CHICAGO — First came the floods, now the mosquitoes. An explosion of pesky insects are pestering cleanup crews and just about anyone venturing outside in the waterlogged Midwest.

In some parts of Iowa there are 20 times the normal number, and in Chicago up to five times more than usual.

The good news is these are mostly floodwater mosquitoes, not the kind that usually carry West Nile virus and other diseases. But they are very hungry, and sometimes attack in swarms with a stinging bite.

Heavy rain followed by high temperatures creates ideal conditions for these bugs, whose eggs hatch in the soil after heavy rains. Scientists call them nuisance mosquitoes. You could call that an understatement.

“About 3 p.m. the bugs come out pretty bad. They’re all over the place,” Bill Driscoll, a flood cleanup worker in Palo, Iowa, said this week. “We’ve been burning through the repellent with the volunteers.”

Some mosquito surveillance traps in Iowa have up to 20 times more mosquitoes than in recent years, said Lyric Bartholomay, an Iowa State University insect expert.

For example, last week, 3,674 mosquitoes were counted in Ames-area traps, compared with 182 for the same week last year, Bartholomay said Wednesday. Trap quantities are just a tiny snapshot of the true numbers of mosquitoes flying around.

Mosquito numbers in northwestern suburbs peaked last week at about five times higher than normal for this time of year, said Mike Szyska of the Northwest Mosquito Abatement District.

Right now there’s no evidence of higher than normal numbers of Culex mosquitoes, more commonly associated with West Nile virus. Several states have found evidence of West Nile, but only a few cases, which tend to start occurring later in July.

But health authorities say that could change with drier weather, which Culex mosquitoes prefer, so they’re advising people to take precautions.

Culex mosquitoes breed in stagnant water and sludge in protected areas including ditches, storm drains or backyard bird baths and discarded tires, Szyska said.

In the meantime, the explosion of floodwater mosquitoes has left many people feeling like mosquito magnets. And about 10 percent of the population actually qualifies, according to entomologist Jerry Butler, a professor emeritus at the University of Florida.

These are the people who get covered in bites while their porch partners or biking buddies are left unscathed. Many of them get exaggerated skin reactions to the bugs — hard red welts or hives that can itch for days.

Mosquito magnets

Want to avoid attracting mosquitoes? Entomologist Jerry Butler says the bloodsuckers zero in on:

n Sweat and carbon dioxide;

n Those who have consumed alcohol;

n Alcohol in lotions and perfumes;

n People with high cholesterol.