As a recent transplant to Talkeetna, I was shocked and annoyed by the swarms of mosquitoes here. So, I called up entomologist Derek Sikes at the University of Alaska Fairbanks to learn more.
Turns out there’s a lot to learn about mosquitoes.
“Mosquitoes could be considered to be these very fancy machines for turning blood into more mosquitoes.”
The purpose of mosquitoes is to make more mosquitoes. And they’re really good at it.
Sikes explains that there are 30 species of mosquitoes in Alaska. However, in interior Alaska, there are 20, and in any one place, you won’t see more than ten. Most Alaskan species here in the summer are in the genus Aedes.
“They are faster flying, much more numerous, far quicker to bite.”
They winter as eggs in water. The eggs hatch in the spring, the larvae feed in the water, pupate, and emerge as adults in May.
Mosquitoes emerge and have two things in mind. They want to mate, then feed. All mosquitoes that drink blood are female. Males, alternatively, feed off nectar.
“But the females only get the blood to make eggs, in order to provide food for their offspring.”
Carbon dioxide stimulates the female to start host-seeking. They buzz around our heads because that’s where we expel the most CO2. All summer they’re busy biting…
“And then are really annoying, until about, once we start getting below freezing temperatures at nighttime, which happens sometime in September usually, then the mosquitoes start disappearing.”
This explains why the end of most Alaskan summers are mosquito free.
Sikes says that mosquito species are shifting.
“This one that’s moving north, this is the species Culex tarsalis. It’s moving north probably because of warming temperatures. And so we do expect, globally, species to expand their ranges northward, and so we could start seeing disease transmission in areas that don’t have it right now.”
Culex tarsalis transmits diseases like Norovirus. Sikes would not be surprised if by the end of this century, it became thoroughly established in the north, in places like Alaska.
Warming trends in the long term may also lead to a decrease in mosquito populations. Sikes says that permafrost in Northern Alaska is shrinking. Permafrost keeps water from evaporating and helps maintain breeding ground.
“Permafrost is thawing, and that means that there is going to be less standing water, and that will probably affect the mosquito populations. I mean, if we fast-forward 200 years, 300 years in the future and there’s no permafrost in Alaska, I imagine there will be a lot fewer mosquitoes.”
I asked Sikes what makes a good mosquito year.
“Mosquito populations go up and down every year. We don’t have a very good understanding of what drives those increases and decreases, but there are some sort of obvious variables that are predictors like moisture, because the larvae are aquatic.”
Mosquitoes can breed in surprisingly small amounts of water. There are mosquitoes that can breed in containers—flower pots, vases, and cups.
There are four big factors that affect a mosquito year:
“Water, temperature, predators and competitors.”
A “bad” year of mosquitoes occurs when all these variables are lined up in favor of the mosquitoes.
“Low predators, low competitors, good temperatures, adequate water.”
Sikes explains that though entomologists know the larvae need water to lay eggs, they haven’t been able to find strong patterns between rainfall and mosquito abundance. There is the general rule that a wetter year leads to more mosquitoes, but there are exceptions.
“Mosquito abundance can be higher after a drought year.”
A recent study found that drought will empty out a lot of temporary water bodies, killing other insects—all other predators and competitors.
“The year following, when the rain fills up those water bodies, the mosquitoes are able to colonize them and breed in a mostly predator-free environment. So their populations can get huge.”
With the drought this summer, this doesn’t bode favorably for next year’s mosquito season.
Sikes says that this is why spraying for mosquitoes isn’t a good idea. It’s similar to the “drought-year” effect. It kills all their competitors and predators.
I asked Sikes about a mosquito-specific insecticide. What if we could get rid of just mosquitoes? Sikes indicates that it probably wouldn’t be a major problem if they completely disappeared.
“Mosquitoes transmit so many diseases among wildlife, and drink so much blood that if they were to somehow go extinct, it would probably be for the net benefit of humanity, even if there were some small ecological consequences.”
Humans can control the environment to a certain degree. In fact, Malaria, which is transmitted by mosquitoes, used to occur on the eastern seaboard of the United States.
“We drained swamps, we dried wetlands, we used insecticides, we did a lot of things and eventually got rid of the disease.”
Sadly, it would be nearly impossible to wipe all species of mosquitoes from the face of the earth. So, for now, we’ll all just have to keep our skin covered and try our best to ignore the buzzing in our ears.
For KTNA, I’m Nell Salzman.
