In June 2013, a pesticide application on ornamental trees in a shopping-center parking lot in Wilsonville, Oregon, led to the largest documented mass fatality of bumble bees in North America. A new analysis of the incident estimates more than 100,000 bees—primarily Vosnesensky bumble bees (Bombus vosnesenskii)—from nearly 600 colonies were killed, which researchers cite as a cautionary tale about the dangers of pesticides to native bee populations. (Photo courtesy of James P. Strange, Ph.D.)