Despite friendly skies and perfect temperatures, a recent family trip to the Boundary Waters Canoe Area quickly became a reprise of “There Will Be Blood.” Sure, you expect some mosquitoes on the portages, and you anticipate that every evening around dusk a high-pitched hum will rise from the forest, a warning to campers that they must duck into their tent or face exsanguination. Or worse.
But this year it was much more than that, mirroring what I had experienced earlier in the summer on Lake Winnibigoshish. Daytime mosquito levels seemed to rival portage or dusk levels; the casual lunches, the blueberry picking, the afternoon swims capped off by drying in the sun on a slab of Canadian shield granite — all of these typical pleasantries were interrupted by packs of little welts-on-wings. Paddling out into the lake could provide some refuge, but not until you killed off the bevy that followed you out there like Pig Pen’s cloud.
I asked David Neitzel, a tick and mosquito expert at the Minnesota Department of Health, the obvious question: “Is this plague of mosquitoes a sign of the End Times?”
“No,” Neitzel reassured me. “What it is is a sign of is an extremely good snowmelt — we had a lot of snow, so we had a lot of water inputs coming into the spring — and since then we’ve had a lot of wetness on top of that across most of the state,” he explained. According to Neitzel, these snowmelt pools will typically dry up as the frost goes out of the ground, but it’s enough to produce some of the first mosquitoes of the year.
Snowmelt? Aren’t mosquitoes a warm weather, almost tropical kind of insect? How warm would a snowmelt puddle have to get to breed mosquitoes?
Several weeks to develop in cold pools
“You’ll find mosquito larvae in pools that sometimes still have a little bit of ice in them,” Neitzel explained. “But the speed of mosquito development is very much temperature dependent, even for these mosquitoes that have adapted to our temperate climate. That first batch of mosquitoes takes a long time, several weeks, to develop in that relatively cold water,” Neitzel continued, “whereas right now, mosquitoes that are developing out in the wilds of Minnesota, they take a week, week-and-a-half tops before they’re out of the water.”
So how’d it get this bad?
“What we had this spring was a whole bunch of snowmelt pools, which led to a whole bunch of snowmelt pool-exploiting mosquito species — mainly in the genus Aedes, which are some of the main mammal-feeding mosquitoes that we have here in Minnesota,” chronicled Neitzel. “And then the spring was really wet, with all sorts of rain storms, pretty frequent and actually spaced just right, so that every time we had a batch of our early summer pest mosquitoes coming out, they had a chance to lay their eggs.”
We tend to think of mosquitoes as all one thing, but according to Neitzel, there are roughly 51 species here in the state, about half of which feed on humans. Some fill a certain niche, early spring for example, so that a dry spring knocks them out of the competition altogether. Other species like Aedes vexans, our state’s major ear-buzzer, fill a broader niche. “They’ll keep on going to September here as along as they have regular moisture inputs, enough to flood the eggs, like a good thunderstorm.”
So moisture (and blood) are key ingredients in the mosquito life cycle, but it’s also critical to their physical being, as their pestilent, wretched little bodies can dry out easily.
“Mosquitoes need to be kind of careful to not be out in hot, dry or windy conditions for too long, because they will lose enough moisture and just desiccate — and then they’re done,” Neitzel explained.
Still buzzing in, even in the wind
The need to keep from drying out tends to keep mosquitoes back in the woods during the daytime, particularly if it’s windy. But that didn’t seem to be the case this year: We camped on some minimal-vegetation solid-rock campsites with a wind coming off the lake, and even so, they were still buzzing in and dragging the younger children off into the bush.
“It is the sign of the End Times!” I again pleaded with Neitzel. “A super-mutant mosquito species has developed that doesn’t dry out in daytime conditions! We’re all going to die — or get really itchy and run out of Benadryl cream.”
He balked at the idea, but was sympathetic to our plight. “There’s a lot of mosquito biomass out there, it’s pretty impressive,” he replied calmly. “They can exploit moisture conditions when the conditions are good, and even when conditions are not good, there’s enough of them out there that they can maintain their populations.” And this summer’s cooler temps have only helped their cause.
Is there a way to quantify the biomass? How do we quantify what a record mosquito year is?
According to Neitzel, the only quantification going on is in the seven-country metro, where the Metropolitan Mosquito Control District (MMCD) uses CO2-baited traps to make weekly counts.
Per Sandy Brogren, an entomologist with the MMCD, the peak number of mosquitoes captured so far this year was the week of June 16. Comparing June data from the past 10 years, Brogren noted that there were two other years with higher peaks, 2004 and 2005—not bad considering we had the second-wettest June in history this year. Of course, that’s in the metro, and Brogren echoed Neitzel’s comments about this year’s heavy snowmelt up north, noting that adult mosquitoes can live for three months or more.
It’s strange to think that our snowy winter is, in some very aggravating and itchy ways, still with us.