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Black Flies – What You Need To Know

What do you need to know about black flies? Well, they bite, and it hurts. Those bites leave itchy red bumps, so you’ll feel it if one does bite you. But if a swarm takes a liking to you? That can be dangerous. 

Black flies are not mosquitoes, but it’s easy to mix them up. Black flies – also known as “Buffalo Gnats” – are similar to the much-maligned mosquito, but with some key differences that change how you should handle and perceive them.

1. Black flies find prey the same way mosquitoes do.

Black flies track prey the same way mosquitoes do. They sense and are attracted to CO2, which can be exhaled or found on skin. To counteract this, keep cool (so you don’t breathe as heavily or sweat as much) and wear loose-fitting clothing when you know these pests are active. This can vary completely depending on where you live, so make sure you know what kind of pests are in your neighborhood before you head out.

2. Black flies bite in the day.

While mosquitoes love dawn and dusk for feeding time, black flies will bite you in the middle of the day. If your town has black flies as residents, you have to keep your guard up and your repellent handy every time you go out. Picaridin-based repellents like Stay Away Mosquitoes are effective, and they’re also gentle on skin! The good news is that, unlike mosquitoes, black flies don’t enter human buildings, so you can relax if you’re staying in for the night.

3. Black flies don’t spread disease, but they’re still dangerous.

Black fly bites are painful and can cause severe allergic reactions in some people, and they can be very dangerous in swarms to livestock, people, and pets. However, at least in the United States, they aren’t known to infect humans with any diseases like West Nile. You’re better off not risking it, though. In other parts of the world, black flies are one of the leading causes of blindness thanks to a parasite they often carry. 

4. Black flies are fussy with where they lay eggs.

Unlike mosquitoes, black flies only lay their eggs in clean and fast-moving water, so unpolluted streams are common nurseries. Most people don’t have clean streams near their home so you probably don’t have to worry about black flies in your backyard. The bad news is that because they have stricter requirements for egg-laying than mosquitoes, black flies have evolved to travel further for their blood: up to 40 miles from their breeding grounds in some parts of the world!

5. Black flies are actually important for the ecosystem.

While mosquitoes only have some niche benefits for the earth, black flies have an important role to play in the ecosystem of streams and rivers, as their offspring feed dragonflies, trout, and other fish that can be found in similar environments.


So, how can you protect yourself? Many of the same tips for protecting yourself from mosquitoes work for black flies too! Here’s our recommendations for staying bite-free.

Here’s how you can avoid black fly bites:

Black flies are a little easier to avoid than mosquitoes. You don’t have to worry about them if you stay indoors, and they’re only active during the day (often soon after sunrise and shortly before sunset) so you’re safe to crack the windows open after dark. If you do go out, make sure to protect your skin with light-colored clothing that covers as much of your skin as possible. Since black flies often go for the hairline and the back of your neck, it can be tough to protect yourself effectively. 

Or, you can stay bite-free while living your life the way you want to, wearing what you want and going out when you want. Just use a proven repellent, like Stay Away® Mosquitoes. It’s not just for mosquitoes: made with picaridin, Stay Away Mosquitoes can repel biting flies (like black flies), mosquitoes, ticks, and chiggers all day long. It’s also super gentle on skin, meaning it’s safe for the whole family when used as directed–pregnant women and children included. So get outside, enjoy nature, and tell the black flies and their pals to stay away.

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