If you've ever weeded the garden or walked a trail in Bridgewater on a warm late-spring day and come home with itchy, bleeding bites along your hairline, black flies are a likely suspect. They're tiny, they swarm around your face and they bite before you notice them. The good news is that they don't move into your home, and a few simple habits make a big difference outdoors. Below, we'll explain what black flies are, where they come from, how to tell them apart from other biting insects and what you can do about them. If flies are a bigger problem around your property, our fly control team can take a look.
What Black Flies Are
Black flies are small, dark flies with a distinctly humped back. Many people call them buffalo gnats for that reason. They're smaller than a house fly, with short antennae and clear wings, and they fly in loose, persistent swarms around people and animals.
Only the females bite. They need a blood meal to produce eggs. Males feed on nectar and plant juices and never bother you. Instead of piercing the skin with a thin needle the way a mosquito does, a female black fly cuts the skin and feeds on the small pool of blood that forms. That's why black fly bites often bleed a little.
Why They Show Up
Black flies are tied to running water. The females lay their eggs in or near flowing streams and rivers. The larvae attach themselves to rocks and plants in the current and filter food from the moving water. Once they mature, adults emerge and fly off in search of a meal.
That has two practical effects for homeowners:
- They don't breed in your yard's standing water. Bird baths, buckets and clogged gutters breed mosquitoes, not black flies.
- They can travel to you. Adults fly away from the water where they developed, so you can get bitten even if there's no stream on your property.
Black flies are daytime biters. They're most noticeable from late spring into early summer, especially on calm, humid days, and they tend to ease off in the heat of midsummer.
How To Tell Black Flies From Other Biters
Several small insects bite outdoors, and it helps to know which one you're dealing with.
| Black Fly | Mosquito | Biting Midge | |
|---|---|---|---|
| Look | Dark, stocky, humpbacked | Slender, long legs | Barely visible |
| When it bites | Daytime | Often dawn, dusk and night | Dawn and dusk |
| Where it breeds | Running water | Standing water | Wet soil and mud |
| Favorite target | Head, ears, neck, hairline | Any exposed skin | Any exposed skin |
If your bites come at dusk and you never see the culprit, read our guide on how to stop biting midges.
Are Black Fly Bites Harmful?
For most people, black fly bites are a nuisance, not a danger. They can be painful at first and then itch and swell for several days. Bites often cluster where the flies crawl under the edge of a hat, behind the ears or around the collar.
Some people react more strongly, with larger swelling, headache or feeling unwell after many bites. If you have a strong reaction, a bite that looks infected or symptoms that worry you, see a doctor. Try not to scratch, since broken skin can become infected.
How To Keep Black Flies Off You
Because black flies breed in moving water, there's no bucket to dump or container to scrub. Treating streams isn't something a homeowner can or should do. Your best defense is protecting yourself.
- Use an EPA-registered repellent. Apply it to exposed skin, including your neck, ears and hairline, and follow the label.
- Dress light and covered. Black flies are drawn to dark colors. Light-colored long sleeves and long pants help, and tucking pants into socks keeps them from crawling up.
- Close up the gaps. Button collars and cuffs. A head net is worth it for long outdoor chores during peak season.
- Time your yard work. On calm, humid days, black flies are at their worst. A breezy day or a later afternoon can be much more comfortable.
- Keep air moving. A fan on the patio or deck makes it harder for small flies to land.
- Keep screens in good repair. Black flies rarely bite indoors, but a torn screen still lets stray flies in.
When To Call A Professional
Black flies themselves are hard to control at the property level, since their breeding sites are in moving water. What a professional can do is sort out what's really biting you. Many homeowners who think they have black flies actually have mosquitoes, midges or other flies breeding much closer to home, and those can be treated. EcoFusion uses Integrated Pest Management and EPA-registered eco-safe products, and our outdoor pest control service targets breeding spots around your yard.
Black flies are a seasonal annoyance tied to running water, not a sign that something is wrong with your home. Cover up, use repellent and pick your outdoor hours wisely, and the season becomes much easier to live with in Bridgewater. If you're not sure what's biting you, EcoFusion Pest Control can inspect your property and point you in the right direction.