Scouting for a Future Wasp War

Rick Vetter is desperately searching for yellow jackets.

He hunts Southern California’s foothills and flatlands, its urban and suburban neighborhoods. He scours theme parks, schools and zoos.

At a Riverside park, Vetter listened for the yellow jacket’s low buzz. He scooped a ball of raw chicken onto a plastic lid, set it on the ground and, within a minute, six of the stinging insects flew around the meat.

“Look, there’s a western yellow jacket, and that one over there is a German yellow jacket,” said a gleeful Vetter, an entomologist and research associate at UC Riverside, as he scouted the striped pests. “They like it here.”

But they’re not welcomed.

Vetter and fellow UCR entomologists are on a mission, funded by a three-year, $105,000 federal grant, to map their locations. After that, they’ll work toward reducing the yellow jacket population.

They are targeting two types of the yellow-and-black wasps.

The western species has long called Southern California home; nonnative German yellow jackets are proliferating in mostly urban structures, including classrooms and hospitals.

It’s necessary to distinguish between the two because they require different control methods.

The task has proved daunting. The team has been stung by state budget cuts, and this year the yellow jacket population is lower than usual.

However, winter rains may stoke a yellow jacket population boom, increasing the need to control them.

Besides being a nuisance, yellow jackets displace other insects and can scare people from campgrounds, amusement parks and other outdoor recreation areas.

More than 2 million people are allergic to stinging insects, according to the American Academy of Allergy, Asthma and Immunology in Wisconsin. Stings send about 500,000 people to hospital emergency rooms annually; an estimated 40 to 150 die.

“The more that people get stung, the greater the chance they will develop a potentially serious allergy to stings,” said David B.K. Golden, associate professor of medicine at Johns Hopkins University.

“The more insects, the more stings. The more stings, the more reactions. The more reactions, the more the danger and cost of insect sting allergy.”

Entomologists contend that the German yellow jacket, Vespula germanica, is of particular concern because it seems to prefer urban areas to the woodland nests of western yellow jackets, or Vespula pensylvanica.

The German species often lives in attics, cavities and wall voids. “They will not leave easily,” Vetter said.

The German wasps also tend to ignore heptyl butyrate, a chemical attractant used in traps that have worked to lure western yellow jackets.

The western yellow jacket is a lemon yellow, and the German is more of a “school bus” yellow, Vetter explained enthusiastically.

The western species has yellow rings encircling the eyes, Vetter said, and on the German wasps, the yellow is broken up around the eyes.

But that’s where his appreciation ends.

“My job is to kill them,” Vetter said. “If I really liked them, I wouldn’t be doing this.”

For information on how to help UCR entomologists map the yellow jacket population, go to https://wasps.ucr.edu/.