That’s how many black flies, or biting gnats, were captured near Jordan during one night in one trap.

And there were still gnats swarming to get in when the Metropolitan Mosquito Control District worker picked up the trap the next morning.

“We’ve seen some numbers in traps around the area that have been just off the scale. In the 23 years I’ve been here, I don’t think I’ve seen a number like that,” said Mike McLean, MMCD public affairs coordinator.

Usually, during treatment to eliminate gnats, traps used to gauge their population will capture 100-200, or maybe 1,000 during an infestation.

The quantity of the gnats found in the Jordan trap forced the MMCD to add an extra “0” to its database.


Gnat-mageddon started about three weeks ago.

Since then, woe to anyone attempting to mow the law, take a hike or play a round of golf.

Unfortunately, with the high waters around the state, the MMCD has been unable to treat for black flies (not to be confused with the larger houseflies). “We ordinarily keep the numbers to something approaching reasonable,” McLean said.

The MMCD, with cooperation from the Minnesota Department of Natural Resources, treats black fly larvae with Bti, a naturally occurring soil bacteria. However, sustained river flooding has made the process difficult.

Now, with the water levels dropping, it's easier to treat for gnats. And recent windy days have dissipated the gnats.

McLean expects the gnats, which have a two- to three-week lifespan, to decrease by the weekend. “We don’t see a lot of gnats being added to the population,” he said.

In areas that aren’t treated, the gnat population usually drops off by the end of June, McLean said.


Gnats, unlike mosquitoes, thrive in moving water, like rivers and streams.

Gnat larvae stay attached to rocks, grass or twigs, filtering nutrients from the water. Ultimately the gnat pupa gathers a “a little beach ball of air” and launches itself to the top of the water, McLean said.

Like female mosquitoes, female gnats feed off blood to develop eggs. However, gnat bites are nastier than mosquito bites.

Mosquitoes use their proboscis to burrow under skin and suck out blood. Gnats are less subtle, using scissor-like device to cut through the skin, then lap up the blood. They drop in an anticoagulant for good measure, to keep the blood flowing, McLean said.

While the bites usually leave a raised bump and itch, Minnesota gnat species don’t carry disease.

However, they can have an effect on wildlife through sheer numbers, McLean noted. In northern Minnesota, loons have been known to leave their nests due to gnat intensity.

Closer to home, at the Minnesota Landscape Arboretum, Twin Cities Metro Osprey Watch believes the newly hatched chicks viewed on the popular osprey nest camera succumbed to black flies.

“It’s not just humans they’re after. They’re a pest of a lot of different mammals, and birds as well,” McLean said.


There is one good thing about gnats.

“They do better in rivers and streams where water quality is improving,” McClean said.

So, when someone says, "Gnats weren’t this bad 50 years ago," McClean notes that many of the rivers were treated as drainage ditches at the time. So, bad water, no gnats; good water, lots of gnats.

“No good deed goes unpunished,” McLean said.

With all of the newfound attention on black flies, McLean doesn’t see the MMCD changing its name to the "Metropolitan Mosquito and Black Fly Control District."

“That would be hard to fit on a sign,” he said.

Community Editor

Mark Olson, the Chaska and Chanhassen community editor who has worked in Carver County for 20 years, makes any excuse to write about local history. In his spare time, Mark enjoys perusing old books, watching blockbusters and taking Midwest road trips.


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