Flies of the Upper Peninsula
If you spend any real time outdoors in Michigan’s Upper Peninsula, you’re going to meet the flies. Not just one kind, no. You’ll encounter an entire cast of them, each with their own season, habitat, and personality. Knowing when and where they show up as well as how to deal with them can make the difference between a miserable outing and a great one.
This isn’t about avoiding the outdoors. It’s about understanding it. In this blog post, I set out what you’ll face, when you’ll need to be ready, where they can all be found, and important intel for preparing yourself so you can be one with the flies. As an avid UP brook trout fisherman, I can tell you from experience, there is no substitute for local knowledge and preparation. Let’s face the flies.
Mosquitoes
Season: Late May through September (peak: June–July)
Where: Anywhere with standing water like wetlands, low forests, calm evenings
Mosquitoes are the state bird of the UP. Let’s be real, if you’re in the woods in the summer, you’re going to have to deal with mosquitoes, especially if it is warm, humid, and still. Early season hatches can be intense, especially after snowmelt or a rainy spring.
Local knowledge:
Calm, warm evenings are the worst. A light breeze and cool air makes a big difference.
Deep woods and wet areas hold mosquitoes longer into the summer.
They taper off significantly by late August unless it’s been a wet year.
What works:
Loose-fitting clothing (this will be a theme)
Head nets when it’s bad (head nets take away from the view with having to look through the mesh)
Pro tip: wear a baseball cap underneath to keep the net away from your face
NATURAL repellents (Iguana Oil, Murphy’s Repellent)
I am a strong proponent of natural insect repellents that work just as good as synthetic repellents and don’t give you cancer
Black Flies (gnats)
Season: Mid-May through late June (short but intense)
Where: Near moving water like streams, rivers, and shaded forests
Black flies are infamous in the UP for a reason. They hatch in huge numbers and go straight for your ears, hair, and neck like little gemlins. People often use the word “black fly” to describe stable flies (see below) - I’ll call this the great Yooper fly argument.
Local knowledge:
Their season is brief but brutal. You must plan accordingly - I’ve heard stories of fishermen being driven crazy, covering themselves in mud as a way to find relief from the torment of black flies.
They prefer shaded, damp environments and are less active in open, sunny, breezy areas.
Once they’re gone, they’re gone - like Keyser Soze in The Usual Suspects.
What works:
Head nets are the single most effective solution
Wear a hat with a hood to keep them off your neck
Repellent helps a little, but not enough to rely on
Stable Flies (“Beach Flies” or “sand flies”)
Season: Late June through August
Where: Lake Superior shorelines, especially sandy beaches
Stable flies are the ones that surprise people. They look like houseflies but they bite and they can really hurt. I’ve seen children (and some adults, though I won’t say who…) cry from stable fly bites. They love your ankles and lower legs.
Local knowledge:
A south wind is the trigger. It pushes them toward the Lake Superior shoreline, where they concentrate. You should proceed with extreme caution to the beach on a south wind day when the stable flies have hatched.
On a calm or north wind day, the same beach can be perfectly fine.
They are most active in full sun, especially on open sand.
What works (and doesn’t):
Wear long loose pants or high socks because physical barriers matter
Pro tip: they are attracted to light colors and will completely cover a white shirt
Choose your days: wind direction matters more than anything
INSECT REPELLENT IS INEFFECTIVE! You can literally spray Backwoods Off with high concentrations of DEET on these little demons and they’ll come back for more.
Deer Flies
Season: July (peak), sometimes into early August
Where: Open trails, wetlands, edges of forests
Deer flies are aggressive, persistent, and highly visual hunters. They circle your head and aim for any exposed skin or hair. If mosquitoes are like the prop planes of flies, deer flies are like the F-16.
Local knowledge:
They’re most active in sunny, low-wind conditions
They’re attracted to movement and slowing down can sometimes reduce attention or allow you an opportunity to smack ‘em
They tend to be worse in open, marshy terrain than deep woods
What works:
Head nets again, to keep them out of your hair
Light-colored hats (they’re less attracted than to dark colors)
Letting them land and then taking them out (but be quick, they stick like velcro and pack a punch when they bite)
Horse Flies
Season: Mid-summer (July–August)
Where: Wetlands, near water, open sunny areas
Horse flies are larger and less numerous than deer flies, but their bites can be more painful. They will ruin a good swim or boat ride out at camp. It is not uncommon for someone to jump in a lake to avoid the bugs only to have horse flies attack your bobbing head.
Local knowledge:
They rely heavily on sight and movement so be patient when trying to rid yourself of a deer fly
They’re strongest on hot, sunny days
You’ll usually encounter them around water, especially if you’re wet yourself
What works:
Horse flies are probably the easiest to kill so let them land and then time your smack
Loose clothing helps, but they can bite through thinner materials (I’d rather be hot than get bit)
Goad them into a false sense of security and then destroy them
No-See-Ums (Biting Midges)
Season: Late June through July
Where: Damp, shaded areas; near water
These are tiny, almost invisible, flies but their bites can be intensely irritating. They are small enough to find their way through window screens. If your windows are open and you came in from outside to avoid the mosquitoes but you’re feeling like your skin is rashy (like hot and itchy), you most likely have no-see-ums.
Local knowledge:
Most active at dawn and dusk
Often overlap with mosquito conditions
You’ll notice the bites more than the insects themselves since they’re so small and hard to see
What works:
Full coverage clothing like long pants and a loose hoodie
Natural repellents can help, but coverage needs to be thorough
Completely close windows and tent flaps that have screens
General Strategies for Hiking in Fly Season
1. Dress for it, don’t fight it
This is the number one piece of advice. Loose-fitting, specific-colored clothing is your best baseline. It reduces bites across multiple species and keeps you cooler.
2. Always carry a head net
Apart from having the right clothes, a head net is the single most effective lightweight piece of gear you can bring. When things get bad, it changes the entire experience.
3. Pay attention to wind and terrain
Breezes reduce mosquitoes and black flies so summiting is usually a nice deterrent (plus you are typically rewarded with a view)
Wind direction can make or break a Lake Superior beach day, especially with stable flies
Open vs. shaded terrain matters depending on the species
4. Timing matters more than toughness
You don’t get extra credit for suffering through peak mosquito or black fly season. I am typically covered head to two by clothing while brook trout fishing but one time I forgot my gloves and after 10 minutes I almost threw up because the mosquito bites on my hands were so intense.
5. Keep moving (most of the time)
Many biting flies key in on stationary targets. Hiking steadily is often better than stopping frequently in buggy conditions.
Final Thought
The flies are part of the ecosystem here. They feed fish, birds, and everything in between - thank your local dragonfly, they’re doing the Lord’s work. Even Yoopers can’t stand the bugs, but understanding them lets you move through the UP with a lot more confidence and a lot less frustration. Sometimes its a mindset, but most of the time its preparation.
If you plan well, you can still have incredible days outside even in the thick of it.
