“Red fly” is a label people stick on several different insects, from harmless swarmers to flies that bite or carry germs. Most of the red flies you’ll notice are no real threat, and some can’t bite at all. The real question is which one you’re looking at, because that decides whether you ignore it, guard your food, or cover up.
Which Red Fly Are You Looking At
- Fruit flies: tiny tan flies with bright red eyes that gather around ripe fruit and drains. They don’t bite but can carry germs onto food.
- Lovebugs: small black flies with a red-orange thorax, usually seen flying in joined pairs. They don’t bite, sting, or spread disease.1Gardening Solutions. Lovebugs
- Horseflies and deer flies: stout flies, often with colorful or reddish eyes. The females bite.
- Blowflies and flesh flies: metallic or gray flies, some with red eyes, that breed in garbage and carcasses.
- Screwworm flies: blue-green with an orange-red face. Their maggots feed on living flesh.2PubMed Central. The New World Screwworm in the United States: A Narrative Review Anchored to the 2025 Travel-Associated Human Case
Size is the quickest clue. Fruit flies are smaller than a grain of rice, while a horsefly can be thumb-sized. Then look at where you are: around the fruit bowl, on a car windshield, in a pasture, or by a trash can. Behavior helps too. Lovebugs drift along in joined pairs, while horseflies circle and land on skin.
Red eyes alone tell you very little, because fruit flies, some blowflies, and some biting flies all have them. Combine body size, body color, location, and whether the fly landed on you to bite.
A fly that lands on your skin, stays put, and then causes a sudden sharp pain is most likely a horsefly or deer fly. Fruit flies and blowflies can’t cut skin, so they don’t bite like this. A fly that keeps landing on your food or garbage lid is looking for something to eat or a place to lay eggs, not blood.
Harmless Red Flies Like Lovebugs
Lovebugs can’t bite or sting, and they aren’t poisonous.3Northwest Exterminating. lovebugs Archives They don’t spread disease or damage homes, and they’re safe around pets.4Fox Pest Control. What Are Love Bugs? Everything You Need to Know Their one real offense is to your car: their acidic body fluids can damage paint if dead bugs stay on too long, especially in hot weather.5Fox Pest Control. What Are Love Bugs? Everything You Need to Know During swarm season, wash the splatter off within a day or two.
Swarms show up mainly in late spring and late summer in warm southern regions. Spraying insecticide is rarely worth the effort because the swarms pass within weeks. A coat of wax makes dead bugs easier to wash off, and driving at dawn or dusk, when lovebugs are less active, means fewer splatters.
The pairs stay coupled after mating and fly tail to tail for a long time, which is why you see them in twos. Because they travel in dense clouds, they drift over warm, open areas like roads, where traffic turns them into splatter.
If a pet eats one, it may drool or gag at the taste. A vet visit is only needed if vomiting continues.
Horseflies and Deer Flies Bite Hard
The bite hurts because the fly uses saw-like mouthparts to cut the skin until small blood vessels break.6Natural History Museum. Are horsefly bites on the rise? An anticoagulant in its saliva then keeps the blood flowing while it feeds.7Natural History Museum. Are horsefly bites on the rise? Unlike a mosquito, it injects no numbing agent, so you feel the bite right away.8Natural History Museum. Are horsefly bites on the rise?
It usually feels like a sudden sharp burn or stab, and many people slap at the fly before they know what happened. Afterward a red, raised, itchy welt appears, sometimes with a small spot of blood where the skin was cut. Only the females bite, because they need a blood meal to produce eggs. The males feed on nectar and pollen.
A mosquito pierces the skin with a fine needle and often goes unnoticed. A horsefly slashes, so its bite hurts and bleeds more and tends to leave a larger swollen area that lasts longer.
The rarer risks are worth knowing. Scratching an itchy bite can break the skin and lead to a crusty, pus-filled skin infection.9News-Medical. Complications of insect bites Horseflies can pass on tularemia, a bacterial infection, and one Italian patient caught it from a horsefly bite.10PubMed Central. Case Report: Atypical Cutaneous Manifestations of Tularemia after Horsefly Bite In animals these flies spread diseases such as anthrax and equine infectious anemia, mostly by carrying germs on their mouthparts.11Journal of Medical Entomology. Review Article: Animal Disease Agents Transmitted by Horse Flies and Deer Flies (Diptera: Tabanidae)
Some people have a severe whole-body allergic reaction to the bites, and stings from bees or wasps should be ruled out as the real cause.12PubMed. Tabanidae insect (horsefly and deerfly) allergy in humans: A review of the literature If you’ve reacted badly before, ask a doctor about a written action plan and an adrenaline auto-injector.13PubMed. Tabanidae insect (horsefly and deerfly) allergy in humans: A review of the literature
For care at home, wash the bite with soap and water soon after it happens, since the skin has been cut and surface germs can get in. Hold a cold pack wrapped in a cloth against it for several minutes at a time to ease the swelling and pain. If the bite is on an arm or leg, raising the limb helps the swelling go down. An over-the-counter antihistamine or hydrocortisone cream calms the itch, and short nails or a covering over the bite keep scratching from breaking the skin.
Get emergency help for swelling of the face or throat, trouble breathing, or dizziness. Spreading redness, warmth, or pus in the days after a bite suggests infection. A fever with an ulcer or swollen glands needs checking for tularemia. A large local swelling alone is common and usually settles in a few days.
Red-Eyed Fruit Flies and Blowflies Spread Germs
Fruit flies can pick up E. coli, Salmonella, and Listeria from a contaminated food and carry them to clean surfaces.14PubMed. Fruit Flies as Potential Vectors of Foodborne Illness They can move germs from one ready-to-eat food to another, such as from a doughnut to lettuce.15PubMed. Fruit Flies as Potential Vectors of Foodborne Illness That’s easy for them, because they breed in dirty corners of the kitchen and rest on food-prep surfaces.16PubMed. Fruit Flies as Potential Vectors of Foodborne Illness A fly can keep carrying bacteria for up to 7 days.17PubMed Central. Mediterranean Fruit Fly as a Potential Vector of Bacterial Pathogens And rinsing fruit under tap water didn’t remove E. coli that flies had left on it.18PubMed Central. Mediterranean Fruit Fly as a Potential Vector of Bacterial Pathogens
Blowflies and houseflies carry bacteria from rotting material on their legs and wings.19PubMed Central. The microbiomes of blowflies and houseflies as bacterial transmission reservoirs Germs found on their bodies include Salmonella, Shigella, and dangerous strains of E. coli.20Tropical Biomedicine. The blow fly, Chrysomya megacephala, and the house fly, Musca domestica, as mechanical vectors of pathogenic bacteria in Northeast Thailand
Fruit flies are often brought in on produce from the store or garden, with eggs too small to see on the skin of ripe fruit. A tiny number can become a crowd in about a week, since they lay eggs on fermenting material and the young develop there quickly. That’s why they seem to appear from nowhere on a warm day.
To get rid of them, remove the source: overripe fruit, open trash, and damp drain gunk. A dish of cider vinegar with a drop of dish soap traps the adults. Keep ripe fruit in the fridge until the flies are gone.
If flies keep returning after you throw out the fruit, check the places where moist, sweet residue builds up: drains, garbage disposals, the bottom of the trash can, and recycling bins. A damp mop head or sponge left sitting can also host larvae. Tape a clear cup over a drain overnight; if flies collect under it, the drain is the source.
A brief landing on whole fruit you plan to peel or cook is low risk. Throw out fruit with bite damage or eggs, and keep cut fruit and leftovers covered. If flies have been around, wipe counters before you prepare food.
Screwworm Flies Are the Real Danger
Screwworm maggots burrow into living flesh and cause wounds that worsen quickly in people and animals.21PubMed Central. The New World Screwworm in the United States: A Narrative Review Anchored to the 2025 Travel-Associated Human Case The wound grows wider and deeper, often oozing pink fluid and sometimes giving off a distinctive smell.22Center for Food Security and Public Health. Screwworm Myiasis Maggots are usually visible in the wound by the third day.23Center for Food Security and Public Health. Screwworm Myiasis As many as 200 larvae can pack deep under a small opening in the skin.24Center for Food Security and Public Health. Screwworm Myiasis Early on, the wound may look like an ordinary sore, perhaps with pain, itching, or a feeling of movement under the skin.
Female screwworm flies lay their eggs at the edge of an open wound or in the moist tissue of a body opening, in warm-blooded animals and sometimes in people. The eggs hatch within about a day, and the larvae burrow into the living tissue to feed. Even a small scratch, a tick bite, or a sore can be enough of an entry point. Most blowflies lay eggs on dead animals and rotting food, while screwworm larvae feed on living flesh, which is what makes them so damaging.
Risk comes mainly from travel to Central or South America, the Caribbean, Africa, or Asia. Open wounds, sores, and sleeping outdoors raise the chance of eggs being laid. Outside affected areas, people very rarely see a screwworm fly. A travel-related human case occurred in the United States in 2025.25PubMed Central. The New World Screwworm in the United States: A Narrative Review Anchored to the 2025 Travel-Associated Human Case
After travel, a wound that keeps growing, smells, or seems to move needs prompt medical care. Tell the doctor where you traveled, and don’t try to dig maggots out of a deep wound yourself.
Treating Maggots in a Wound
Larvae need air to breathe, so covering the opening with petroleum jelly for up to 24 hours drives them to the surface.26DermNet. Cutaneous myiasis Once the larvae come up, they can be pulled out with tweezers.27DermNet. Cutaneous myiasis The aim is to remove the whole larva, because a piece left behind can cause inflammation or infection.
Antiparasitic drugs such as ivermectin are often used to kill the larvae.28Osmosis. Myiasis: What Is It, Causes, Signs and Symptoms, and More Severe cases need surgical removal, followed by antiseptic dressings and sometimes antibiotics.29Osmosis. Myiasis: What Is It, Causes, Signs and Symptoms, and More
Which treatment fits depends on where the larvae are, how many there are, and how deep the wound goes. A larva in the skin of a limb is handled differently from one near the eye, ear, mouth, or nose, where damage can be more serious. Only a clinician can judge this, so home removal of anything beyond a single shallow larva is not advised.
At the clinic, the doctor will examine the wound and may numb it before removing larvae. You may need several visits until every larva is gone, and keeping the wound clean afterward helps prevent infection.
Keeping Biting Flies Away
DEET and citriodiol, a repellent made from lemon eucalyptus oil, each cut deer fly bite attempts by about half.30PubMed. Protective efficacy of skin-applied arthropod repellents against Chrysops bites in a Loa loa hyperendemic region in Gabon: A placebo-controlled randomized clinical trial of DEET, icaridin, citriodiol, and IR3535 Icaridin and IR3535 gave no protection against deer fly bites.31PubMed. Protective efficacy of skin-applied arthropod repellents against Chrysops bites in a Loa loa hyperendemic region in Gabon: A placebo-controlled randomized clinical trial of DEET, icaridin, citriodiol, and IR3535 Repellents also didn’t stop flies landing on clothing.32PubMed. Protective efficacy of skin-applied arthropod repellents against Chrysops bites in a Loa loa hyperendemic region in Gabon: A placebo-controlled randomized clinical trial of DEET, icaridin, citriodiol, and IR3535 So choose DEET or lemon eucalyptus for horseflies, and wear light, covering clothes.
Apply repellent to exposed skin and also around the neck, ears, and hairline, where deer flies often go. Reapply after heavy sweating or swimming, since the protection fades.
Light-colored, loose, long-sleeved shirts and trousers make it harder for flies to reach skin and are less attractive than dark fabric. Thin, tight-fitting fabric can let a fly bite through, so looser clothing is better. Tucking trousers into socks closes off the gap at the ankles.
Horseflies are most active on hot, sunny, still days near water and woods. They are drawn to movement and dark shapes. A hat protects against deer flies, which often target the head, and sticky traps on a hat or dark ball can catch circling flies.
Repeated bites make animals restless, interrupt grazing, and can cause weight loss.33Cloud Peak Veterinary Services. Managing Horse Flies on Livestock: Prevention and Treatment DEET reduced horsefly numbers on horses by at least 71 to 80% for three to four hours after it was applied.34PubMed. Efficacy of the repellent N,N-diethyl-3-methyl-benzamide (DEET) against tabanid flies on horses evaluated in a field test in Switzerland On fly-heavy days, reapply repellent on animals every few hours.