Chattanooga may be in the middle of a yellow jacket outbreak, and Greg Allen drove all the way from Ohio just to take advantage of it.

“We call it an outbreak when the population explodes,” Mr. Allen said. “This happens every couple of years.”

A Portsmith, Ohio, resident who lived in Hixson during the mid-1990s, Mr. Allen said he came to Chattanooga on Sept. 1 and will stay through the end of October collecting, freezing and shipping yellow jackets to a Pennsylvania lab that produces antivenin for people who are allergic to their stings. He has come to Chattanooga because of an unusual decrease in the yellow jacket population in Ohio and an “outbreak” in Southeast Tennessee, he said.

“It’s crescendoing right now,” he said.

On Tuesday, Mr. Allen donned his special suit in a Hixson neighborhood and went to work. He put a jar at the top of a yellow jacket nest hole, wrapped a towel tightly around the opening and the mouth of the jar, then pounded the earth with a mallet. The wasps poured out of the ground, flowing into his jar like Jed Clampett’s bubbling Texas tea.

In about a minute, he had 1,000 angry yellow jackets in the jar.

Those that don’t get trapped let Mr. Allen know how angry they are: He estimated he’s been stung about 16,000 times in his 32 years of wasp wrangling.

There are more yellow jackets than usual in the area this summer, said Dr. John Skinner, professor of entomology at the University of Tennessee in Knoxville, but he stopped short of calling it an outbreak.

“I think that’s a bit severe,” he said.

Dr. Skinner attributed the larger brood of yellow jackets to several factors, including a mild winter and a rainy spring that produced a good apple crop, which meant lots of nectar-filled blossoms for food. Cold winters usually kill off most of the juvenile queens, which leaves only a few to start new colonies in the spring, he said.

“Obviously, if you’ve got more colonies started, you’re going to have more later,” he said.

Mr. Allen estimated that, in a normal year, about 3 percent of new queens survive the winter. This year, he said, it seemed more like 10 to 15 percent survived.

But the growth of the insects in Tennessee and the lull in Ohio may just be part of nature’s ebb and flow, according to Dr. Jason Oliver, research assistant professor of entomology at Tennessee State University.

“Any animal populations will fluctuate,” he said.

Still, the yellow jacket population should have decreased, Dr. Oliver said, because the drought over the last two years has cut down the amount of available nectar and other insects that the yellow jackets eat for food.

On the other hand, he noted, he has a nest in his yard for the first time in the seven years he has lived there.

For those pestered by the jackets, relief won’t be on the way for a couple of months, according to Dr. Skinner. The insects should be killed by the second hard freeze of the year, he said. But the first freeze of the year in Chattanooga usually occurs around Nov. 1, according to the National Weather Service.

By then, Mr. Allen will be back in Ohio, waiting for next year’s season. But while he’s here, don’t expect Mr. Allen, who described himself as a Civil War buff, to be out enjoying many local attractions or re-enactments.

Jacket-nabbing is a seven-day-a-week gig.

“I won’t have time for any of that,” he said.