More mosquitoes right now? We've got bad news and good news.

  • The common floodwater mosquito, the aedes vexans, being counted at the Northwest Mosquito Abatement District.

    The common floodwater mosquito, the aedes vexans, being counted at the Northwest Mosquito Abatement District. Daily Herald File Photo

Updated 9/20/2018 9:27 AM

Mosquitoes are really bugging us, even if experts say they're out in pretty typical numbers.

Trap-count data in DuPage County and other areas "is generally what we would expect to see from the extended period of high temperatures and excessive rainfall over the Labor Day weekend," said Laura McGowan, spokesman for Clarke Environmental of St. Charles.

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"Our numbers are below normal right now," said Michael Szyska, director of the Northwest Mosquito Abatement District based in Wheeling. There has, however, been "a little increase" in the past week.

Here's what you should know.

Why mosquitoes?

Late August and September is peak mosquito season.

"We've had 12 nice, warm days," McGowan said, and some moisture, which is necessary for hatching eggs and larval development.

Aedes vexans mosquitoes, aka floodwater mosquitoes, are aggressive biters. It is right in their name: "vexans" comes from the Latin word "vexaré," meaning to harass, torment or tease. It's the females biting: They need the protein from blood to produce eggs.

The other mosquito prevalent here are culex varieties, mostly culex pipiens. They transmit West Nile virus.

Why spray?

Besides causing itching, mosquitoes carry diseases, including ones that cause encephalitis in humans and animals, and heartworm in dogs.


Spraying adulticidal chemicals through the air is a measure of last resort. It kills flying mosquitoes. Clarke sprays mist about 30 feet in the air from a slow-moving truck. Szyska said the oil-based spray he uses can travel as much as 300 feet from the truck, provided it doesn't encounter foliage or buildings. "Once it settles (on an object) it breaks down very quickly" and becomes ineffective, McGowan said.

When will they go bye-bye?

Mosquitoes slow down around 60 degrees Fahrenheit. Some culex mosquitoes can survive by hibernating in wet places not subject to freezing, such as storm sewers. The aedes vexans adults are killed by a hard frost, which is when temperatures fall to 28 degrees or lower. The median hard frost date in this area is between Oct. 11 and Oct. 20, according to the state climatologist office.

At that temperature, "they're goners," Szyska said. "They're dead."

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