A heap of dead bees was supposed to become food for a newly captured praying mantis. Instead, the pile ended up revealing a previously unrecognized suspect in colony collapse disorder—a mysterious condition that for several years has been causing declines in U.S. honeybee populations, which are needed to pollinate many important crops. This new potential culprit is a bizarre—and potentially devastating—parasitic fly that has been taking over the bodies of honeybees (Apis mellifera) in Northern California.