Tutorials/Cave spider farming

Cave spiders can be dangerous enemies - they are small: smaller than a slab, and apply the poison effect to the player. This makes them hard to farm. However, with some skills and care, it is possible. Cave spider farms yield lots of string and spider eyes without having to find a spider farm.

Before Farming
Firstly, find an abandoned mineshaft that contains a cave spider spawner. The spawner area can be recognized by tons of cobwebs. The cave spider spawner will be in the center of the cobwebs.

Once a spawner is found, there are few things that need to be done before starting the farm. First of all, get rid of all the cobwebs with a sword or shears (sword yields string) and light up the area around the spawner. However, do NOT accidentally mine the cave spider spawner, because you will not be able to get it back.

The next thing to do is layout the area. For the best results, make a square with 4 blocks in between the monster spawned and each wall, and 1 block between the spawner and both, the ceiling and the floor. You should now have a 9 x 9 x 3 area.

Spawning area
The spawning area is generally the same as for other monster spawner-based traps. However, remember that cave spiders are smaller - they can fit through gaps 1 block wide and 1/2 block tall. Also, remember that they can climb walls.

One way to get the cave spiders to go into the grinder is by pouring water on every block on one side of the spawning area. Then, dig down 1 for that whole side and place a water source block on each side of the ditch, and then signs over each block in the ditch. Now, all the water should eventually flow to one block. If you want to make sure that the cave spiders don't climb the walls, place water sources all along the top of each wall.

The block where all the water flows into should connect to the grinder room (make another channel if needed). Remember that you can stop the flow of water but still allow mobs and players to get through with signs.

Manual Grinder
Because of their size, ability to hold breath underwater, and ability to climb walls, lava, water, fall damage, and gravity grinders are ineffective or not as effective on caves spiders. Also, cactus isn't very effective, because cave spiders are small enough to go in between two cacti without taking damage (this is because cacti cannot be placed right next to each other). For this reason, it is very difficult to kill them automatically, without iron golems (see below). The easiest way to make a cave spider farm is to use a manual grinder.

Manual grinders require a hole that is too narrow for cave spiders but large enough to allow players to attack them easily. One simple way of making one is by placing two fence posts next to a closed door:

Automatic Grinder
One of the few ways to kill cave spiders without the player's aid is by placing iron golems in the collection chamber of the cave spiders. Place hoppers along the floor, all eventually connecting to a double chest. The iron golems will kill the cave spiders, and the loot will fall into the hoppers and go into the chest.

The disadvantage of using this method is that cave spiders will damage the iron golems as well, and eventually the iron golems will be killed. It is recommended to have an iron golem farm before trying to attempt this farm (otherwise, you will go through a lot of iron!).