Wisconsin residents often frequent lakes in the summertime. However, many quickly find they’re not the only regulars in these areas.
People find swarms of insects they refer to as gnats or lakeflies. In reality, you’re seeing a species of bug known as a midge, and despite their best efforts to annoy humans, they are completely harmless.
The midges Wisconsinites may see on their lakes or around places like the Memorial Union Terrace are called chironomids. There are several different types, but they are distinct for their transparent wings, long skinny legs, and their resemblance to mosquitoes.
Although midges look like mosquitoes, they don’t bite humans or bite anything at all. Dr. Dan Young, a professor of Entomology at UW Madison and the director of UW Insect Research Collection, explains how innocuous midges are.
“They look a lot like mosquitoes, and people probably are grossed out by them, and they’re running away from them and everything, but they don’t feed on blood,” Dr. Young said. “They don’t feed much at all as adults.”
Midges come from the water. Their larvae can be found at the bottom of bodies of water in the mud and sediment. They feed on the nutrients in the depths of the water before they grow and come to the surface.
Once they’re fully grown, they gain the ability to fly and leave the water. After midges are out of the water, they have one thing on their mind: reproducing.
Dr. Claudio Gratton, a professor of entomology at UW-Madison, explains that this is why we see so many hordes of midges near the water.
“The males create these swarms, and they are trying to find the females. So there’s this big fight as to who gets to be on the outside of the swarm,” Dr. Gratton said. “It means everything to pass your genes; that is the name of the game.”
Female midges then go back to the water to lay their eggs, and the cycle begins over again.
But why does it feel like midges are swarming around more than ever? Well, the answer is complicated.
Midge populations can vary heavily depending on the year, but once they actually emerge from the water, they only live for a couple of days.
“You’ll see them stagger at certain times of the year that they’ll be coming out, and they won’t be out for very long, but when they’re out, they’re just everywhere,” Dr. Young said.
So some years it’s just a matter of chance that midge swarms blow up. Additionally, Madison’s prominence of lakes, ponds, and rivers makes it a great place for aquatic insects to grow.
Furthermore, since Madison is a major city, these insects can end up in areas we may not expect them to be.
“We definitely have all the makings for some really, really good aquatic insect adult populations,” Dr. Young said. “Bounced against that, we’re a highly developed urban area, so once they come out as adults, their options are much fewer than if they were in a wild area.”
However, it’s possible climate change and human activity play a role in all of this.
Lakes that are polluted from agricultural runoff with nitrogen and phosphorus lead to algal blooms. Accompany that with warmer water, and algae is plentiful. This means that midge larvae have more food to eat
“So one of the things that you often see is more midges where waters are polluted,” Dr. Gratton said. “So when you get more nitrogen and phosphorus in the water, that generally fuels the lake to make more algae, and the things that eat the algae, at least in the sediment, are the midges.”
Before you grab a fly swatter and bug spray, it’s important to understand how beneficial midges are to the environment.
Midge larvae are a food source for bottom-dwelling lake fish, ducks, and wading birds. On land, spiders and insectivorous birds have a feeding frenzy on the midges. This all aids the lake ecosystem.
“There’s all this material and energy and nutrients that used to be in the bottom of the lake that now have been translocated and moved onto shore, Dr. Gratton said. “So it’s actually like the water, the ecosystem in the water is now feeding the ecosystem on land because the midges are moving this energy back and forth.”
