Minecraft wiki entry for Cave_spider_farming, associated text: Once the area around the cave spider spawner is all set up, you can start building your farm. Most farms have 2 basic components, the collector and the grinder. The collector is the area around the spawner, which collects the cave spiders, and moves them towards the grinder. The grinder is what kills the cave spiders. They are usually killed by either the player or an iron golem, because most sources of damage do not damage cave spiders.