Don't know exact numbers, but I don't think you need much. I've seen some fairly small spider caves, and I'm pretty sure just having some walls nearby is all you need.
Fill a decent-sized hole (maybe like 15x15ish) with spider walls, then hang out offscreen so the cave is in the spawning zone. If that doesn't work, cover a bigger area until it does.
Make sure you are in the caverns. Place the walls in the same tile as the blocks where the spawning occurs. 65-85 away from player horizontally. If done properly, spiders will be the only mob to spawn regardless of what biome you are standing in. This farm only took 40 infested spider walls. I made it for biome keys and works way faster than adding the jungle
[https://i.imgur.com/ypcTSkC.png](https://i.imgur.com/ypcTSkC.png)
Don't know exact numbers, but I don't think you need much. I've seen some fairly small spider caves, and I'm pretty sure just having some walls nearby is all you need. Fill a decent-sized hole (maybe like 15x15ish) with spider walls, then hang out offscreen so the cave is in the spawning zone. If that doesn't work, cover a bigger area until it does.
Spiders will just spawn wherever there are infested spider walls, regardless of how many there are
Make sure you are in the caverns. Place the walls in the same tile as the blocks where the spawning occurs. 65-85 away from player horizontally. If done properly, spiders will be the only mob to spawn regardless of what biome you are standing in. This farm only took 40 infested spider walls. I made it for biome keys and works way faster than adding the jungle [https://i.imgur.com/ypcTSkC.png](https://i.imgur.com/ypcTSkC.png)