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Cooler weather is nice, but it’s not enough to end biting mosquitoes

It will take a frost or hard freeze to end our mosquito misery for the year. (Kevin Ambrose/The Washington Post)

The mosquitoes are still biting. If anything, they seem even worse these days: tenacious, like Japanese soldiers who don’t know World War II’s over and remain steadfastly loyal to a lost cause. That cause? Sucking my blood — and probably yours, too.

“Everybody is itchy these days,” said Mike Raupp. “It’s the season of the itch.”

I spoke with Raupp, professor emeritus of entomology at the University of Maryland, a day after he’d been down at the Navy Yard with his wife and 17-month-old grandson, sitting on a bench and trying to have a snack.

“We were battling — battling! — northern house mosquitoes and Asian tiger mosquitoes,” he said. “It was a free for all.”

What is up with these vicious dead-enders? Haven’t they had their fill? The calendar says summer is over. The mosquitoes haven’t gotten the memo. When will I be able to walk the dog and putter around the garden without dousing myself in DEET?

The short answer is: Not until our first frost, which typically comes before the first freeze. My friends at the Capital Weather Gang tell me that date averages anywhere from between Oct. 15 (for Dulles International Airport) to Nov. 19 (for Reagan National).

“Because they’re coldblooded, insect development is very closely tied to ambient temperature, so the warmer it is, the faster they develop,” Raupp said. “Our mosquitoes can have multiple generations every year. So as we move into a warming world — because it gets warm earlier, it stays warm later and it’s generally hotter — we simply have more generations of these mosquitoes every single year.”

To quote Bill Paxton in “Aliens”: “Well that’s great. That’s just [bad word] great, man!”

Said Raupp: “It’s the biological imperative for all living things to reproduce. They’re scrambling as fast as they can. This is what they do … They’re going to just crank out as many batches of eggs as they possibly can.”

To paraphrase the Richard Dreyfuss character in “Jaws”: The mosquito is really a miracle of evolution. It flies and bites and makes little baby mosquitoes, that’s all.

Brian Prendergast is sort of the Richard Dreyfuss of the mosquito hunt. He’s been battling mosquitoes professionally for 30 years. Prendergast is the Maryland Department of Agriculture’s mosquito control program manager, overseeing such countermeasures as spraying.

“The big nuisance is the Asian tiger mosquito,” Prendergast said.

While some mosquitoes bite at night, this nonnative species feeds during the day, “from an hour after sunup to an hour before sundown,” he said.

Like all mosquitoes, females lay their eggs in standing water. Asian tiger mosquitoes are good at exploiting man-made materials — old tires, plant pots, those ribbed gutter-extending hoses — and don’t fly far for a meal, typically less than 50 yards. If you’re being bitten by them, it’s probably because of water in your yard or a neighbor’s, Prendergast said.

Like Raupp, Prendergast marvels at the mosquito’s tenacity.

“That species will continue to take blood meals and lay eggs, what’s called the gonotrophic cycle,” he said. “They take a blood meal, lay eggs, take another, lay eggs, take another blood meal and lay eggs. They just keep doing that until something kills them. One of the things that might kill them is the cold weather.”

Another is my hand: Slap!

It’s an irony that at about the same time the weather is finally cool enough for us to put on long-sleeved sweaters and long pants — affording protection for our extremities — it’s too cold for the mosquitoes anyway.

There is a species that can overwinter by finding water below ground, in such human constructions as basements, tunnels, parking garages and subway stations. Culex pipiens molestus is known as the London Underground mosquito after one location it frequents. It’s also been found in the subterranean passages of the U.S. Capitol, Raupp said.

“They can breed underground in pools of water and bubble up at any point of time,” Raupp said.

Raupp said while our warm autumn days will leave us susceptible to mosquito bites, “when we're down in the 50s we can go out at nighttime and probably not get bitten.”

Before we hung up, Raupp shared one more bit of information about Asian tiger mosquitoes.

“You know why they bite on the lower legs?” he asked. “It turns out these mosquitoes actually are attracted to feet and ankles because we have a microbiome there in our stinky feet. They’re actually attracted to volatile chemicals released by bacteria on feet, in socks, in sneakers.”

“They’re kind of creepy.”

You won’t get any argument from me, Dr. Raupp.

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