Invasive wasp swarms devouring birds, bugs in Hawaii

By Christine Dell’Amore, National Geographic News Attacking from nests as big as pickup-truck beds, invasive western yellowjacket wasps in Hawaii are munching their way through an “astonishing diversity” of creatures, from caterpillars to pheasants, a new study says. Adult yellowjackets consume only nectar. But they kill or scavenge prey to deliver needed protein to their growing broods. “They basically just carry it in their mandibles—you see them flying with their balls of meat,” said lead study author Erin Wilson, who just finished her Ph.D. at the University of California, San Diego. In their native habitat in the western U.S., the wasps die off in winter. But in Hawaii the wasps survive the winter, possibly due to mild year-round temperatures or subtle genetic changes. A longer life-span gives the insects more time to build up their nests. So what would normally be a basketball-size nest can become, at the extreme, several feet long—big enough to fill the back of a pickup truck, Wilson said. The extra room allows a colony of 50,000 workers to explode to 500,000 or more. Larger colonies mean that the insects deplete more prey than in areas where the wasps die off in winter. …