Minecraft wiki entry for Combat, associated text: Stray cave spider jockey is the rarest spider jockey variants in Bedrock Edition, due it can only spawn from mineshaft with spawner viewed by sky in snowy biomes; such as ravine in snowy biomes that expose mineshaft spawner (snowy biomes also rare biome), the condition is very rarely met and if players found one like this, cave spider jockey only has 1% chance to spawn and 20% chance the rider will be normal skeleton, so the player is unlikely to find this mob. If the player encounters one, make sure to have milk as a stray can give slowness that makes the player difficult to escape while cave spider moves toward the player and inflict poison.