Local's bane for the female blackfly runs deep

Posted: Friday, February 26, 2010

Our peculiar February weather has me thinking of April. And that makes me think of songbirds starting to nest and flowers beginning to bloom, although surely it is still too early. But the insects are starting to fly; on recent walks we have seen several cool-weather flies in action.

Photo By Bob Armstrong
Photo By Bob Armstrong

Usually I write about things that I like: Hiking and snowshoeing, reading animal tracks and signs, birds and mammals and fish, and even plants. But just recently I was reading naturalist Berndt Heinrich's book "Summer World" and some of his observations reminded me of something I hate - blackflies.

Long ago, as soon as university classes were over in May, my husband and I would load up the car and head north to canoe for two or three weeks in Quetico Park in western Ontario. Sometimes there would still be ice on the fringes of the lakes, but it was a grand time to watch spring come to the north woods. The early spring flowers would be in bloom and the migratory birds would arrive and fill the woods with their songs and color. Hungry lake trout and walleyes would find my lures before we paddled into camp for the night.

The down-side was that in some years, or in some places, the adult blackflies were emerging from the streams where they spent their larval life, and they were ravenous! They especially liked to crawl up behind my ears and gnaw away, unfelt, until the blood ran down into my collar, where it dried into hard, scratchy rims that scored my neck. Later, the fly-chewed flesh would swell up until my ears flared out from the side of my head and my jaw could barely open. At that, I got off easy: really bad attacks have been reported to kill deer and humans. As in mosquitoes, it is the females that are hate-ably voracious, needing a blood meal to make their eggs.

Around here, there are blackflies too, but I've never encountered them in the swarms that we found in the Quetico. Some local folks call them "white-socks." When we were sampling stream invertebrates in the course of a study of American Dippers, we'd sometimes see blackfly larvae, little bowling-pin-shaped squirmers attached to the rocks. I had to control the impulse to crush them, remembering that those larvae are bird food. And also the male blackflies can help pollinate flowers.

Another pet hate for the insect clan involves punkies or no-see-ums, which are biting midges. Again, it is the females that are blood-thirsty; males may visit flowers or not feed at all. So tiny they can squeeze through all but the finest screens, they make it imperative to have that fine screening on your tent. Their common name makes it clear how insidious their attacks can be-not seen, not heard, but oh my how they are felt!

I remember a kayak-camping trip on Chichagof one summer. I went to a stream to get some drinking water and was kneeling there, pumping the slow-acting filter. The sun had toasted the tips of my ears to a well-tenderized, peeling condition. And there, of course, is where those (unprintable) no-see-ums attacked. Over and over again! Well, the filtering process was cut short, until some protective covering was found.

However, there are other kinds of midges, in a different taxonomic family, that don't bite, and some of these are very important food for animals. The larvae are generally aquatic and can be good prey for fish. On the shores of Lake Huron, the adults emerge en masse in spring, forming huge mating swarms near the shore. They do this just as waves of migrating warblers arrive from the south.

Researchers have found that shoreline populations of spiders increase in response to the burgeoning hordes of midges. The arriving warblers feed heavily on both midges and spiders, and they gain weight rapidly. Thus the birds regain the energy lost on the northward flight and put on enough fat to make the next leap north or to start the process of nesting nearby.

So when I'm growling and snarling at nasty little varmints, I have to remember that they have some important ecological roles and a valuable place in the ecosystem.

• Mary F. Willson is a retired professor of ecology.



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