The Amazing Patented Fail-Safe Fungology Cat Harvester™ is a device created by Earnaby Bladder. It is an incredibly complex machine, powered by steam and also souls. Cats are collected from neighbours and rounded up and so on, and are put onto a conveyor belt, which feeds them into the machine. Fungologists have been remarkably vague about why said cats are harvested, but no doubt it is for a very good reason.
On a completely unrelated note, soon after harvesting started, a highly profitable pâté business was started by Earnaby.