Swarms of Yellow Jackets Put Californians to Flight

Many Californians will remember this summer not for heat waves or pennant races but for the swarms of meat-eating yellow jackets that have declared a painful war on bare skin as far north up the Pacific Coast as British Columbia.

“Those suckers are eating us alive,” said Ruth Budesa of Sonora, a town in the Sierra Nevada foothills that has one of the worst infestations in what has become the worst summer for yellow jackets in memory.

Yellow jackets are a plague to late-summer picnickers every year in much of the West. But this year the wasps are driving loggers out of the forests, forcing campers to flee state parks and sending many more people to the hospital, some in serious condition. At least one horse has died after scaring up a nest of the wasps, sometimes called meat bees because of their appetite for flesh.

“This in my 10 years of experience is the worst I’ve ever seen for meat bees,” said Ed Heneveld, who treats sting victims in the emergency room at Tahoe Forest Hospital in Truckee. “I’ve treated five people myself who have been stung inside the mouth.”

More than 20 sting victims sought aid at the Yosemite medical clinic this weekend, including one person in severe shock, spokeswoman Mallory Smith said Monday. About 100 visitors have reported stings in the last three weeks, and park rangers are advising campers to avoid eating outside if they can help it.

Weather is one factor in the yellow jacket invasion. Mild winters allowed more queen yellow jackets to survive and set up new nests in the spring.

This time of year is also when the worker yellow jackets turn more assertive in their search for protein to stock the queen’s winter nest. The workers go after sandwiches, fish, soft drinks, hamburgers, even human skin--anything that resembles meat or sugar for the nest.

But entomologists also put some of the blame for the yellow jacket invasion on a new, more aggressive species of wasp from northern Europe. The Germanica variety swarms in much bigger colonies than the native California wasps. Instead of 150 to 300 worker wasps capable of stinging, a nest of the German intruders can have 5,000 to 6,000.

And they are more belligerent, say insect experts, although the yellow jacket is not one of the more friendly airborne insects even on his best days.

Initiation Disrupted

Last weekend some ornery yellow jackets disrupted the initiation of new “Clampers”--members of the fraternal group E Clampus Vitus--at Kennedy Meadows in the central Sierra Nevada. In one rite an egg was broken over the head of an inductee.

“They swarmed all over his head,” said Terry Barchus, an observer who escaped with one sting on his arm. “He had to be washed off real fast. Luckily he wasn’t stung.”

Fighting back is not advisable, say those with experience.

“As soon as you slap at a yellow jacket they immediately sting,” said Glenn Bissell, who has fought a losing battle against the wasps for nine years for the El Dorado County Health Department. “You have to brush them off slowly.”

Last year, which was the worst of the 1980s before now, Bissell caught about five or six wasps a week in each trap he set out in the Lake Tahoe area. Now he is catching more than 50 a week in each trap, some of them the German variety.

‘Phenomenal Number’

“We’re seeing just a phenomenal number of yellow jackets,” Bissell said. “The beaches are just humming with them right now.”

Earlier this month, Janice Carmen was riding horses at Clark’s Fork, east of Sonora in the Emigrant Wilderness, when the two lead horses walked over a nest and scared up a cloud of wasps. The third horse, a 14-year-old gelding named Cody, was stung severely on the legs and haunches. Carmen, riding on the fourth mount, managed to help gather the horses and get them away without being stung herself.

Cody was surrounded by a second swarm and stung again before the group made it back to camp. The animal went into shock, Carmen said, and died soon after despite a veterinarian’s care.

“The best thing you can do is find where they go in the ground at night, pour motor oil into the burrow and light it,” Carmen said.

All yellow jackets make pests of themselves in about the same way. They hover around food and sweet drinks and, when they land, will try to grab pieces of food with their mandibles. The mandibles can also be used to bite humans, but it is the stinger that contains the venom. Unlike honey bees, which typically sting once and leave their stinger, yellow jackets can sting repeatedly.

Sting Can Be Deadly

“One sting is enough to kill a hyper-sensitive human,” said George Poinar, an entomologist at UC Berkeley. “Fifty to 75 stings are enough to kill a normal human.”

California officials are unable to recall any fatalities blamed for certain on yellow jackets. However, Roger Akre, an entomologist at the University of Washington who wrote the landmark book on yellow jackets, said that more than 500 people a year in the United States may die of sting reactions that are attributed to heart attacks or other ailments.

Loggers and other forest workers are being hit harder than tourists this year. Trucks and tractors on the forest floor disturb the nests, then the wasps swarm and drive the operators and loggers for cover.

Loggers Refusing to Work

In some areas, loggers have been refusing to work, said Dan Ward of the Sonora office of the California Department of Forestry. “As soon as you get out of the truck you have them buzzing around your head,” he said. “If you come near their nest they come out with a vengeance.”

The good news, say the insect experts, is that the wasps should begin to die off as soon as the weather turns cool. “This is probably the last big month,” Poinar said.

NASTY SUMMER VISITOR

Yellow jackets, wasps of the genus Vespula, are most active in late summer. Found in most of the West, they sometimes build hives in attics or under eaves, but the most threatening species to humans nest in the ground. This time of year they are drawn to many kinds of foods--meat, fish and sweet things such as soft drinks and candy--seeking protein to store in the nest for winter. Yellow jackets sting when provoked and, unlike honey bees, can sting repeatedly. They also have mandibles used to grab meat and, sometimes, to bite humans. Sting victims should seek immediate medical help if they feel any difficulty breathing, a lump in the throat or chest pain.