And the black flies, the little black flies
Always the black fly no matter where you go
I’ll die with the black fly a Pickin’ my bones
In North Ontar-i-o-i-o, In North Ontar-i-o
-Wade Hemsworth, “The Black Fly Song”[1]

And here we have a “black fly”, family Simuliidae, also known as “buffalo gnats” (either because of their humped back, or because they tormented buffalo. Maybe both). This one was on our kitchen window, and is evidently fairly old, judging by the tattered trailing edge of the wings.

There are three things about black flies that really annoy me:
1. You usually don’t get just one. You either have none, or hundreds, all after your blood[2].
2. They like to bite in really uncomfortable places, like right behind the ears, and are small enough that you need a small-mesh screen to keep them out[3].
3. The bites swell up a lot, itch like crazy, and take days to heal because of the little raw spot they have in the middle[4].

On the plus side, they are a lot more restricted in their breeding sites than mosquitos. The larvae need running water. It doesn’t have to be running fast, but it does need to flow continuously, because the larvae stick themselves to rocks and filter food out of the water that flows by[5]. No flow, no food[8]. This means that the huge numbers of black flies that we used to have in our yard had an easily identifiable source: the little spring and tiny stream that feeds into the swampy area just off the northwest corner of the house.

As far as what to *do* about them, it turns out that, like mosquito larvae, black fly larvae are susceptible to biologial control by Bacillus thuringiensis israelensis (BTI), which are bacteria that produce highly selective toxins that kill fly larvae. It is lucky that this is the same thing that works on mosquitos, because this means that I can actually *get* it (nobody seems to sell control products that are specific to black flies, because they are much more of a localized problem than mosquitos are). We used BTI granules on the little stream northwest of the house, then went ahead and spread it all over our swamp, and for good measure the neighbor’s swamp as well. We still have black flies, but now instead of hundreds of bites in a few minutes with clouds of them hovering around your head, we only have one or two bites after staying outside for a couple of hours. That’s tolerable.

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[1] Hemsworth based this song on his experience on a survey crew at the Little Abitibi River. This is actually not that far from here, maybe 500 miles to the east and a bit north. So, what he says about that location, is not too far off from what happens here.

[2] Actually, as is the case for most biting flies, only the females are after your blood. They need the protein (and maybe the salt) for their eggs. This comes from growing up in fresh water, which is notoriously lacking in nitrogen, and therefore also short of protein (which contains nitrogen).

[3] Some years ago, I had the bright idea that I could wear my beekeeping veil around the yard to keep out the biting flies. So, I put it on, went out into the garden, and watched the mosquitos bounce off. Success! But then, the black flies came. They would land on the mesh, squeeze through, and then head right for my ears. It barely even slowed them down, and the veil made it impossible to swat them. Gah! I ended up getting one of those fine-mesh “bug baffler” suits, which *does* have a fine enough mesh to keep out black flies. Which is important, because black flies are only slightly put off by mosquito repellents.

[4] I think the raw spot is caused by the way they get your blood. Instead of a nice syringe affair like mosquitos have, the black flies basically chew their way through your skin and lap up the blood, leaving an oozing hole when they are done.

[5] As per Merritt, Ross, and Peterson, “Larval Ecology of some Lower Michigan Black Flies” The Great Lakes Entomologist, 1978, pp. 177-208. This article was my introduction to the Michigan Entomological Society. For a society with a professional-quality journal, their dues are surprisingly reasonable, at only $25/year (I’m accustomed to organizations like the American Chemical Society or the Society for Mining, Metallurgy, and Exploration, both of which have annual dues in excess of $100/year, with journals that are no better than the one the Michigan Entomological Society puts out). I’ve been a member for a while now, and one of these days I’d like to make it to one of the meetings, except that they are usually downstate[6].

[6] Something that has occurred to me about the state of Michigan is that it would be kind of accurate to refer to it as the “Empire of Michigan”, since the Upper Peninsula has all the hallmarks of an overseas colony (separated from the main body of the Empire, was obtained as the result of military action and treaties that the inhabitants had no say in [7], has relatively little say in governance, mainly sends over raw materials, and it is a major undertaking to get from the colony to the homeland).

[7] Michigan ended up with the UP as a consolation prize, after losing the “Toledo War” to Ohio. In retrospect, and seeing what has become of Toledo over the years, the general consensus is that Michigan actually ended up coming out ahead of the game, although they didn’t think so at the time.

[8] Wade Hemsworth was probably in one of the worst black-fly spots in Canada, since they were surveying around a river with enough flow to be suitable for a hydroelectric dam. It must have been paradise for all those black fly larvae.