Metro blackflies poised to bite

First came the floods.

Now comes the pestilence.

Black flies, the nasty biters that can ruin a picnic even faster than mosquitoes, are about to appear in force in the metro, just in time for the run-up to Independence Day camping and parties.

Also known as biting gnats or buffalo gnats, the flies breed in running water, and the recent flooding rains have left parts of Minnesota awash in high, running water.

Smaller and stouter than mosquitoes, the flies don't bite with the same pinpoint finesse because they have "more slashing mouth parts," said University of Minnesota Extension entomologist Jeff Hahn. The flies essentially rip off a piece of their prey's skin so they can draw blood, which they use, like mosquitoes, to provide nutrients to help them produce eggs. The flies also inject an anticoagulant into the wound, so for the victim it's ouch, then itch.

"Most people would rather be bitten by a mosquito," Hahn said.

Several species don't bite humans, preferring to simply hover around the highest point on people's bodies. So if you're lucky they may just drive you crazy instead of biting you.

There's been so much excess water that the bacteria mosquito control workers pour into rivers to kill the flies are being diluted into uselessness.

"The amount we'd need [to be effective] is so great, we'd blow the whole budget in one treatment," McLean said.

High river flows in some areas have prevented workers from getting out in boats to distribute the insecticide anyway, he said.

What's more, the agency doesn't really know how bad the black fly outbreak will get because some of the tracking devices it attaches to buoys have been swept away by the floods.

Black flies were so thick in northern Minnesota earlier this spring that nesting loons were forced into dives to shake off blankets of them. Some of the birds simply abandoned their nests, leaving eggs exposed to heat, cold and predators.

It's too soon to say how many loon chicks died. But the losses to the population of Minnesota's state bird could be eased because loons can lay a second round of eggs in a season, added Carrol Henderson, DNR nongame wildlife program supervisor. While those eggs will hatch in coming weeks, the chicks will need two months to learn to fly, leaving them less time to develop before the fall migration, Henderson added.

The loon-pestering species of black fly prefers waterfowl blood over human blood. That may be one reason campers in the Boundary Waters haven't been reporting being bothered any more than usual.

"Quite frankly, I think the weather has been the problem for us, more than the bugs," said Cindy Hansen, co-owner of Sawbill Canoe Outfitters near Tofte.

As floodwaters recede, the black fly problem should improve.

But persistently high levels of standing water could — you guessed it — lead to fresh problems with mosquitoes. Still water is good for late-season species that carry disease, McLean said.