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The Definitive Guide to New Hampshire Black Flies [Infographic]

Updated: Oct 14, 2022

new hampshire black flies
Definitive Guide to New Hampshire Black Flies

Yeeehaaaa! Winter is OVER! The days are getting longer, April showers bring May flowers, the days are warm and the nights are cool.

Don't you just LOVE spring? I do and so do the black flies, or as some folks call them, May flies. While you're ducking the black flies, check out 7 Perfect Summer Days in North Conway, NH.

Don't let the black flies keep you from enjoying the outdoors. There are many suggestions later on in this article to keep you black fly free!

When I was a kid, they used to say that the black flies in New Hampshire come out for two weeks starting around Mother's Day and almost disappear by Father's Day. Those dates are pretty accurate.

Like mosquitoes, it's the egg laying female black flies that bite and the males are the first to hatch out in the spring. Both male and female black flies are a food source for fish, birds and my two backyard chickens!

The Cooperative Extension at the University of New Hampshire states that there are approximately 40 species of black flies in New Hampshire but only 4 or 5 are human biters. Even thought most species don't bite, they are extremely annoying when they swarm your head and neck!

Unlike mosquitoes, black flies hatch in clean, clear and non-polluted running water like streams and rivers. A healthy population usually coincides with running water that is not polluted with organic pollutants.

I've chatted with many hay guys (local men that make their living by growing and baling hay) in North Conway who swear they do not get bothered by black flies any more.

Did they drink a magic potion? Nope, apparently you can build an immunity to the dreaded New Hampshire black flies!

I heard a story once, not sure if it's a rural legend or not. (Get it? Rural legend!)

Anyway, the story is about a man that went cross country on horseback wearing a black hat. He claimed he wore his black hat to attract the black flies and when he caught enough on his hat, he gathered them and gobbled them up.

He claimed that eating black flies gave him immunity.

Whether this legend is true or not, according to the University of Maine's Cooperative Extension there is some information about immunity being fact.

“Generally black fly bites cause some itching and minor swelling from the first few bites of the season, following which an immunity develops, with subsequent reduced reactions. Nonetheless, even individuals who have lived all their lives in black fly country and are exposed every season, can have greater effects if they get an unusually high number of bites on their first exposure of the season, or have some significant change in their physical condition or medical status.”

NOTE: They do not mention eating black flies. :)

Unlike mosquitoes, New Hampshire black flies breed exclusively in slow to fast moving, clear water. (You might want to plan your hikes on trails that do not follow the path of a river or mountain stream!)

​In spring, when the females have feasted on a blood meal (hopefully, not your neck!) they lay their eggs on plants and grasses in rivers and streams or distribute them over the surface of the water. The eggs hatch out under water and the larvae attach to granite, leaves, grass, roots or other submerged objects.

The larvae pupate underwater becoming mature and when reaching adulthood, they ride bubbles of air to the surface and fly away.

Starting the cycle again, adults mate near the breeding site and females, who need a blood meal so they can lay eggs, begin their search for blood again. (Keep reading, the list of how to avoid black flies is coming!)

The eggs remain submerged in rivers and streams for the entire winter in the first case. Once the water temperature reaches 40-50 degrees F, they begin to hatch out.

The maturation process starts in early spring with the larvae development, while the adults emerge as late as early summer to begin the cycle again.

A few species of black flies complete the cycle more than once a year! Fortunately, the ones that hatch out in fall will swarm but usually not bite.

The second black fly life cycle overwinters in the larval stage.

Adults emerge from late April through May and females deposit eggs in May and June and remain in the water until fall when they hatch.

OutIets of ponds, lakes and streams are usually the favorite breeding grounds of the biting black fly species, This may be due to the readily available food sources.

Depending upon where you happen to be in New Hampshire, one of the state's big biters, the "white-stockinged" black fly emerges in May and can remain active in the higher elevations (North Conway is not a higher elevation town) until July!

Last but not least, the late season species are most annoying along the larger rivers in northern New Hampshire in August and September.

They tend to swarm around your head in large numbers but don't fear, they are not usually biters!

1. Black flies are MOST active midmorning and dusk so plan your outdoor activities accordingly. If you get bitten, the area around the bite will get red, swollen and itchy!

Mix 2 cups baking soda in a warm bath and soak when you get home. It'll make the bites feel better plus you'll get rid of the smell of bug spray!

2. Plan a shopping day or inside activities on stormy days because black flies tend to be more active during those times.

3. Black flies are attracted to darker shades of clothing. Leave them at home! Wear light colors and make sure to wear long sleeves and pants. You can tuck your pants into your socks to make sure nothing (including ticks) sneaks up your leg!

4. Insect repellent containing DEET is very effective in keeping black flies away but is thought to be unsafe for use on human skin. Some folks can be especially sensitive to DEET. Use of this pesticide on infants is NOT recommended.

Alternative repellents can be made from natural ingredients such as citronella, lemon eucalyptus oil, Listerine, citrus essential oils and other natural products.

I make bug spray from natural ingredients and use it on me and my horses.

Here's my tried and true black fly repellent recipe for a large spray bottle:

  • Get a good quality spray bottle or screw cap vessel

  • Fill about half-way with warm water

  • Add a small squeeze of Dawn dish soap (more if you're making a quart)

  • Add about 1/2 cup Listerine anti-bacterial mouth wash

  • 1/2 cup vinegar

  • 1/2 cup witch hazel

  • About 20 drops of clove oil, rose geranium oil, citronella, lemon eucalyptus oil, lavender oil, neem oil, cedar wood oil, and castor oil.

I use all of those oils but if you cannot find them, use what you have. I believe that citronella, dish soap, lemon eucalyptus, and Listerine are essential ingredients.

The initial cost of all the oils is pricey but each bottle of oil is good for many batches of spray. I've tried just about everything on the market and spent tons of money on pricey bottles of goop that didn't work. My homemade brew works!

5. Keep moving. You heard me, don't stop! Black flies are lazy and won't keep up with you if you walk, hike, kayak or bike at a good pace. You'll burn more calories and be able to have that great dessert at the restaurant if you do too! If you must stop for long periods of time, head nets are very inexpensive and work like a charm. Warning - they are a fashion statement of the worst kind!

6. Do not go into the woods with any scent on your body or clothing. Ever. :) The list of no-no's includes; hairspray, scented deodorant, scented body lotion, perfume, scented soap, scented shampoo or creme rinse and drum roll please - NO scented laundry soap!

7. Don't you just love the sound of a babbling brook or a rushing river? NOT during black fly season you won't! Black flies breed and grow up in moving water. Plan your hikes on trails that do NOT follow alongside any moving water!

8. Wear net clothing. The most popular attire for keeping black flies at bay is a head net.

They are cheap and effective. Just pop it over your head and either let it lay on your shoulders, chest, and back or cinch it close to the fabric of your shirt.

​9. Last, but certainly NOT my favorite way to avoid black flies is to put out a bird feeder.

The black flies will be attracted to the bird food and the birds will snack on the flies BUT in the north country, you'll attract bear too. FYI, Fish and Game can and will make you take down a bird feeder during the summer.

Dozens of bear are euthanized every year in the North Conway, NH area because of bird feeders. Bear are lazy and would rather eat your bird food and break into your garage to get your trash than forage for berries. When that happens, they get labeled as "nuisance bear", are trapped and shot. Yep, shot. Sad truth. Don't put out bird feeders when bear are out of hibernation, please!

For those that like visuals, here is an Infographic showing 8 awesome ways to avoid black flies.

new hampshire black flies
Avoid New Hampshire Black Flies

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