Biting fly forecast depends on Maine’s changing rain patterns

If you think you’re being bitten by more deer flies, horse flies or black flies this summer, you’re not alone — maybe.

These flies slash their way into human skin with scissor-like mouthparts looking for a meal, leaving painful bites behind. There are dozens of species of black flies and hundreds of deer and horse flies with different regional distributions, although not all of them bite people.

How many will bite you this year probably depends on the number of short, intense rain events that happen where you live. This precipitation pattern is becoming more common in Maine, replacing longer storms that leave less standing water, according to Jim Dill, a pest management specialist with the University of Maine Cooperative Extension.

Deer flies and horse flies are in the same scientific family, and they breed in similar conditions. Standing water with decaying plants in it — such as a soggy hayfield — is an ideal site for them, Dill said. They prefer the edges of watery areas.

The state’s climate council reported this year that Maine is getting wetter and seeing more intense precipitation because the hydrologic cycle has intensified, meaning water cycles through the environment faster than it used to.

This summer hasn’t been unusually wet overall, but when it comes to flies, the problem is the large doses of rain all at once, Dill said. Different patterns across the state mean some people aren’t bothered much this year while others are facing more flies.

What about mosquitoes? Heavy rain may not always mean more of them. They tend to breed in areas like blocked gutters, birdbaths and other receptacles that have collected algae. A downpour would wash them away if these items overflow, but could also create new habitats in unexpected places, such as forgotten buckets or pots, around your yard.

These weather conditions help out another kind of insect that might alarm you: thousands upon thousands of tiny flies swarming and breeding in a cloud. They are chironomids, or non-biting midges, which should disappear in a few days.

Black fly populations prefer clean and fast-moving water, so their numbers change much less with the rain. Unless an enormous storm washed out a stream and muddied it, they won’t vary as much.

Whatever fly bothers you this summer, there are unusual deterrents to try. You could make a baby oil-covered helmet trap, fill a spray bottle with repellent of Epsom salts, mouthwash and stale beer , or rub your clothes with a dryer sheet .