CHICAGO - First came the floods -- now the mosquitoes. An explosion of pesky insects is 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 that 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 downpours. 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."

In Lisbon, Iowa, about 20 miles east of flood-ravaged Cedar Rapids, biker Larry Crystal said mosquitoes have made his rides miserable.

"Every time I stop to rest at a rest area, these buggers just find a way to bite me all over my neck area between my helmet and jacket," he wrote on a bikers' blog.

"They seem to be very aggressive, they're even coming into my helmet, finding any bits of skin," Crystal told The Associated Press. "They're just going at it."

Some surveillance traps in Iowa have up to 20 times as many mosquitoes as 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.

In Iowa, the main culprit is the Aedes trivittatus, a common nuisance mosquito with "a voracious appetite, and they hurt when they feed on you," she said.

A relative called Aedes vexans is doing much of the biting in Chicago's suburbs, hit by recent heavy rains, said Mike Szyska of the Northwest Mosquito Abatement District.

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

Complaints and requests for insecticide spraying have the district "working day and night. We're extremely busy," he said.

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.