CHICAGO – Mosquitoes have been eating summer Chi just like the rest of us.
The pesky little critters prefer temperatures between 50-95 degrees Fahrenheit with an average relative humidity of 42 percent or higher, according to a analysis from Climate Central, a non-profit news organization.
Chicago’s weather has fallen within these parameters almost every day in July, according to daily weather reports.
Historically, Chicago hasn’t been a hotbed for tiny bloodsuckers because the city’s long, terrible winter provides a “hard reset on the mosquito population,” said Shannon LaDeau, a senior researcher at the Cary Institute of Ecosystem Studies.
As temperatures warm globally and Chicago winters become milder, mosquito season is lengthening. Plus, the warmer weather actually allows the insects to reach adulthood sooner, which means they have more time to reproduce and their population increases faster.
“Because mosquitoes are ectotherms, everything about their physiology is temperature-dependent,” LaDeau said. “Warmer temperatures accelerate their growth and their replication of viruses.”
Mosquitoes appreciate our weather conditions and are becoming better adapted to urban life, LaDeau said. Chicago had 26 more “mosquito days” in 2022 than in 1979, according to the report showed.
“City mosquitoes are pretty much invasive species,” LaDeau said. “Mosquitoes that emerge from standing water in a tire left on the side of the road have become adept at surviving urban areas, giving them very close access to humans.”
Other areas, especially in the South, where temperatures often exceed 95 degrees, are seeing fewer mosquitoes because it’s too hot for them there today, LaDeau said.
“Even if the mosquitoes run up a wall where some areas are too hot for their physiology, the unfortunate truth is that the mosquitoes will adapt to that much faster than humans will,” LaDeau said.
For the most part, however, Chicago mosquitoes can be a relatively harmless nuisance Illinois sees occasional cases of West Nile Virus. The virus is spread when mosquitoes bite birds and pick up the virus, then bite humans, LaDeau said.
“Fortunately, it’s a very low-probability series of events because mosquitoes that come into contact with birds usually don’t come into contact with humans,” LaDeau said. “But if you have more time in the season for that to happen, and you have more mosquitoes around, then the likelihood of the disease spreading increases.”
One of the best ways to avoid mosquitoes is to make sure they don’t breed near your home, LaDeau said.
Mosquitoes are born in standing water, and it usually takes them about a week or two to reach adulthood, LaDeau said. If the water has predators – such as fish, frogs or other insects – the mosquito larvae won’t stand a chance.
“Anything that lives in water is far more effective at killing mosquitoes than anything you can do,” LaDeau said. “But most mosquitoes in the city come from stagnant water, which we don’t think of as standing water, like water collected in trash cans or gutters or tire swings or ephemeral water like puddles and rainwater.”
If you can’t remove the water, there are bacterial treatments you can use to kill mosquitoes, but that usually also kills their predators, LaDeau said.
“If you accidentally kill the other insects with these chemicals, as soon as it rains again, the mosquitoes will be back and there will be nothing else to control them, so you’ll have to keep treating the water,” LaDeau said .
Wearing long sleeves and applying insect repellent can help keep mosquitoes away in areas where you can’t control their presence, LaDeau said.
If you’re bitten and can’t stop itching, dermatologists can prescribe a topical steroid that can help heal the bite and prevent itching, said Dr. Parul Goyal, professor of dermatology at RUSH University Medical Center.
Hydrocortisone cream is a similar medication that helps with itching and can be taken over the counter, Goyal said.
People have found success in treating bites by placing pimples on bites because they can help “dry” the bite and provide a “physical barrier” that prevents you from scratching, Goyal said.
“It’s okay to leave mosquito bites alone and let them run their course, but it just depends on how bothered you are by them or how disruptive they are,” Goyal said.
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