David Scharf

Stingshot: Apis mellifera scutella, in your face

It was the third attack by Africanized honeybees—aka "killer bees"—in the gambling capital since October 1999, and just one of a rash of similar incidents across the West over the past year. On April 23, in Arizona's Saguaro National Park, a swarm of 10,000 chased four Dutch hikers, who managed to bolt to safety with only a few stings. Then on June 25, bees swarmed hikers in California's Joshua Tree National Park. The group endured 200 stings among them.

The bees, which were set loose in South America back in 1957 when a scientist unwittingly released some in Brazil, quickly worked their way through Central America, arriving in southern Texas about a decade ago. The insects advanced quickly through the Southwest in 1998, following a veritable interstate of flowers that El Niño rains paved through the states of Texas, New Mexico, Arizona, Nevada, and California. But those yummy blooms withered and died this past year under a La Niña–fueled drought—forcing the bees into populated areas in search of water and food.

"This year it's just swarm after swarm," says Dr. David Kellum, an entomologist with the San Diego County Department of Agriculture. Eric Erickson, director of the U.S. Department of Agriculture's Carl Hayden Bee Research Center in Tucson, predicts that within two years the bees will wing their way through central California's river valleys and into urban areas like San Francisco.

Still, don't stock your medicine cabinet with epinephrine just yet. The Department of Agriculture knows of only eight people—all elderly—who have died from killer bee attacks since the insects crossed the U.S. border."They're not out to hunt you down," says Erickson. "But any activity could set them off." —Michelle Pentz