Why Are There So Many Black Flies This Year In Minnesota?

If mosquitoes weren't bad enough, we've also entered our black fly or biting gnat season in Minnesota. We set some traps out in our yard, and I was shocked at how many thousands of black flies we had already caught in just a couple of days. They seem to be everywhere! The surge of black flies this last weekend at the lake caused us to flee indoors!

These black flies or biting gnats are most common in Northern Minnesota, and especially close to Lake Superior. Black flies lay their eggs in streams and rivers. Once the larvae mature and become adults, they quickly mate. Then the female fly needs to find a blood host in order to lay her eggs. That's where you come in! They'll swoop down and take a chunk out of you.

The good news is that they typically are pretty harmless. They don't spread diseases, and the bites clear up on their own. However, they can be very itchy and irritating.

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Minnesota was looking at having a below-average black fly season this spring, but recent heavy rains have turned a below-average season into a pretty strong one. We had a very dry spring, but July has proven to be wet across Minnesota, with some areas receiving significantly higher rainfall than average.

The extra moisture means more water in streams, rivers, and creeks. This increases the breeding ground for the black flies, leading to a surge in numbers.

Protect yourself by wearing light colored clothing, applying repellent with DEET, and consider using fly and pest traps.