Something Wild: Celebrate the Plague of Black Flies

May 5, 2017


Well…maybe not. 

First off, let’s identify that buzz, it doesn’t emanate from a louse, it comes from black flies. Everyone’s favorite bug to hate this time of year. As hours of daylight increase, temperatures start to rise, making conditions just right for black flies, and that’s worth celebrating.

There are places in the state that don’t have black flies. And the reason that is the case comes down to something you heard in your imaginary walk through the woods…the nearby stream. Whereas mosquitoes thrive in stagnant pools, puddles and even bottle caps, black flies need cold, clean, open, running water. So the places that don’t have black flies tend to be urban and suburban developments that  have had to route those waters underground or into culverts and the like. As a result, black flies have no place to lay eggs.

That may not sound like such a bad thing on the surface, but black flies serve an important ecological role. In the fall, they lay their eggs in water, where they develop and spend the winter. While they’re in the water column they act as a sort of filter, feeding on tiny pieces of vegetation, converting them into protein. And they in turn are an important source of food for fish.

And, of course, once they become airborne in the spring, birds – like warblers and thrushes – rely on them to feed newly hatched chicks. Black flies are also important to birds that are just stopping off en route to nesting grounds further north. And if those flies suddenly aren’t there, the birds are going to have trouble fueling up to continue their journey north. 

Additionally, their presence is an important indicator of a healthy eco-system, upstream. If they’re around, then so too is clean, clear, cold water; water that has been fostered and filtered by a healthy forested watershed. So yeah we should celebrate the emergence of black flies each year.

Credit smilla4, Flickr Creative Commons

  If that’s not enough consolation to soothe your throbbing bug bites consider this, it is a short season nominally from Mother’s Day to Father’s Day, though it has been creeping earlier in the year. But once the mercury levels rise beyond a certain point, black flies disappear.

And, only half of the flies you see are trying to bite you. The females are in search of blood – to fuel their reproduction process and nourish the eggs. The males are probably just following the females around, but not biting.