SAN FRANCISCO — Swarms of stinging insects have etymologists from South Lake Tahoe to San Francisco fielding calls from besieged property owners, perplexed government officials and even homicide investigators asking how to keep the bugs away from dead bodies.
Warm, dry weather in Northern California has produced a bumper crop of flying pests this summer, The San Francisco Chronicle reported Sunday. The infestation at outdoor dining spots and crime scenes has included run-of-the-mill Western yellow jackets, but officials also are reporting an increase in European paper wasps, a species that arrived in California about two decades ago.
“What happens now in late summer and fall is you have the largest density in the nest, so they are all foraging for sugar and carbohydrates,” Andrew Sutherland, the San Francisco Bay Area pest management adviser for the University of California cooperative, said. “The search for sugar changes their behavior a little bit so they are more likely to come in contact with humans.”
The foreign wasps are bigger than their American cousins, but generally less aggressive, said Lynn Kimsey, a professor of entomology and director of the Bohart Museum of entomology at UC Davis. They also are more likely to build their nests under eaves or other places where they are likely to encounter people and wield their stingers in defense, Kimsey said.
“Two things are going on: You’ve got this introduced species that’s going through a population explosion and you have a really mild spring, which allows more wasps in general to survive,” Kimsey said. “It’s good for them, bad for us. It also explains why cold winters are good. There are certain things you want to kill off during the winter.”
El Dorado County environmental health specialist Karen Bender tells the Chronicle that her department is getting about 10 complaints a day and removed 345 wasp nets last month, 50 percent more than during the previous August.
“We expect the trend to continue through the month of September,” Bender said. “I’ve been to several picnics lately, and they just come out swarming.”