Weather Extremes Could Cause Plague of Mosquitoes

2:55 PM, Apr 25, 2013   |    comments
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Dan McFeely, The Indianapolis Star

STORY HIGHLIGHTS:

Mosquito eggs are engineered to withstand the worst of Mother Nature and able to last for several years.

- The "super mosquito" (Psorophora ciliata) can grow 2-3 times the size of the usual pesky buggers and inflict real pain with a bite.

- These mosquitoes are not the kind - the Culex pipiens - that transmit the West Nile virus. 

Last year's drought that continues this year in some parts of the country was the most extensive in at least 25 years, destroying crops in the Midwest, causing water shortages in the South, and sending temperatures above 100 degrees in places where it broke records.

One might assume that one of the casualties of such a drought, which at its height in July affected more than 80 percent of the continental United States, would be mosquito eggs.

But, no. Mosquito eggs are marvels of nature, engineered to withstand the worst of Mother Nature and able to last for several years - until the drought ends and the rains come.

"They are incredibly complex; they have a plastron (protective surface) and actually have their own atmosphere," said Joe Conlon, an entomologist and technical adviser to the American Mosquito Control Association. "Hey, mosquitoes have been around at least 170 million years, and it's not because they are stupid."

The heavy rains have now come in a huge way, making it possible for those millions of mosquito eggs to begin hatching - and prompting some experts to warn of a huge plague of mosquitoes coming to a neighborhood near you.

Included in that warning: The ominous "super mosquito" (Psorophora ciliata) which can grow 2-3 times the size of the usual pesky buggers and inflict real pain with a bite, even through a shirt.

"Those are the 'gallinippers,' and they typically breed in marshes," said Ralph Williams, professor emeritus of entomology at Purdue University. "It is a large mosquito and an aggressive feeder."

Conlon agreed, describing them as having woolen legs and an inch-wide wing span. "There is actually an audible thud when they land on your back," he said.

Gallinippers are known to be floodwater mosquitoes, laying eggs in soil at the edges of ponds, streams and other water overflows when heavy rains fall, according to Phillip Kaufman, an entomology expert from the University of Florida.

"The eggs can remain dry and dormant for years, until high waters cause them to hatch," Kaufman said.

That's what some fear will happen soon in Indiana. But even if these super biters emerge in large numbers, they are not the state's dominant species.

Most Hoosiers are more likely to be swatting the smaller cousins, the Aedes vexans, which are pesky, but harmless by comparison.

Unless you're a dog, susceptible to heartworm.

"This has always been a problem in Indiana, but there is a simple fix," Williams said. "Pet owners should check with their vets and perhaps be put on preventive meds."

The severe storms, heavy rains and flooding that have pounded much of Indiana over the past week is what gave rise to this round of mosquito warnings.

"We got a lot of rain and this will translate into a larger than normal number of mosquitoes," said Williams. "We should start seeing them in the next few weeks."

These mosquitoes, experts say, are not the kind that transmit the West Nile virus. But if a dry spell hits, those potentially deadly mosquitoes - the Culex pipiens - could emerge in big numbers, too.

"If the rains stop and we get into a drier season, we will have a lot of places where standing water will hang out," said Williams, "and they like to hang out in tires, catch basins and any stagnant water that may be hanging around."

A spokesman for the Marion County Health Department said there has been no mosquito alarms sounded yet locally, but the department plans to monitor the situation.

Last year, local officials issued a warning that Marion County had so many discarded tires that the threat of West Nile was enhanced. Statewide last year, more than 60 people were sickened by West Nile, and six died.

Williams, who taught entomology for 35 years at Purdue University, said this year is not rare. He recalled the major West Nile outbreak of 2002 and heavy flooding in Southern Indiana several years ago.

And then there's the summer of 1975, "the worst year ever" when an outbreak of St. Louis encephalitis (transmitted by the same type of West Nile carriers) killed 50 and infected about 300 people.

"This always lingers as a potential problem," he said. "But nothing to panic about yet."

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