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Swat, smack, scratch!

The mosquitoes that survive a dry spell are itching to bite, say the experts.


© St. Petersburg Times, published June 28, 2000

The drought will soon be over. The mosquito drought, that is.

For weeks the Tampa Bay area has been blessedly free from mosquitoes. But rain has at last arrived, and with the rain come the pests.

"The first few weeks after a dry period are sometimes really rough," said Shelly Redovan, executive director of the Florida Mosquito Control Association. Area mosquito controllers said their traps and tests are still showing fewer insects than usual for this time of year. But that could change with the rains.

"There definitely will be an increase, but it's hard to say how much and when," said Mike Detert, field operations supervisor for Pinellas County Mosquito Control.

According to experts, heavy rainfall after a long dry spell can create the perfect conditions for an increase in mosquito populations.

Almost all mosquitoes lay their eggs in pools of water. When dry conditions hit, female mosquitoes lay fewer eggs and young mosquitoes are less likely to survive.

But when rain arrives, several factors can combine to cause more insects than usual. For one thing, salt marsh mosquito eggs, common to coastal areas, can survive dry weather unhatched. With rain, the accumulated eggs can all hatch at once, releasing thousands of young mosquitoes.

Freshwater mosquito populations also can surge after droughts because the insects tend to recover faster from dry conditions than their predators, such as dragonflies.

"It gives the prey time to get a jump on the predators," said Phil Lounibos, an ecologist and professor with the University of Florida's Medical Entomology Laboratory.

The mosquitoes that survive dry spells can be just itching to bite people. Lounibos said the insects avoid flying when the weather is dry, because the lack of humidity could dry out their wings. The mosquitoes then emerge from the storms hungry for a meal -- which means a lot of slapping and scratching for people.

"There may be adults out there waiting for a more humid environment as a cue to look for human blood," Lounibos said.

The good news in all this may be that mosquito-borne diseases are unlikely to rise, even if the overall bug population goes up. That's because only more mature mosquitoes carry St. Louis encephalitis, Florida's most common mosquito disease.

Encephalitis epidemics tend to strike in the late summer and early fall, when the mosquito that carries the disease has had several months to grow and mature. But the bug's late start this year will likely slow development.

"Ordinarily, by this time, they would have had time to build up. Right now, they've been virtually nonexist," Lounibos said.

Some of those who work outside all day have already noticed mosquito populations on the rise.

"I really didn't notice it all last year, but this year, in the last few weeks, it's been real bad," said Desmond Brooks, owner of Progreen Lawn care. He said he has been getting two to three bites every day since the rain returned.

Area mosquito control units continue to spray for both eggs and adult insects across the Tampa Bay area. The spraying goes on year-round but usually increases in the summer. For now, they say the area has had a relatively pest-free season.

"Usually at this time of year, we're getting hundreds of calls a day. Now we're hard-pressed to get 20," said Joel Jacobson, section manager for Hillsborough County Mosquito Control. "Unless someone can predict the weather, I can't predict the mosquitoes."

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