True story: North Country deer flies away
Sunday, July 14, 2013 - 8:33 am

By PAUL HETZLER

With some things in life, if you have one, you have one too many. Toothaches, flooded basements, difficult break-ups and traffic accidents are but a few examples.

I happen to think that deer flies, those hard-biting pests with a knack for moving in at the instant your hands are full, fall into that category as well.

All it takes is a single deer fly noshing on your face while you try to land a fish or set up an extension ladder to make your eyes cross in pain and frustration.

Because of their one-is-too-many status, it's easy to miss the fact that there are significantly fewer of them this year. It's the nature of an irritant that its presence is readily noticed, but its absence often doesn't register.

Every frazzled, sleep-deprived parent knows that moment of panic when they suddenly realize it's been quiet for too long, and the kids are probably crayoning the wall, cutting up the curtains, or engrossed in some equally endearing project.

While deer flies were insufferable last summer, this year I gardened in mid- to late June for quite a while before I noticed something was wrong—it was too quiet. There were no deer flies!

Of course that was the moment one began orbiting my head, but it was alone. Since then more have come out, though nothing like normal.

Where deer flies are concerned, a summer like this is as close to a break as we'll ever get, because their biology makes it impossible to control them with insecticides.

Seems like it would be good to find out where they went, in case we can send even more of them there next year. I suspect their low population has a lot to do with last summer's weather.

Like horse flies, deer flies spend most of their life as aquatic larvae, usually maturing in one season but occasionally taking two or even three years underwater before reaching their nasty adulthood for a month of mating and egg-laying.

The female deer fly seeks out shallow muddy places in which to lay her eggs: pond edges, stream backwaters as well as every little marshy area and mud hole.

Wet years are good for them; dry years, not so much. In 2012 many traditionally wet places shrank in size or dried up completely. Ponds and marshes retreated; ephemeral streams evaporated earlier than usual. Many larvae that hatched in such locations early in the season would have become dry and lifeless by August.

Although swallows, flycatchers and dragonflies might not agree, perhaps the only positive effect of the drought of 2012 is a (relative) dearth of deer flies in 2013.

While the population loss varies by location, and there are still more than enough of them to go around, deer flies are much less intense than in most years. To the throngs of deer fly larvae that perished last year, I say: deer departed, you will not be missed.

Paul Hetzler is a forester and a horticulture and natural resources educator for Cornell Cooperative Extension of St. Lawrence County.