When James Barron went into his smokehouse in southern Alabama to grab an ax, he was alarmed to see a giant wasp nest about seven feet wide extending along the wall. It had been two months since he had last set foot inside.

“You don’t think about looking at the roof,” Mr. Barron said. “It’s just now really showed up, and it’s gigantic.”

Mr. Barron immediately retreated, and later sprayed hornet killer on the nest with his son. He said that just angered the yellow jackets , the highly aggressive wasps that live in such colonies. Mr. Barron was stung 11 times.