“More likely, you’ll go blind and starve to death. Or you might go crazy. That’s happened to guys up here before.” The Bay (formerly Hudson’s Bay) store manager amused himself by scaring my friend and me with tales of the north woods through these warnings about black flies. It ended up being truer than we’d imagined.

Truer, at any rate, than the story he told us about the time he was sleeping under his boat and a polar bear came sniffing around. He thought he was done for, but when the bear got a whiff of his stinking feet, it let out a cough and took off running. The tale is obviously a lie and a stupid one at that, yet here it is, stuck in my mind like a memory I’m almost ashamed of.

Sometimes you’re gullible, and sometimes it’s nice to pretend to be because it makes someone else happy to think they’re fooling you. It might even make them happy if they know you’re going to the bother of pretending to be fooled by them. I’m glad the Bay store manager got some laughs then because after we lost our canoe and started traveling overland, we got our own taste of the black fly experience, and they got a pretty good taste of us, and by that time, we weren’t laughing.

Dozens of species of black flies in the genus Simulium—many of them distinguishable only by examining their chromosomes (in other words, they all look alike)—are the curse of the north during late spring and early summer. While both males and females feed on nectar, just as with mosquitoes, it is the female that takes blood meals in order to nourish her eggs. Unlike mosquitoes, however, black flies don’t merely poke their proboscises into our skin. With the aid of cutting tools, anesthetics and anticoagulants to keep the blood flowing, black flies literally saw their way into us, leaving large and irritated welts along the hairline, ears, cuffs, waistbands and other cozy human nooks.

With the aid of cutting tools, anesthetics and anticoagulants to keep the blood flowing, black flies literally saw their way into us!

Satiated with blood, the female black fly deposits her eggs near the edge of a flowing stream, or flies over it, dropping them into the water like a World War II bomber, or maybe more like an evil stork. When the eggs hatch, the larvae attach themselves to rocks with silk they spin from their saliva. This silk is so strong it can hold a black fly right at the very edge of a waterfall. And if a larva loses its rocky footing, the silk thread streams out like a lifeline, preventing it from being completely carried away by the current.

Once attached, black fly young orient themselves facing upstream and net passing food particles in elaborate fans that extend from their heads in a manner reminiscent of filter-feeding sea creatures like corals. In suitable streams—moving, well-oxygenated water is the principle requirement, so ironically, their presence is a sign of water quality—larvae may be so numerous that the rocks they’re attached to appear to be covered by moss. As polluted streams are cleaned, particularly of oxygen-sapping organics like raw sewage, they become black fly habitats. Populations now seem to be flourishing in many parts of the state.

After a period of days or weeks, depending on the species, each larva goes through a second stage of development as a pupa in an underwater cocoon, until finally, the adult emerges, popping to the water’s surface in an air bubble. It then looks for a mate so the cycle can begin again.

Like mosquitoes and many other biting insects, black flies can carry diseases. In warmer climates, an insidious parasitic roundworm passes into people through black fly bites. These worms develop inside the human eye, causing the disease onchocerciasis, commonly referred to in Africa and South America as “river blindness.” In 2017 it was estimated that over 220 million people needed chemotherapy to combat the parasite.

Here in the north, black flies are mostly an annoyance. There are parts of Michigan and Canada that I won’t visit during the height of black fly season, because I don’t enjoy barricading myself behind a head net and repellents. Sure black flies are part of the natural experience, but so are many other things I don’t seek out, like poison ivy and rattlesnakes.

And as our Bay store man pointed out, that early July in northern Ontario, black fly bites can be dangerous if you’re out in the wilderness. Though we doused ourselves with 97% DEET, our hungry attackers explored every inch of skin and clothing as they sought some weakness in our defenses. At one point, we were actually black with flies, and one of my friend’s eyes swelled shut. We could easily have been injured stumbling blindly over moss-covered rocks and logs, or just plain driven mad by the infernal swarm. In rare cases, death may be the result of exsanguination or loss of blood due to too many bites. That’s one way I’d definitely prefer not to go.