A form of self-destructive hysteria that overcomes the Grasshopper-kinden of the Northern Steppe on a periodic basis. An old Grasshopper woman describes it best in The Price of Salt:
"There are many kinden on the steppes," the old woman told them, forcing the words out. "Cicada, Dragonfly, Roach-kinden, but most of all there are my people. We have many tribes. We roam the steppe in our thousands, in our tens of thousands, increasing and increasing, many and many, until there are too many. Then the full moon will be a grand moon. Then the Locust Madness comes, and we run mad and destroy all we have, and we kill and kill," her withered hands made jabbing motions at each other, "and we die and die. We dash ourselves against stones. We drive ourselves onto our neighbours' blades. We fight and dance and run until we starve or drop from weariness. Until at the last there are no longer too many of us, and the Locust time is passed, until it comes again. Perhaps tomorrow, perhaps the night after, perhaps in a tenday, who can say?"