NORFOLK, Va. - Fire ants are showing up in greater numbers in coastal Virginia, much to the alarm of gardeners and farmers who dare disturb their nests.

"The way they bite, you would think they were the size of an alligator ... " said Carl Lohafer, a Virginia Beach resident who discovered colonies in his yard two years ago. "It was like a hot poker jabbing you."

In Virginia and elsewhere, the ants appear to thrive in the favorable climate of the coastal region.

Infestations of the ants have been reported in greater numbers since 2000 than in all of the 1990s, according to Virginia's Department of Agriculture and Consumer Services, Office of Plant and Pest Services.

Seventy-eight infestations were confirmed in South Hampton Roads between 1990 and 1999, compared with 124 detected between 2000 and the first part of 2006.

Of the 318 cases of infestation in Virginia, 64 percent have been in South Hampton Roads, according to state records.

The ants also have been discovered in Accomack, Chesterfield, Henrico, York, Isle of Wight, Gloucester and James City counties, and the cities of Hampton, Newport News, Richmond, Williamsburg and Franklin.

The number of Virginia infestation cases has increased because of dry weather conditions that interfered with the treatment process. The chemical used to combat the pests, Dursban, also was phased out and a less effective treatment was introduced.

Another major factor has been an increase in the building of homes, subdivisions and malls, which require the importation of soil, mulch, plants, sod and other products that can be infested by the ants.

Imported fire ants were brought inadvertently by ship to the United States from South America in the 1930s, according to the U.S. Department of Agriculture.

In many Southern states, but not Virginia, quarantines are in place to regulate the movement of plants, soil, mulch and other lawn and garden products to ensure shipments do not harbor the ants. The shipments of the articles outside of quarantined areas require inspection and treatment.

The ants are known for their aggressive behavior and venom-packed sting

"If you get them in your backyard, you can't go out and have a picnic," said Frank Fulgham, program manager for the Office of Plant and Pest Services. "And with kids, they can't play out in the yard."

The ants are highly sensitive to disturbances of their mounds and react with swarming, relentless attacks. Some people are allergic to the bites, which typically leave blistering but are rarely life-threatening to humans.

"In the South, they will kill animals," Fulgham told The Virginian-Pilot. "It could be a cow or a dog, if it's something that can't get away from them."

Experts believe the ants will reach a northern point where the winter weather will stop their progress, perhaps Richmond or northern Virginia.

For now, however, they're making their mark in southeastern Virginia.

"We've found them on the Virginia Beach Boardwalk before, so they can pop up anywhere," said Fulgham, who urges residents to contact his agency whenever the ants are detected.