Joybugs are insects from Mongo with a fatal bite. A joybug bites Nick Gilmore in , endangering his life. Joybug infection is called "the happy death" on Mongo, because it secretes a venom that makes the victim experience complete euphoria before dying. To keep a victim alive, his caretakers have to keep him from experiencing any happiness. The children of Mongo have a nursery rhyme: "When bit by the bug, all joy will destroy. But cause pain and sorrow, they may see tomorrow. When bit by the bug, only strife will save life."