In summer every year, something remarkable happens in North Bay. As the evenings warm and the lake begins to shimmer at sunset, millions of delicate-winged insects emerge from the bottom of Lake Nipissing and given they are highly attracted to light, make their way in swarms to the cities streetlights and settle on storefronts along the waterfront. Locally known as shadflies (also known as mayflies or fish flies), their arrival sparks conversation, curiosity – and sometimes complaints.
But what if, instead of being repelled, we chose to celebrate them? After all, these fascinating creatures are short-lived and sign of a healthy eco-system – so these visitors deserve a little appreciation – let’s find out some fun facts about Shadflies.
Shadfly by sunset – photo credit: Eric Boutilier
1. They’re Named After a Fish
The Canadian name “shadfly” comes from the Maritime fish, the shad. The migration of shad up eastern rivers historically coincided with the mass hatch of these insects – and the name stuck.
While technically a type of mayfly, in Northern Ontario they’ve earned their own local identity. Like so much of North Bay’s culture, even our insects carry a story rooted in nature and history.
2. They’re a Sign of a Healthy Lake
This may be the most important reason to celebrate them.
Shadfly larvae live underwater and cannot tolerate high levels of metals or pollution. That means a large hatch is actually a powerful indicator of a clean, healthy lake or river ecosystem.
When you see shadflies along the shores of Lake Nipissing, you’re witnessing proof that the water system is thriving. Their presence is environmental reassurance – nature’s way of saying things are in balance.
In other words: the bigger the hatch, the better the health of our lake.
3. They Symbolize the Brevity of Life
Shadflies have been used in art and literature as symbols of life’s fleeting beauty – and for good reason.
Photo credit by @garcamart
The adult insect lives for only about 24 hours after hatching. They emerge, swarm, mate, lay eggs, and complete their life cycle in a single day.
It’s a powerful reminder to slow down and appreciate the moment. In a place known for sunsets over Lake Nipissing and peaceful shoreline walks, shadflies offer an unexpected but meaningful lesson: life is short – soak it in.
4. They Feed the Ecosystem (and Us!)
Shadflies are an incredibly important food source for fish, birds, and other wildlife. In fact, their emergence provides a seasonal buffet for the entire ecosystem.
Healthy fish populations – including those prized by anglers – rely on this burst of protein.
Even more surprising? In some cultures, dried insects are ground into protein-rich powder and added to food. While that may not be on most North Bay menus, it highlights how nutrient-dense and valuable they truly are.
They’re not pests – they’re nourishment.
5. They’re So Big, They Confuse Satellites
In some areas, shadfly swarms are so massive that weather satellites have mistaken them for storm clouds.
Think about that.
The hatch can be so significant that it shows up like a weather system on radar. It’s one of the most dramatic and unique natural events of the season – a phenomenon that draws attention well beyond our shoreline.
That’s not gross. That’s impressive.
6. Yes, They Can Be Slippery — But They’re Harmless
Occasionally, large accumulations of shadflies on bridges and roads can create slick surfaces. Municipal crews are well-prepared for seasonal clean-up, and the hatch itself is short-lived.
Most importantly, shadflies do not bite. They don’t sting. They don’t damage property. They don’t even have functional mouths as adults.
Their entire purpose is reproduction and completing a natural life cycle – and then they’re gone.
A Celebration of Nature’s Rhythm
Living in a four-season destination like North Bay means embracing nature in all its forms – brilliant fall colours, snowy winters, spring blooms, and yes, shadfly season.
Rather than viewing them as an inconvenience, we can see them for what they truly are:
- A sign of clean water
- A vital part of the food chain
- A fascinating natural spectacle
- A reminder to appreciate fleeting moments
They are part of the rhythm of the lake and the story of our city.
So the next time you see shadflies dancing in the evening light along the waterfront, pause before turning away. Look closer. You’re witnessing one of Northern Ontario’s most extraordinary natural events – proof that our environment is healthy and alive.
In North Bay, even the smallest creatures have a big story to tell.