They showed up in British Columbia in August, prompting a similar advisory from the Canadian province’s agriculture ministry.

The reputation of the mammoth hornets — which are distinguished by their yellow heads and can be nearly two inches long with a wingspan of up to three inches — precedes them.

May Berenbaum, the head of the entomology department at the University of Illinois at Urbana-Champaign, said on Monday that the hornets can wipe out an entire beehive. They’re generally not aggressive toward humans but their stingers are about six millimeters long and can inflict substantial pain and possibly even death in someone who is allergic, she said.

“You want to talk about beepocalypse,” Professor Berenbaum said. “They are sworn enemies of honey bees. I would say a bee’s worst nightmare. Probably the worst nightmare of a lot of people, too.”

A resident of Blaine, Wash., which is on the Canadian border and about 30 miles south of Vancouver, found a dead hornet on Dec. 8 that was then collected by state entomologists, the Washington State Department of Agriculture said. The agency said it confirmed that the specimen was an Asian giant hornet.