Minecraft wiki entry for Cave_spider_farming, associated text: Cave spiders can be dangerous enemies - they are shorter than a slab, one block wide, and apply the poison effect to the player. This makes them hard to farm. However, with some skills and care, it is possible. Cave spiders drop the same things that spiders do (string and spider eyes). Despite this, cave spider farms are useful because their spawners are easier to find. While a spider spawner may be tucked away in some dungeon, cave spider spawners can be found in many mineshafts.