Minecraft wiki entry for Cave_spider_farming, associated text: Another way is to make a 9x9 plus 4 air blocks under the spawner and one on it. On the floor put magma, and in the upper corners, water. It will push the spiders in the middle. Under the magma block put minecart hopper, and under it a normal hopper which leads to a chest. The storage is expandable. The only thing you have to do is stay at the level of the spawner, right next to the farm.