Biologists at UC San Diego have discovered that a tiny single-celled parasite may have a greater-than expected impact on honey bee colonies, which have been undergoing mysterious declines worldwide for the past decade. In this week’s issue of the journal PLOS ONE, the scientists report that a microsporidian called Nosema ceranae, which has been known to infect adult Asiatic and European honey bees, can also infect honeybee larvae.