If you're scratching more than normal, there's probably a simple explanation: an invasion of salt marsh mosquitoes.

These pests, hatched on a recent wave of high tides along the Gulf Coast beaches, are now moving inland and making their presence felt as they search for new, unsuspecting blood donors in parts of Harris and Fort Bend counties.

Fort Bend County's mosquito control chief, Weldon Sheard, said he's being bombarded with calls from distraught homeowners about "every 20 seconds," especially in the Sienna Plantation and Mission Bend areas.

Harris County also is being inundated with mosquito swarms around Friendswood on the southeast side.

During such outbreaks, the hardy salt marsh mosquito can fly for miles in quest of a blood meal when pickings are in short supply at home. They are very aggressive, and can snack 24 hours a day, experts say.

So as far as being an itchy, irritating nuisance - it's the worst of breeds.

But it does not transmit lethal viruses, such as West Nile, as the more reclusive culex variety. The culex, on the other hand, is less likely to take a vampirish bite because it bites just before darkness or light. They also don't stray far from home like the salt-marsh breed does, said Brazoria County's mosquito control director Jim Ryan.

More Information Salt marsh mosquitoes 1 Hungry all the time: Considered aggressive biters 1 Monster migrators: Can travel up to 40 miles for a meal and have a flight range of more than 100 miles. 1Strong fliers: 15 mph winds do not deter them. 1The city lure: Attracted to city and industrial lights. 1 Color: From very dark black to dusky brown, with a grey patch on the sides; look for white ring or rings around proboscis and several around legs. Sources: Jefferson County, American Mosquito Control Association; Loyola University, Rutgers University

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During recent drought conditions, a couple of year's worth of salt marsh mosquito eggs were lying dormant along the beaches, waiting for the next high tide. The ground must flood before the eggs can hatch into an aquatic larva that matures into a winged adult in about five to eight days, said Galveston County's mosquito director John Marshall.

Winds elevate tide

The National Weather Service said a persistent southeast wind caused the tides to elevate about a foot above normal, washing 2½ feet past the barnacle line on the beaches for 10 days just before Labor Day.

At that point, the conditions were perfect and the mosquito population exploded.

"I noticed a whopper of a mosquito problem myself but then it started dropping Monday," said meteorologist, Kent Prochazka, who lives in Brazoria County.

That's because famished swarms looking for greener pastures had moved inland on the winds and are now assaulting residents in Harris and Fort Bend Counties.

Nadia Khalil, who drives a school bus in the Sugar Land area, said mosquitoes are attacking students waiting to climb onto her school bus each morning and then the insects come on board with them.

"They are biting the children and me," she said. "I'm strapped with a seat belt driving 40 to 50 miles per hour. I can't do anything."

And at her neighborhood watch group this past weekend, the mosquitoes were hungry. "Nobody could take it. All anybody could do was itch," she said.

'30 at a time'

Clifford Sanford, who has been partially paralyzed since a diving accident when he was a teenager, said he's never seen an outbreak this bad in Fresno. He feels particularly helpless when he tries to maneuver in a motorized wheelchair between a van and his home.

"They swarm all over me, 30 at a time," he said.

Mosquito control organizations are sending trucks out to spray almost nightly, looking for both the brown and black salt march species. The three coastal counties are also spraying from planes.

Luckily, adult mosquitoes don't have a long life expectancy in the wild, usually only about a month, experts say. But they are still survivors.

"My wife gave me a piece of prehistoric amber with a mosquito in it. Dinosaurs never stood a chance with them," said Ryan of Brazoria County. "What do you think we can do?"