Today I will be explaining my spider jockey farm that I have made.
I made this farm to obtain rare spider jockeys that have jack o lanterns on their heads. But I never used it on our server because it depends on the mob cap to spawn in mobs.
This farm is similar to my simple spider farm by having spawning floors that have 1m tall of air with a transparent block above it. This allows only spiders to spawn in that area. For every spider that spawns into the game there is a 1% chance that the spider will be a spider jockey. The jockey is a skeleton.
By having a farm that only spawns spiders the chance of a spider jockey to spawn increase because no other mobs will spawn besides them. When the spiders spawn they will be flushed out of the spawning floors with water. Then they will fall down into holding bay and from there they will be pulled out by minecart one at a time. Once in the minecart I use a tripwire to detect if there is a skeleton riding the spider. If it's just a spider it will not activate the tripwire and instead be set off to be killed. If it is a spider jockey then it will activate the tripwire and be sent to a storage area where the player can sort through them looking for special types.
Due to a bug in 1.9 and in 1.10 spider jockeys will not spawn in this farm, but instead only a skeleton will spawn.
This farm makes acquiring spider jockeys much easier than trying to find them naturally in the world. Enjoy!