residents is the sheer discomfort and the possibility of infection if bites aren’t kept clean.
Repellents That Work on Biting Flies
DEET remains the most broadly effective repellent against biting flies, working well on biting midges, black flies, and other species. Products with up to 30% DEET are considered safe for adults and provide the longest protection. Higher concentrations don’t repel better; they just last longer on the skin.
Picaridin-based repellents, even at lower concentrations, are labeled for mosquitoes, biting flies, and chiggers. Oil of lemon eucalyptus (the active ingredient is PMD) is a plant-derived option effective against black flies, gnats, no-see-ums, and mosquitoes, available in concentrations of 8 to 10%. IR3535, the active ingredient in some Avon products, is registered for biting midges, black flies, deer ticks, gnats, mosquitoes, no-see-ums, and sand flies.
For yellow flies specifically, repellents help but aren’t always enough. Because these flies are aggressive and attack silently, many Floridians also rely on physical barriers: long sleeves, light-colored clothing (dark colors attract them), and staying out of shaded, wooded areas during late afternoon in peak season. Some people hang sticky traps, painted black and coated with adhesive, in their yards to reduce yellow fly numbers around the home.
How To Treat a Biting Fly Bite
Wash the bite with soap and water as soon as you can. This is the single most important step for preventing infection, especially with the larger, messier bites from horse flies and yellow flies. Apply an ice pack wrapped in cloth for at least 20 minutes to reduce swelling. If the bite is on a limb, keeping it elevated also helps.
Over-the-counter antihistamines can calm itching, and standard anti-inflammatory painkillers help with pain and swelling. Resist the urge to scratch, since broken skin is the main pathway for infection. If a bite becomes increasingly red, warm, or swollen over the following days, or if you notice pus, that’s a sign of infection that needs medical attention.
Severe allergic reactions to fly bites are uncommon but possible. Symptoms like difficulty breathing, swelling of the face or throat, dizziness, or a rapid heartbeat after a bite require emergency care.