whereas those pupating amongst foliage tend to just get on with it, those with a subterranean tendency will require help. as soon as you see the larvae show the tall tail signs , (stop feeding, emptying of gut & wandering) then take the larvae from the cage and place in a deep plastic container filled about half way with sterile peat. ensure the substrate is not wet and not too dry, just damp . the larvae will wander on the surface for some time sometime digging itself in then out of the soil. eventually it will settle, disappear , and change into its pupal form